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fuchsia / third_party / rust / 217693a1f02ca6431a434926ff3417bdb6dbac2e / . / compiler / rustc_resolve / src / late / diagnostics.rs
blob: cf8db2267f41eee53ed746079d77b4856648e364 [file] [log] [blame]
// ignore-tidy-filelength
use std::borrow::Cow;
use std::iter;
use std::ops::Deref;
use rustc_ast::ptr::P;
use rustc_ast::visit::{FnCtxt, FnKind, LifetimeCtxt, Visitor, walk_ty};
use rustc_ast::{
self as ast, AssocItemKind, DUMMY_NODE_ID, Expr, ExprKind, GenericParam, GenericParamKind,
Item, ItemKind, MethodCall, NodeId, Path, PathSegment, Ty, TyKind,
};
use rustc_ast_pretty::pprust::where_bound_predicate_to_string;
use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
use rustc_errors::codes::*;
use rustc_errors::{
Applicability, Diag, ErrorGuaranteed, MultiSpan, SuggestionStyle, pluralize,
struct_span_code_err,
};
use rustc_hir as hir;
use rustc_hir::def::Namespace::{self, *};
use rustc_hir::def::{self, CtorKind, CtorOf, DefKind};
use rustc_hir::def_id::{CRATE_DEF_ID, DefId};
use rustc_hir::{MissingLifetimeKind, PrimTy};
use rustc_middle::ty;
use rustc_session::{Session, lint};
use rustc_span::edit_distance::{edit_distance, find_best_match_for_name};
use rustc_span::edition::Edition;
use rustc_span::hygiene::MacroKind;
use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
use thin_vec::ThinVec;
use tracing::debug;
use super::NoConstantGenericsReason;
use crate::diagnostics::{ImportSuggestion, LabelSuggestion, TypoSuggestion};
use crate::late::{
AliasPossibility, LateResolutionVisitor, LifetimeBinderKind, LifetimeRes, LifetimeRibKind,
LifetimeUseSet, QSelf, RibKind,
};
use crate::ty::fast_reject::SimplifiedType;
use crate::{
Module, ModuleKind, ModuleOrUniformRoot, PathResult, PathSource, Segment, errors,
path_names_to_string,
};
type Res = def::Res<ast::NodeId>;
/// A field or associated item from self type suggested in case of resolution failure.
enum AssocSuggestion {
Field(Span),
MethodWithSelf { called: bool },
AssocFn { called: bool },
AssocType,
AssocConst,
}
impl AssocSuggestion {
fn action(&self) -> &'static str {
match self {
AssocSuggestion::Field(_) => "use the available field",
AssocSuggestion::MethodWithSelf { called: true } => {
"call the method with the fully-qualified path"
}
AssocSuggestion::MethodWithSelf { called: false } => {
"refer to the method with the fully-qualified path"
}
AssocSuggestion::AssocFn { called: true } => "call the associated function",
AssocSuggestion::AssocFn { called: false } => "refer to the associated function",
AssocSuggestion::AssocConst => "use the associated `const`",
AssocSuggestion::AssocType => "use the associated type",
}
}
}
fn is_self_type(path: &[Segment], namespace: Namespace) -> bool {
namespace == TypeNS && path.len() == 1 && path[0].ident.name == kw::SelfUpper
}
fn is_self_value(path: &[Segment], namespace: Namespace) -> bool {
namespace == ValueNS && path.len() == 1 && path[0].ident.name == kw::SelfLower
}
/// Gets the stringified path for an enum from an `ImportSuggestion` for an enum variant.
fn import_candidate_to_enum_paths(suggestion: &ImportSuggestion) -> (String, String) {
let variant_path = &suggestion.path;
let variant_path_string = path_names_to_string(variant_path);
let path_len = suggestion.path.segments.len();
let enum_path = ast::Path {
span: suggestion.path.span,
segments: suggestion.path.segments[0..path_len - 1].iter().cloned().collect(),
tokens: None,
};
let enum_path_string = path_names_to_string(&enum_path);
(variant_path_string, enum_path_string)
}
/// Description of an elided lifetime.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug)]
pub(super) struct MissingLifetime {
/// Used to overwrite the resolution with the suggestion, to avoid cascading errors.
pub id: NodeId,
/// As we cannot yet emit lints in this crate and have to buffer them instead,
/// we need to associate each lint with some `NodeId`,
/// however for some `MissingLifetime`s their `NodeId`s are "fake",
/// in a sense that they are temporary and not get preserved down the line,
/// which means that the lints for those nodes will not get emitted.
/// To combat this, we can try to use some other `NodeId`s as a fallback option.
pub id_for_lint: NodeId,
/// Where to suggest adding the lifetime.
pub span: Span,
/// How the lifetime was introduced, to have the correct space and comma.
pub kind: MissingLifetimeKind,
/// Number of elided lifetimes, used for elision in path.
pub count: usize,
}
/// Description of the lifetimes appearing in a function parameter.
/// This is used to provide a literal explanation to the elision failure.
#[derive(Clone, Debug)]
pub(super) struct ElisionFnParameter {
/// The index of the argument in the original definition.
pub index: usize,
/// The name of the argument if it's a simple ident.
pub ident: Option<Ident>,
/// The number of lifetimes in the parameter.
pub lifetime_count: usize,
/// The span of the parameter.
pub span: Span,
}
/// Description of lifetimes that appear as candidates for elision.
/// This is used to suggest introducing an explicit lifetime.
#[derive(Debug)]
pub(super) enum LifetimeElisionCandidate {
/// This is not a real lifetime.
Ignore,
/// There is a named lifetime, we won't suggest anything.
Named,
Missing(MissingLifetime),
}
/// Only used for diagnostics.
#[derive(Debug)]
struct BaseError {
msg: String,
fallback_label: String,
span: Span,
span_label: Option<(Span, &'static str)>,
could_be_expr: bool,
suggestion: Option<(Span, &'static str, String)>,
module: Option<DefId>,
}
#[derive(Debug)]
enum TypoCandidate {
Typo(TypoSuggestion),
Shadowed(Res, Option<Span>),
None,
}
impl TypoCandidate {
fn to_opt_suggestion(self) -> Option<TypoSuggestion> {
match self {
TypoCandidate::Typo(sugg) => Some(sugg),
TypoCandidate::Shadowed(_, _) | TypoCandidate::None => None,
}
}
}
impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
fn make_base_error(
&mut self,
path: &[Segment],
span: Span,
source: PathSource<'_>,
res: Option<Res>,
) -> BaseError {
// Make the base error.
let mut expected = source.descr_expected();
let path_str = Segment::names_to_string(path);
let item_str = path.last().unwrap().ident;
if let Some(res) = res {
BaseError {
msg: format!("expected {}, found {} `{}`", expected, res.descr(), path_str),
fallback_label: format!("not a {expected}"),
span,
span_label: match res {
Res::Def(DefKind::TyParam, def_id) => {
Some((self.r.def_span(def_id), "found this type parameter"))
}
_ => None,
},
could_be_expr: match res {
Res::Def(DefKind::Fn, _) => {
// Verify whether this is a fn call or an Fn used as a type.
self.r
.tcx
.sess
.source_map()
.span_to_snippet(span)
.is_ok_and(|snippet| snippet.ends_with(')'))
}
Res::Def(
DefKind::Ctor(..) | DefKind::AssocFn | DefKind::Const | DefKind::AssocConst,
_,
)
| Res::SelfCtor(_)
| Res::PrimTy(_)
| Res::Local(_) => true,
_ => false,
},
suggestion: None,
module: None,
}
} else {
let mut span_label = None;
let item_ident = path.last().unwrap().ident;
let item_span = item_ident.span;
let (mod_prefix, mod_str, module, suggestion) = if path.len() == 1 {
debug!(?self.diag_metadata.current_impl_items);
debug!(?self.diag_metadata.current_function);
let suggestion = if self.current_trait_ref.is_none()
&& let Some((fn_kind, _)) = self.diag_metadata.current_function
&& let Some(FnCtxt::Assoc(_)) = fn_kind.ctxt()
&& let FnKind::Fn(_, _, _, ast::Fn { sig, .. }) = fn_kind
&& let Some(items) = self.diag_metadata.current_impl_items
&& let Some(item) = items.iter().find(|i| {
i.ident.name == item_str.name
// Don't suggest if the item is in Fn signature arguments (#112590).
&& !sig.span.contains(item_span)
}) {
let sp = item_span.shrink_to_lo();
// Account for `Foo { field }` when suggesting `self.field` so we result on
// `Foo { field: self.field }`.
let field = match source {
PathSource::Expr(Some(Expr { kind: ExprKind::Struct(expr), .. })) => {
expr.fields.iter().find(|f| f.ident == item_ident)
}
_ => None,
};
let pre = if let Some(field) = field
&& field.is_shorthand
{
format!("{item_ident}: ")
} else {
String::new()
};
// Ensure we provide a structured suggestion for an assoc fn only for
// expressions that are actually a fn call.
let is_call = match field {
Some(ast::ExprField { expr, .. }) => {
matches!(expr.kind, ExprKind::Call(..))
}
_ => matches!(
source,
PathSource::Expr(Some(Expr { kind: ExprKind::Call(..), .. })),
),
};
match &item.kind {
AssocItemKind::Fn(fn_)
if (!sig.decl.has_self() || !is_call) && fn_.sig.decl.has_self() =>
{
// Ensure that we only suggest `self.` if `self` is available,
// you can't call `fn foo(&self)` from `fn bar()` (#115992).
// We also want to mention that the method exists.
span_label = Some((
item.ident.span,
"a method by that name is available on `Self` here",
));
None
}
AssocItemKind::Fn(fn_) if !fn_.sig.decl.has_self() && !is_call => {
span_label = Some((
item.ident.span,
"an associated function by that name is available on `Self` here",
));
None
}
AssocItemKind::Fn(fn_) if fn_.sig.decl.has_self() => {
Some((sp, "consider using the method on `Self`", format!("{pre}self.")))
}
AssocItemKind::Fn(_) => Some((
sp,
"consider using the associated function on `Self`",
format!("{pre}Self::"),
)),
AssocItemKind::Const(..) => Some((
sp,
"consider using the associated constant on `Self`",
format!("{pre}Self::"),
)),
_ => None,
}
} else {
None
};
(String::new(), "this scope".to_string(), None, suggestion)
} else if path.len() == 2 && path[0].ident.name == kw::PathRoot {
if self.r.tcx.sess.edition() > Edition::Edition2015 {
// In edition 2018 onwards, the `::foo` syntax may only pull from the extern prelude
// which overrides all other expectations of item type
expected = "crate";
(String::new(), "the list of imported crates".to_string(), None, None)
} else {
(
String::new(),
"the crate root".to_string(),
Some(CRATE_DEF_ID.to_def_id()),
None,
)
}
} else if path.len() == 2 && path[0].ident.name == kw::Crate {
(String::new(), "the crate root".to_string(), Some(CRATE_DEF_ID.to_def_id()), None)
} else {
let mod_path = &path[..path.len() - 1];
let mod_res = self.resolve_path(mod_path, Some(TypeNS), None);
let mod_prefix = match mod_res {
PathResult::Module(ModuleOrUniformRoot::Module(module)) => module.res(),
_ => None,
};
let module_did = mod_prefix.as_ref().and_then(Res::mod_def_id);
let mod_prefix =
mod_prefix.map_or_else(String::new, |res| (format!("{} ", res.descr())));
(mod_prefix, format!("`{}`", Segment::names_to_string(mod_path)), module_did, None)
};
let (fallback_label, suggestion) = if path_str == "async"
&& expected.starts_with("struct")
{
("`async` blocks are only allowed in Rust 2018 or later".to_string(), suggestion)
} else {
// check if we are in situation of typo like `True` instead of `true`.
let override_suggestion =
if ["true", "false"].contains(&item_str.to_string().to_lowercase().as_str()) {
let item_typo = item_str.to_string().to_lowercase();
Some((item_span, "you may want to use a bool value instead", item_typo))
// FIXME(vincenzopalazzo): make the check smarter,
// and maybe expand with levenshtein distance checks
} else if item_str.as_str() == "printf" {
Some((
item_span,
"you may have meant to use the `print` macro",
"print!".to_owned(),
))
} else {
suggestion
};
(format!("not found in {mod_str}"), override_suggestion)
};
BaseError {
msg: format!("cannot find {expected} `{item_str}` in {mod_prefix}{mod_str}"),
fallback_label,
span: item_span,
span_label,
could_be_expr: false,
suggestion,
module,
}
}
}
/// Try to suggest for a module path that cannot be resolved.
/// Such as `fmt::Debug` where `fmt` is not resolved without importing,
/// here we search with `lookup_import_candidates` for a module named `fmt`
/// with `TypeNS` as namespace.
///
/// We need a separate function here because we won't suggest for a path with single segment
/// and we won't change `SourcePath` api `is_expected` to match `Type` with `DefKind::Mod`
pub(crate) fn smart_resolve_partial_mod_path_errors(
&mut self,
prefix_path: &[Segment],
following_seg: Option<&Segment>,
) -> Vec<ImportSuggestion> {
if let Some(segment) = prefix_path.last()
&& let Some(following_seg) = following_seg
{
let candidates = self.r.lookup_import_candidates(
segment.ident,
Namespace::TypeNS,
&self.parent_scope,
&|res: Res| matches!(res, Res::Def(DefKind::Mod, _)),
);
// double check next seg is valid
candidates
.into_iter()
.filter(|candidate| {
if let Some(def_id) = candidate.did
&& let Some(module) = self.r.get_module(def_id)
{
Some(def_id) != self.parent_scope.module.opt_def_id()
&& self
.r
.resolutions(module)
.borrow()
.iter()
.any(|(key, _r)| key.ident.name == following_seg.ident.name)
} else {
false
}
})
.collect::<Vec<_>>()
} else {
Vec::new()
}
}
/// Handles error reporting for `smart_resolve_path_fragment` function.
/// Creates base error and amends it with one short label and possibly some longer helps/notes.
pub(crate) fn smart_resolve_report_errors(
&mut self,
path: &[Segment],
following_seg: Option<&Segment>,
span: Span,
source: PathSource<'_>,
res: Option<Res>,
qself: Option<&QSelf>,
) -> (Diag<'tcx>, Vec<ImportSuggestion>) {
debug!(?res, ?source);
let base_error = self.make_base_error(path, span, source, res);
let code = source.error_code(res.is_some());
let mut err = self.r.dcx().struct_span_err(base_error.span, base_error.msg.clone());
err.code(code);
// Try to get the span of the identifier within the path's syntax context
// (if that's different).
if let Some(within_macro_span) =
base_error.span.within_macro(span, self.r.tcx.sess.source_map())
{
err.span_label(within_macro_span, "due to this macro variable");
}
self.detect_missing_binding_available_from_pattern(&mut err, path, following_seg);
self.suggest_at_operator_in_slice_pat_with_range(&mut err, path);
self.suggest_swapping_misplaced_self_ty_and_trait(&mut err, source, res, base_error.span);
if let Some((span, label)) = base_error.span_label {
err.span_label(span, label);
}
if let Some(ref sugg) = base_error.suggestion {
err.span_suggestion_verbose(sugg.0, sugg.1, &sugg.2, Applicability::MaybeIncorrect);
}
self.suggest_changing_type_to_const_param(&mut err, res, source, span);
self.explain_functions_in_pattern(&mut err, res, source);
if self.suggest_pattern_match_with_let(&mut err, source, span) {
// Fallback label.
err.span_label(base_error.span, base_error.fallback_label);
return (err, Vec::new());
}
self.suggest_self_or_self_ref(&mut err, path, span);
self.detect_assoc_type_constraint_meant_as_path(&mut err, &base_error);
self.detect_rtn_with_fully_qualified_path(
&mut err,
path,
following_seg,
span,
source,
res,
qself,
);
if self.suggest_self_ty(&mut err, source, path, span)
|| self.suggest_self_value(&mut err, source, path, span)
{
return (err, Vec::new());
}
let (found, suggested_candidates, mut candidates) = self.try_lookup_name_relaxed(
&mut err,
source,
path,
following_seg,
span,
res,
&base_error,
);
if found {
return (err, candidates);
}
if self.suggest_shadowed(&mut err, source, path, following_seg, span) {
// if there is already a shadowed name, don'suggest candidates for importing
candidates.clear();
}
let mut fallback = self.suggest_trait_and_bounds(&mut err, source, res, span, &base_error);
fallback |= self.suggest_typo(
&mut err,
source,
path,
following_seg,
span,
&base_error,
suggested_candidates,
);
if fallback {
// Fallback label.
err.span_label(base_error.span, base_error.fallback_label);
}
self.err_code_special_cases(&mut err, source, path, span);
if let Some(module) = base_error.module {
self.r.find_cfg_stripped(&mut err, &path.last().unwrap().ident.name, module);
}
(err, candidates)
}
fn detect_rtn_with_fully_qualified_path(
&self,
err: &mut Diag<'_>,
path: &[Segment],
following_seg: Option<&Segment>,
span: Span,
source: PathSource<'_>,
res: Option<Res>,
qself: Option<&QSelf>,
) {
if let Some(Res::Def(DefKind::AssocFn, _)) = res
&& let PathSource::TraitItem(TypeNS) = source
&& let None = following_seg
&& let Some(qself) = qself
&& let TyKind::Path(None, ty_path) = &qself.ty.kind
&& ty_path.segments.len() == 1
&& self.diag_metadata.current_where_predicate.is_some()
{
err.span_suggestion_verbose(
span,
"you might have meant to use the return type notation syntax",
format!("{}::{}(..)", ty_path.segments[0].ident, path[path.len() - 1].ident),
Applicability::MaybeIncorrect,
);
}
}
fn detect_assoc_type_constraint_meant_as_path(
&self,
err: &mut Diag<'_>,
base_error: &BaseError,
) {
let Some(ty) = self.diag_metadata.current_type_path else {
return;
};
let TyKind::Path(_, path) = &ty.kind else {
return;
};
for segment in &path.segments {
let Some(params) = &segment.args else {
continue;
};
let ast::GenericArgs::AngleBracketed(params) = params.deref() else {
continue;
};
for param in &params.args {
let ast::AngleBracketedArg::Constraint(constraint) = param else {
continue;
};
let ast::AssocItemConstraintKind::Bound { bounds } = &constraint.kind else {
continue;
};
for bound in bounds {
let ast::GenericBound::Trait(trait_ref) = bound else {
continue;
};
if trait_ref.modifiers == ast::TraitBoundModifiers::NONE
&& base_error.span == trait_ref.span
{
err.span_suggestion_verbose(
constraint.ident.span.between(trait_ref.span),
"you might have meant to write a path instead of an associated type bound",
"::",
Applicability::MachineApplicable,
);
}
}
}
}
}
fn suggest_self_or_self_ref(&mut self, err: &mut Diag<'_>, path: &[Segment], span: Span) {
if !self.self_type_is_available() {
return;
}
let Some(path_last_segment) = path.last() else { return };
let item_str = path_last_segment.ident;
// Emit help message for fake-self from other languages (e.g., `this` in JavaScript).
if ["this", "my"].contains(&item_str.as_str()) {
err.span_suggestion_short(
span,
"you might have meant to use `self` here instead",
"self",
Applicability::MaybeIncorrect,
);
if !self.self_value_is_available(path[0].ident.span) {
if let Some((FnKind::Fn(_, _, _, ast::Fn { sig, .. }), fn_span)) =
&self.diag_metadata.current_function
{
let (span, sugg) = if let Some(param) = sig.decl.inputs.get(0) {
(param.span.shrink_to_lo(), "&self, ")
} else {
(
self.r
.tcx
.sess
.source_map()
.span_through_char(*fn_span, '(')
.shrink_to_hi(),
"&self",
)
};
err.span_suggestion_verbose(
span,
"if you meant to use `self`, you are also missing a `self` receiver \
argument",
sugg,
Applicability::MaybeIncorrect,
);
}
}
}
}
fn try_lookup_name_relaxed(
&mut self,
err: &mut Diag<'_>,
source: PathSource<'_>,
path: &[Segment],
following_seg: Option<&Segment>,
span: Span,
res: Option<Res>,
base_error: &BaseError,
) -> (bool, FxHashSet<String>, Vec<ImportSuggestion>) {
let span = match following_seg {
Some(_) if path[0].ident.span.eq_ctxt(path[path.len() - 1].ident.span) => {
// The path `span` that comes in includes any following segments, which we don't
// want to replace in the suggestions.
path[0].ident.span.to(path[path.len() - 1].ident.span)
}
_ => span,
};
let mut suggested_candidates = FxHashSet::default();
// Try to lookup name in more relaxed fashion for better error reporting.
let ident = path.last().unwrap().ident;
let is_expected = &|res| source.is_expected(res);
let ns = source.namespace();
let is_enum_variant = &|res| matches!(res, Res::Def(DefKind::Variant, _));
let path_str = Segment::names_to_string(path);
let ident_span = path.last().map_or(span, |ident| ident.ident.span);
let mut candidates = self
.r
.lookup_import_candidates(ident, ns, &self.parent_scope, is_expected)
.into_iter()
.filter(|ImportSuggestion { did, .. }| {
match (did, res.and_then(|res| res.opt_def_id())) {
(Some(suggestion_did), Some(actual_did)) => *suggestion_did != actual_did,
_ => true,
}
})
.collect::<Vec<_>>();
// Try to filter out intrinsics candidates, as long as we have
// some other candidates to suggest.
let intrinsic_candidates: Vec<_> = candidates
.extract_if(.., |sugg| {
let path = path_names_to_string(&sugg.path);
path.starts_with("core::intrinsics::") || path.starts_with("std::intrinsics::")
})
.collect();
if candidates.is_empty() {
// Put them back if we have no more candidates to suggest...
candidates = intrinsic_candidates;
}
let crate_def_id = CRATE_DEF_ID.to_def_id();
if candidates.is_empty() && is_expected(Res::Def(DefKind::Enum, crate_def_id)) {
let mut enum_candidates: Vec<_> = self
.r
.lookup_import_candidates(ident, ns, &self.parent_scope, is_enum_variant)
.into_iter()
.map(|suggestion| import_candidate_to_enum_paths(&suggestion))
.filter(|(_, enum_ty_path)| !enum_ty_path.starts_with("std::prelude::"))
.collect();
if !enum_candidates.is_empty() {
enum_candidates.sort();
// Contextualize for E0412 "cannot find type", but don't belabor the point
// (that it's a variant) for E0573 "expected type, found variant".
let preamble = if res.is_none() {
let others = match enum_candidates.len() {
1 => String::new(),
2 => " and 1 other".to_owned(),
n => format!(" and {n} others"),
};
format!("there is an enum variant `{}`{}; ", enum_candidates[0].0, others)
} else {
String::new()
};
let msg = format!("{preamble}try using the variant's enum");
suggested_candidates.extend(
enum_candidates
.iter()
.map(|(_variant_path, enum_ty_path)| enum_ty_path.clone()),
);
err.span_suggestions(
span,
msg,
enum_candidates.into_iter().map(|(_variant_path, enum_ty_path)| enum_ty_path),
Applicability::MachineApplicable,
);
}
}
// Try finding a suitable replacement.
let typo_sugg = self
.lookup_typo_candidate(path, following_seg, source.namespace(), is_expected)
.to_opt_suggestion()
.filter(|sugg| !suggested_candidates.contains(sugg.candidate.as_str()));
if let [segment] = path
&& !matches!(source, PathSource::Delegation)
&& self.self_type_is_available()
{
if let Some(candidate) =
self.lookup_assoc_candidate(ident, ns, is_expected, source.is_call())
{
let self_is_available = self.self_value_is_available(segment.ident.span);
// Account for `Foo { field }` when suggesting `self.field` so we result on
// `Foo { field: self.field }`.
let pre = match source {
PathSource::Expr(Some(Expr { kind: ExprKind::Struct(expr), .. }))
if expr
.fields
.iter()
.any(|f| f.ident == segment.ident && f.is_shorthand) =>
{
format!("{path_str}: ")
}
_ => String::new(),
};
match candidate {
AssocSuggestion::Field(field_span) => {
if self_is_available {
err.span_suggestion_verbose(
span.shrink_to_lo(),
"you might have meant to use the available field",
format!("{pre}self."),
Applicability::MachineApplicable,
);
} else {
err.span_label(field_span, "a field by that name exists in `Self`");
}
}
AssocSuggestion::MethodWithSelf { called } if self_is_available => {
let msg = if called {
"you might have meant to call the method"
} else {
"you might have meant to refer to the method"
};
err.span_suggestion_verbose(
span.shrink_to_lo(),
msg,
"self.",
Applicability::MachineApplicable,
);
}
AssocSuggestion::MethodWithSelf { .. }
| AssocSuggestion::AssocFn { .. }
| AssocSuggestion::AssocConst
| AssocSuggestion::AssocType => {
err.span_suggestion_verbose(
span.shrink_to_lo(),
format!("you might have meant to {}", candidate.action()),
"Self::",
Applicability::MachineApplicable,
);
}
}
self.r.add_typo_suggestion(err, typo_sugg, ident_span);
return (true, suggested_candidates, candidates);
}
// If the first argument in call is `self` suggest calling a method.
if let Some((call_span, args_span)) = self.call_has_self_arg(source) {
let mut args_snippet = String::new();
if let Some(args_span) = args_span {
if let Ok(snippet) = self.r.tcx.sess.source_map().span_to_snippet(args_span) {
args_snippet = snippet;
}
}
err.span_suggestion(
call_span,
format!("try calling `{ident}` as a method"),
format!("self.{path_str}({args_snippet})"),
Applicability::MachineApplicable,
);
return (true, suggested_candidates, candidates);
}
}
// Try context-dependent help if relaxed lookup didn't work.
if let Some(res) = res {
if self.smart_resolve_context_dependent_help(
err,
span,
source,
path,
res,
&path_str,
&base_error.fallback_label,
) {
// We do this to avoid losing a secondary span when we override the main error span.
self.r.add_typo_suggestion(err, typo_sugg, ident_span);
return (true, suggested_candidates, candidates);
}
}
// Try to find in last block rib
if let Some(rib) = &self.last_block_rib
&& let RibKind::Normal = rib.kind
{
for (ident, &res) in &rib.bindings {
if let Res::Local(_) = res
&& path.len() == 1
&& ident.span.eq_ctxt(path[0].ident.span)
&& ident.name == path[0].ident.name
{
err.span_help(
ident.span,
format!("the binding `{path_str}` is available in a different scope in the same function"),
);
return (true, suggested_candidates, candidates);
}
}
}
if candidates.is_empty() {
candidates = self.smart_resolve_partial_mod_path_errors(path, following_seg);
}
(false, suggested_candidates, candidates)
}
fn suggest_trait_and_bounds(
&mut self,
err: &mut Diag<'_>,
source: PathSource<'_>,
res: Option<Res>,
span: Span,
base_error: &BaseError,
) -> bool {
let is_macro =
base_error.span.from_expansion() && base_error.span.desugaring_kind().is_none();
let mut fallback = false;
if let (
PathSource::Trait(AliasPossibility::Maybe),
Some(Res::Def(DefKind::Struct | DefKind::Enum | DefKind::Union, _)),
false,
) = (source, res, is_macro)
{
if let Some(bounds @ [first_bound, .., last_bound]) =
self.diag_metadata.current_trait_object
{
fallback = true;
let spans: Vec<Span> = bounds
.iter()
.map(|bound| bound.span())
.filter(|&sp| sp != base_error.span)
.collect();
let start_span = first_bound.span();
// `end_span` is the end of the poly trait ref (Foo + 'baz + Bar><)
let end_span = last_bound.span();
// `last_bound_span` is the last bound of the poly trait ref (Foo + >'baz< + Bar)
let last_bound_span = spans.last().cloned().unwrap();
let mut multi_span: MultiSpan = spans.clone().into();
for sp in spans {
let msg = if sp == last_bound_span {
format!(
"...because of {these} bound{s}",
these = pluralize!("this", bounds.len() - 1),
s = pluralize!(bounds.len() - 1),
)
} else {
String::new()
};
multi_span.push_span_label(sp, msg);
}
multi_span.push_span_label(base_error.span, "expected this type to be a trait...");
err.span_help(
multi_span,
"`+` is used to constrain a \"trait object\" type with lifetimes or \
auto-traits; structs and enums can't be bound in that way",
);
if bounds.iter().all(|bound| match bound {
ast::GenericBound::Outlives(_) | ast::GenericBound::Use(..) => true,
ast::GenericBound::Trait(tr) => tr.span == base_error.span,
}) {
let mut sugg = vec![];
if base_error.span != start_span {
sugg.push((start_span.until(base_error.span), String::new()));
}
if base_error.span != end_span {
sugg.push((base_error.span.shrink_to_hi().to(end_span), String::new()));
}
err.multipart_suggestion(
"if you meant to use a type and not a trait here, remove the bounds",
sugg,
Applicability::MaybeIncorrect,
);
}
}
}
fallback |= self.restrict_assoc_type_in_where_clause(span, err);
fallback
}
fn suggest_typo(
&mut self,
err: &mut Diag<'_>,
source: PathSource<'_>,
path: &[Segment],
following_seg: Option<&Segment>,
span: Span,
base_error: &BaseError,
suggested_candidates: FxHashSet<String>,
) -> bool {
let is_expected = &|res| source.is_expected(res);
let ident_span = path.last().map_or(span, |ident| ident.ident.span);
let typo_sugg =
self.lookup_typo_candidate(path, following_seg, source.namespace(), is_expected);
let mut fallback = false;
let typo_sugg = typo_sugg
.to_opt_suggestion()
.filter(|sugg| !suggested_candidates.contains(sugg.candidate.as_str()));
if !self.r.add_typo_suggestion(err, typo_sugg, ident_span) {
fallback = true;
match self.diag_metadata.current_let_binding {
Some((pat_sp, Some(ty_sp), None))
if ty_sp.contains(base_error.span) && base_error.could_be_expr =>
{
err.span_suggestion_short(
pat_sp.between(ty_sp),
"use `=` if you meant to assign",
" = ",
Applicability::MaybeIncorrect,
);
}
_ => {}
}
// If the trait has a single item (which wasn't matched by the algorithm), suggest it
let suggestion = self.get_single_associated_item(path, &source, is_expected);
self.r.add_typo_suggestion(err, suggestion, ident_span);
}
if self.let_binding_suggestion(err, ident_span) {
fallback = false;
}
fallback
}
fn suggest_shadowed(
&mut self,
err: &mut Diag<'_>,
source: PathSource<'_>,
path: &[Segment],
following_seg: Option<&Segment>,
span: Span,
) -> bool {
let is_expected = &|res| source.is_expected(res);
let typo_sugg =
self.lookup_typo_candidate(path, following_seg, source.namespace(), is_expected);
let is_in_same_file = &|sp1, sp2| {
let source_map = self.r.tcx.sess.source_map();
let file1 = source_map.span_to_filename(sp1);
let file2 = source_map.span_to_filename(sp2);
file1 == file2
};
// print 'you might have meant' if the candidate is (1) is a shadowed name with
// accessible definition and (2) either defined in the same crate as the typo
// (could be in a different file) or introduced in the same file as the typo
// (could belong to a different crate)
if let TypoCandidate::Shadowed(res, Some(sugg_span)) = typo_sugg
&& res.opt_def_id().is_some_and(|id| id.is_local() || is_in_same_file(span, sugg_span))
{
err.span_label(
sugg_span,
format!("you might have meant to refer to this {}", res.descr()),
);
return true;
}
false
}
fn err_code_special_cases(
&mut self,
err: &mut Diag<'_>,
source: PathSource<'_>,
path: &[Segment],
span: Span,
) {
if let Some(err_code) = err.code {
if err_code == E0425 {
for label_rib in &self.label_ribs {
for (label_ident, node_id) in &label_rib.bindings {
let ident = path.last().unwrap().ident;
if format!("'{ident}") == label_ident.to_string() {
err.span_label(label_ident.span, "a label with a similar name exists");
if let PathSource::Expr(Some(Expr {
kind: ExprKind::Break(None, Some(_)),
..
})) = source
{
err.span_suggestion(
span,
"use the similarly named label",
label_ident.name,
Applicability::MaybeIncorrect,
);
// Do not lint against unused label when we suggest them.
self.diag_metadata.unused_labels.swap_remove(node_id);
}
}
}
}
} else if err_code == E0412 {
if let Some(correct) = Self::likely_rust_type(path) {
err.span_suggestion(
span,
"perhaps you intended to use this type",
correct,
Applicability::MaybeIncorrect,
);
}
}
}
}
/// Emit special messages for unresolved `Self` and `self`.
fn suggest_self_ty(
&mut self,
err: &mut Diag<'_>,
source: PathSource<'_>,
path: &[Segment],
span: Span,
) -> bool {
if !is_self_type(path, source.namespace()) {
return false;
}
err.code(E0411);
err.span_label(span, "`Self` is only available in impls, traits, and type definitions");
if let Some(item_kind) = self.diag_metadata.current_item {
if !item_kind.ident.span.is_dummy() {
err.span_label(
item_kind.ident.span,
format!(
"`Self` not allowed in {} {}",
item_kind.kind.article(),
item_kind.kind.descr()
),
);
}
}
true
}
fn suggest_self_value(
&mut self,
err: &mut Diag<'_>,
source: PathSource<'_>,
path: &[Segment],
span: Span,
) -> bool {
if !is_self_value(path, source.namespace()) {
return false;
}
debug!("smart_resolve_path_fragment: E0424, source={:?}", source);
err.code(E0424);
err.span_label(
span,
match source {
PathSource::Pat => {
"`self` value is a keyword and may not be bound to variables or shadowed"
}
_ => "`self` value is a keyword only available in methods with a `self` parameter",
},
);
let is_assoc_fn = self.self_type_is_available();
let self_from_macro = "a `self` parameter, but a macro invocation can only \
access identifiers it receives from parameters";
if let Some((fn_kind, span)) = &self.diag_metadata.current_function {
// The current function has a `self` parameter, but we were unable to resolve
// a reference to `self`. This can only happen if the `self` identifier we
// are resolving came from a different hygiene context.
if fn_kind.decl().inputs.get(0).is_some_and(|p| p.is_self()) {
err.span_label(*span, format!("this function has {self_from_macro}"));
} else {
let doesnt = if is_assoc_fn {
let (span, sugg) = fn_kind
.decl()
.inputs
.get(0)
.map(|p| (p.span.shrink_to_lo(), "&self, "))
.unwrap_or_else(|| {
// Try to look for the "(" after the function name, if possible.
// This avoids placing the suggestion into the visibility specifier.
let span = fn_kind
.ident()
.map_or(*span, |ident| span.with_lo(ident.span.hi()));
(
self.r
.tcx
.sess
.source_map()
.span_through_char(span, '(')
.shrink_to_hi(),
"&self",
)
});
err.span_suggestion_verbose(
span,
"add a `self` receiver parameter to make the associated `fn` a method",
sugg,
Applicability::MaybeIncorrect,
);
"doesn't"
} else {
"can't"
};
if let Some(ident) = fn_kind.ident() {
err.span_label(
ident.span,
format!("this function {doesnt} have a `self` parameter"),
);
}
}
} else if let Some(item_kind) = self.diag_metadata.current_item {
if matches!(item_kind.kind, ItemKind::Delegation(..)) {
err.span_label(item_kind.span, format!("delegation supports {self_from_macro}"));
} else {
err.span_label(
item_kind.ident.span,
format!(
"`self` not allowed in {} {}",
item_kind.kind.article(),
item_kind.kind.descr()
),
);
}
}
true
}
fn detect_missing_binding_available_from_pattern(
&mut self,
err: &mut Diag<'_>,
path: &[Segment],
following_seg: Option<&Segment>,
) {
let [segment] = path else { return };
let None = following_seg else { return };
for rib in self.ribs[ValueNS].iter().rev() {
let patterns_with_skipped_bindings = self.r.tcx.with_stable_hashing_context(|hcx| {
rib.patterns_with_skipped_bindings.to_sorted(&hcx, true)
});
for (def_id, spans) in patterns_with_skipped_bindings {
if let DefKind::Struct | DefKind::Variant = self.r.tcx.def_kind(*def_id)
&& let Some(fields) = self.r.field_idents(*def_id)
{
for field in fields {
if field.name == segment.ident.name {
if spans.iter().all(|(_, had_error)| had_error.is_err()) {
// This resolution error will likely be fixed by fixing a
// syntax error in a pattern, so it is irrelevant to the user.
let multispan: MultiSpan =
spans.iter().map(|(s, _)| *s).collect::<Vec<_>>().into();
err.span_note(
multispan,
"this pattern had a recovered parse error which likely lost \
the expected fields",
);
err.downgrade_to_delayed_bug();
}
let ty = self.r.tcx.item_name(*def_id);
for (span, _) in spans {
err.span_label(
*span,
format!(
"this pattern doesn't include `{field}`, which is \
available in `{ty}`",
),
);
}
}
}
}
}
}
}
fn suggest_at_operator_in_slice_pat_with_range(
&mut self,
err: &mut Diag<'_>,
path: &[Segment],
) {
let Some(pat) = self.diag_metadata.current_pat else { return };
let (bound, side, range) = match &pat.kind {
ast::PatKind::Range(Some(bound), None, range) => (bound, Side::Start, range),
ast::PatKind::Range(None, Some(bound), range) => (bound, Side::End, range),
_ => return,
};
if let ExprKind::Path(None, range_path) = &bound.kind
&& let [segment] = &range_path.segments[..]
&& let [s] = path
&& segment.ident == s.ident
&& segment.ident.span.eq_ctxt(range.span)
{
// We've encountered `[first, rest..]` (#88404) or `[first, ..rest]` (#120591)
// where the user might have meant `[first, rest @ ..]`.
let (span, snippet) = match side {
Side::Start => (segment.ident.span.between(range.span), " @ ".into()),
Side::End => (range.span.to(segment.ident.span), format!("{} @ ..", segment.ident)),
};
err.subdiagnostic(errors::UnexpectedResUseAtOpInSlicePatWithRangeSugg {
span,
ident: segment.ident,
snippet,
});
}
enum Side {
Start,
End,
}
}
fn suggest_swapping_misplaced_self_ty_and_trait(
&mut self,
err: &mut Diag<'_>,
source: PathSource<'_>,
res: Option<Res>,
span: Span,
) {
if let Some((trait_ref, self_ty)) =
self.diag_metadata.currently_processing_impl_trait.clone()
&& let TyKind::Path(_, self_ty_path) = &self_ty.kind
&& let PathResult::Module(ModuleOrUniformRoot::Module(module)) =
self.resolve_path(&Segment::from_path(self_ty_path), Some(TypeNS), None)
&& let ModuleKind::Def(DefKind::Trait, ..) = module.kind
&& trait_ref.path.span == span
&& let PathSource::Trait(_) = source
&& let Some(Res::Def(DefKind::Struct | DefKind::Enum | DefKind::Union, _)) = res
&& let Ok(self_ty_str) = self.r.tcx.sess.source_map().span_to_snippet(self_ty.span)
&& let Ok(trait_ref_str) =
self.r.tcx.sess.source_map().span_to_snippet(trait_ref.path.span)
{
err.multipart_suggestion(
"`impl` items mention the trait being implemented first and the type it is being implemented for second",
vec![(trait_ref.path.span, self_ty_str), (self_ty.span, trait_ref_str)],
Applicability::MaybeIncorrect,
);
}
}
fn explain_functions_in_pattern(
&mut self,
err: &mut Diag<'_>,
res: Option<Res>,
source: PathSource<'_>,
) {
let PathSource::TupleStruct(_, _) = source else { return };
let Some(Res::Def(DefKind::Fn, _)) = res else { return };
err.primary_message("expected a pattern, found a function call");
err.note("function calls are not allowed in patterns: <https://doc.rust-lang.org/book/ch19-00-patterns.html>");
}
fn suggest_changing_type_to_const_param(
&mut self,
err: &mut Diag<'_>,
res: Option<Res>,
source: PathSource<'_>,
span: Span,
) {
let PathSource::Trait(_) = source else { return };
// We don't include `DefKind::Str` and `DefKind::AssocTy` as they can't be reached here anyway.
let applicability = match res {
Some(Res::PrimTy(PrimTy::Int(_) | PrimTy::Uint(_) | PrimTy::Bool | PrimTy::Char)) => {
Applicability::MachineApplicable
}
// FIXME(const_generics): Add `DefKind::TyParam` and `SelfTyParam` once we support generic
// const generics. Of course, `Struct` and `Enum` may contain ty params, too, but the
// benefits of including them here outweighs the small number of false positives.
Some(Res::Def(DefKind::Struct | DefKind::Enum, _))
if self.r.tcx.features().adt_const_params() =>
{
Applicability::MaybeIncorrect
}
_ => return,
};
let Some(item) = self.diag_metadata.current_item else { return };
let Some(generics) = item.kind.generics() else { return };
let param = generics.params.iter().find_map(|param| {
// Only consider type params with exactly one trait bound.
if let [bound] = &*param.bounds
&& let ast::GenericBound::Trait(tref) = bound
&& tref.modifiers == ast::TraitBoundModifiers::NONE
&& tref.span == span
&& param.ident.span.eq_ctxt(span)
{
Some(param.ident.span)
} else {
None
}
});
if let Some(param) = param {
err.subdiagnostic(errors::UnexpectedResChangeTyToConstParamSugg {
span: param.shrink_to_lo(),
applicability,
});
}
}
fn suggest_pattern_match_with_let(
&mut self,
err: &mut Diag<'_>,
source: PathSource<'_>,
span: Span,
) -> bool {
if let PathSource::Expr(_) = source
&& let Some(Expr { span: expr_span, kind: ExprKind::Assign(lhs, _, _), .. }) =
self.diag_metadata.in_if_condition
{
// Icky heuristic so we don't suggest:
// `if (i + 2) = 2` => `if let (i + 2) = 2` (approximately pattern)
// `if 2 = i` => `if let 2 = i` (lhs needs to contain error span)
if lhs.is_approximately_pattern() && lhs.span.contains(span) {
err.span_suggestion_verbose(
expr_span.shrink_to_lo(),
"you might have meant to use pattern matching",
"let ",
Applicability::MaybeIncorrect,
);
return true;
}
}
false
}
fn get_single_associated_item(
&mut self,
path: &[Segment],
source: &PathSource<'_>,
filter_fn: &impl Fn(Res) -> bool,
) -> Option<TypoSuggestion> {
if let crate::PathSource::TraitItem(_) = source {
let mod_path = &path[..path.len() - 1];
if let PathResult::Module(ModuleOrUniformRoot::Module(module)) =
self.resolve_path(mod_path, None, None)
{
let resolutions = self.r.resolutions(module).borrow();
let targets: Vec<_> =
resolutions
.iter()
.filter_map(|(key, resolution)| {
resolution.borrow().binding.map(|binding| binding.res()).and_then(
|res| if filter_fn(res) { Some((key, res)) } else { None },
)
})
.collect();
if let [target] = targets.as_slice() {
return Some(TypoSuggestion::single_item_from_ident(target.0.ident, target.1));
}
}
}
None
}
/// Given `where <T as Bar>::Baz: String`, suggest `where T: Bar<Baz = String>`.
fn restrict_assoc_type_in_where_clause(&mut self, span: Span, err: &mut Diag<'_>) -> bool {
// Detect that we are actually in a `where` predicate.
let (bounded_ty, bounds, where_span) = if let Some(ast::WherePredicate {
kind:
ast::WherePredicateKind::BoundPredicate(ast::WhereBoundPredicate {
bounded_ty,
bound_generic_params,
bounds,
}),
span,
..
}) = self.diag_metadata.current_where_predicate
{
if !bound_generic_params.is_empty() {
return false;
}
(bounded_ty, bounds, span)
} else {
return false;
};
// Confirm that the target is an associated type.
let (ty, _, path) = if let ast::TyKind::Path(Some(qself), path) = &bounded_ty.kind {
// use this to verify that ident is a type param.
let Some(partial_res) = self.r.partial_res_map.get(&bounded_ty.id) else {
return false;
};
if !matches!(
partial_res.full_res(),
Some(hir::def::Res::Def(hir::def::DefKind::AssocTy, _))
) {
return false;
}
(&qself.ty, qself.position, path)
} else {
return false;
};
let peeled_ty = ty.peel_refs();
if let ast::TyKind::Path(None, type_param_path) = &peeled_ty.kind {
// Confirm that the `SelfTy` is a type parameter.
let Some(partial_res) = self.r.partial_res_map.get(&peeled_ty.id) else {
return false;
};
if !matches!(
partial_res.full_res(),
Some(hir::def::Res::Def(hir::def::DefKind::TyParam, _))
) {
return false;
}
if let (
[ast::PathSegment { args: None, .. }],
[ast::GenericBound::Trait(poly_trait_ref)],
) = (&type_param_path.segments[..], &bounds[..])
&& poly_trait_ref.modifiers == ast::TraitBoundModifiers::NONE
{
if let [ast::PathSegment { ident, args: None, .. }] =
&poly_trait_ref.trait_ref.path.segments[..]
{
if ident.span == span {
let Some(new_where_bound_predicate) =
mk_where_bound_predicate(path, poly_trait_ref, ty)
else {
return false;
};
err.span_suggestion_verbose(
*where_span,
format!("constrain the associated type to `{ident}`"),
where_bound_predicate_to_string(&new_where_bound_predicate),
Applicability::MaybeIncorrect,
);
}
return true;
}
}
}
false
}
/// Check if the source is call expression and the first argument is `self`. If true,
/// return the span of whole call and the span for all arguments expect the first one (`self`).
fn call_has_self_arg(&self, source: PathSource<'_>) -> Option<(Span, Option<Span>)> {
let mut has_self_arg = None;
if let PathSource::Expr(Some(parent)) = source
&& let ExprKind::Call(_, args) = &parent.kind
&& !args.is_empty()
{
let mut expr_kind = &args[0].kind;
loop {
match expr_kind {
ExprKind::Path(_, arg_name) if arg_name.segments.len() == 1 => {
if arg_name.segments[0].ident.name == kw::SelfLower {
let call_span = parent.span;
let tail_args_span = if args.len() > 1 {
Some(Span::new(
args[1].span.lo(),
args.last().unwrap().span.hi(),
call_span.ctxt(),
None,
))
} else {
None
};
has_self_arg = Some((call_span, tail_args_span));
}
break;
}
ExprKind::AddrOf(_, _, expr) => expr_kind = &expr.kind,
_ => break,
}
}
}
has_self_arg
}
fn followed_by_brace(&self, span: Span) -> (bool, Option<Span>) {
// HACK(estebank): find a better way to figure out that this was a
// parser issue where a struct literal is being used on an expression
// where a brace being opened means a block is being started. Look
// ahead for the next text to see if `span` is followed by a `{`.
let sm = self.r.tcx.sess.source_map();
if let Some(followed_brace_span) = sm.span_look_ahead(span, "{", Some(50)) {
// In case this could be a struct literal that needs to be surrounded
// by parentheses, find the appropriate span.
let close_brace_span = sm.span_look_ahead(followed_brace_span, "}", Some(50));
let closing_brace = close_brace_span.map(|sp| span.to(sp));
(true, closing_brace)
} else {
(false, None)
}
}
/// Provides context-dependent help for errors reported by the `smart_resolve_path_fragment`
/// function.
/// Returns `true` if able to provide context-dependent help.
fn smart_resolve_context_dependent_help(
&mut self,
err: &mut Diag<'_>,
span: Span,
source: PathSource<'_>,
path: &[Segment],
res: Res,
path_str: &str,
fallback_label: &str,
) -> bool {
let ns = source.namespace();
let is_expected = &|res| source.is_expected(res);
let path_sep = |this: &mut Self, err: &mut Diag<'_>, expr: &Expr, kind: DefKind| {
const MESSAGE: &str = "use the path separator to refer to an item";
let (lhs_span, rhs_span) = match &expr.kind {
ExprKind::Field(base, ident) => (base.span, ident.span),
ExprKind::MethodCall(box MethodCall { receiver, span, .. }) => {
(receiver.span, *span)
}
_ => return false,
};
if lhs_span.eq_ctxt(rhs_span) {
err.span_suggestion_verbose(
lhs_span.between(rhs_span),
MESSAGE,
"::",
Applicability::MaybeIncorrect,
);
true
} else if matches!(kind, DefKind::Struct | DefKind::TyAlias)
&& let Some(lhs_source_span) = lhs_span.find_ancestor_inside(expr.span)
&& let Ok(snippet) = this.r.tcx.sess.source_map().span_to_snippet(lhs_source_span)
{
// The LHS is a type that originates from a macro call.
// We have to add angle brackets around it.
err.span_suggestion_verbose(
lhs_source_span.until(rhs_span),
MESSAGE,
format!("<{snippet}>::"),
Applicability::MaybeIncorrect,
);
true
} else {
// Either we were unable to obtain the source span / the snippet or
// the LHS originates from a macro call and it is not a type and thus
// there is no way to replace `.` with `::` and still somehow suggest
// valid Rust code.
false
}
};
let find_span = |source: &PathSource<'_>, err: &mut Diag<'_>| {
match source {
PathSource::Expr(Some(Expr { span, kind: ExprKind::Call(_, _), .. }))
| PathSource::TupleStruct(span, _) => {
// We want the main underline to cover the suggested code as well for
// cleaner output.
err.span(*span);
*span
}
_ => span,
}
};
let bad_struct_syntax_suggestion = |this: &mut Self, err: &mut Diag<'_>, def_id: DefId| {
let (followed_by_brace, closing_brace) = this.followed_by_brace(span);
match source {
PathSource::Expr(Some(
parent @ Expr { kind: ExprKind::Field(..) | ExprKind::MethodCall(..), .. },
)) if path_sep(this, err, parent, DefKind::Struct) => {}
PathSource::Expr(
None
| Some(Expr {
kind:
ExprKind::Path(..)
| ExprKind::Binary(..)
| ExprKind::Unary(..)
| ExprKind::If(..)
| ExprKind::While(..)
| ExprKind::ForLoop { .. }
| ExprKind::Match(..),
..
}),
) if followed_by_brace => {
if let Some(sp) = closing_brace {
err.span_label(span, fallback_label.to_string());
err.multipart_suggestion(
"surround the struct literal with parentheses",
vec![
(sp.shrink_to_lo(), "(".to_string()),
(sp.shrink_to_hi(), ")".to_string()),
],
Applicability::MaybeIncorrect,
);
} else {
err.span_label(
span, // Note the parentheses surrounding the suggestion below
format!(
"you might want to surround a struct literal with parentheses: \
`({path_str} {{ /* fields */ }})`?"
),
);
}
}
PathSource::Expr(_) | PathSource::TupleStruct(..) | PathSource::Pat => {
let span = find_span(&source, err);
err.span_label(this.r.def_span(def_id), format!("`{path_str}` defined here"));
let (tail, descr, applicability, old_fields) = match source {
PathSource::Pat => ("", "pattern", Applicability::MachineApplicable, None),
PathSource::TupleStruct(_, args) => (
"",
"pattern",
Applicability::MachineApplicable,
Some(
args.iter()
.map(|a| this.r.tcx.sess.source_map().span_to_snippet(*a).ok())
.collect::<Vec<Option<String>>>(),
),
),
_ => (": val", "literal", Applicability::HasPlaceholders, None),
};
if !this.has_private_fields(def_id) {
// If the fields of the type are private, we shouldn't be suggesting using
// the struct literal syntax at all, as that will cause a subsequent error.
let fields = this.r.field_idents(def_id);
let has_fields = fields.as_ref().is_some_and(|f| !f.is_empty());
let (fields, applicability) = match fields {
Some(fields) => {
let fields = if let Some(old_fields) = old_fields {
fields
.iter()
.enumerate()
.map(|(idx, new)| (new, old_fields.get(idx)))
.map(|(new, old)| {
if let Some(Some(old)) = old
&& new.as_str() != old
{
format!("{new}: {old}")
} else {
new.to_string()
}
})
.collect::<Vec<String>>()
} else {
fields
.iter()
.map(|f| format!("{f}{tail}"))
.collect::<Vec<String>>()
};
(fields.join(", "), applicability)
}
None => ("/* fields */".to_string(), Applicability::HasPlaceholders),
};
let pad = if has_fields { " " } else { "" };
err.span_suggestion(
span,
format!("use struct {descr} syntax instead"),
format!("{path_str} {{{pad}{fields}{pad}}}"),
applicability,
);
}
if let PathSource::Expr(Some(Expr {
kind: ExprKind::Call(path, args),
span: call_span,
..
})) = source
{
this.suggest_alternative_construction_methods(
def_id,
err,
path.span,
*call_span,
&args[..],
);
}
}
_ => {
err.span_label(span, fallback_label.to_string());
}
}
};
match (res, source) {
(
Res::Def(DefKind::Macro(MacroKind::Bang), def_id),
PathSource::Expr(Some(Expr {
kind: ExprKind::Index(..) | ExprKind::Call(..), ..
}))
| PathSource::Struct,
) => {
// Don't suggest macro if it's unstable.
let suggestable = def_id.is_local()
|| self.r.tcx.lookup_stability(def_id).is_none_or(|s| s.is_stable());
err.span_label(span, fallback_label.to_string());
// Don't suggest `!` for a macro invocation if there are generic args
if path
.last()
.is_some_and(|segment| !segment.has_generic_args && !segment.has_lifetime_args)
&& suggestable
{
err.span_suggestion_verbose(
span.shrink_to_hi(),
"use `!` to invoke the macro",
"!",
Applicability::MaybeIncorrect,
);
}
if path_str == "try" && span.is_rust_2015() {
err.note("if you want the `try` keyword, you need Rust 2018 or later");
}
}
(Res::Def(DefKind::Macro(MacroKind::Bang), _), _) => {
err.span_label(span, fallback_label.to_string());
}
(Res::Def(DefKind::TyAlias, def_id), PathSource::Trait(_)) => {
err.span_label(span, "type aliases cannot be used as traits");
if self.r.tcx.sess.is_nightly_build() {
let msg = "you might have meant to use `#![feature(trait_alias)]` instead of a \
`type` alias";
let span = self.r.def_span(def_id);
if let Ok(snip) = self.r.tcx.sess.source_map().span_to_snippet(span) {
// The span contains a type alias so we should be able to
// replace `type` with `trait`.
let snip = snip.replacen("type", "trait", 1);
err.span_suggestion(span, msg, snip, Applicability::MaybeIncorrect);
} else {
err.span_help(span, msg);
}
}
}
(
Res::Def(kind @ (DefKind::Mod | DefKind::Trait | DefKind::TyAlias), _),
PathSource::Expr(Some(parent)),
) if path_sep(self, err, parent, kind) => {
return true;
}
(
Res::Def(DefKind::Enum, def_id),
PathSource::TupleStruct(..) | PathSource::Expr(..),
) => {
self.suggest_using_enum_variant(err, source, def_id, span);
}
(Res::Def(DefKind::Struct, def_id), source) if ns == ValueNS => {
let struct_ctor = match def_id.as_local() {
Some(def_id) => self.r.struct_constructors.get(&def_id).cloned(),
None => {
let ctor = self.r.cstore().ctor_untracked(def_id);
ctor.map(|(ctor_kind, ctor_def_id)| {
let ctor_res =
Res::Def(DefKind::Ctor(CtorOf::Struct, ctor_kind), ctor_def_id);
let ctor_vis = self.r.tcx.visibility(ctor_def_id);
let field_visibilities = self
.r
.tcx
.associated_item_def_ids(def_id)
.iter()
.map(|field_id| self.r.tcx.visibility(field_id))
.collect();
(ctor_res, ctor_vis, field_visibilities)
})
}
};
let (ctor_def, ctor_vis, fields) = if let Some(struct_ctor) = struct_ctor {
if let PathSource::Expr(Some(parent)) = source {
if let ExprKind::Field(..) | ExprKind::MethodCall(..) = parent.kind {
bad_struct_syntax_suggestion(self, err, def_id);
return true;
}
}
struct_ctor
} else {
bad_struct_syntax_suggestion(self, err, def_id);
return true;
};
let is_accessible = self.r.is_accessible_from(ctor_vis, self.parent_scope.module);
if !is_expected(ctor_def) || is_accessible {
return true;
}
let field_spans = match source {
// e.g. `if let Enum::TupleVariant(field1, field2) = _`
PathSource::TupleStruct(_, pattern_spans) => {
err.primary_message(
"cannot match against a tuple struct which contains private fields",
);
// Use spans of the tuple struct pattern.
Some(Vec::from(pattern_spans))
}
// e.g. `let _ = Enum::TupleVariant(field1, field2);`
PathSource::Expr(Some(Expr {
kind: ExprKind::Call(path, args),
span: call_span,
..
})) => {
err.primary_message(
"cannot initialize a tuple struct which contains private fields",
);
self.suggest_alternative_construction_methods(
def_id,
err,
path.span,
*call_span,
&args[..],
);
// Use spans of the tuple struct definition.
self.r
.field_idents(def_id)
.map(|fields| fields.iter().map(|f| f.span).collect::<Vec<_>>())
}
_ => None,
};
if let Some(spans) =
field_spans.filter(|spans| spans.len() > 0 && fields.len() == spans.len())
{
let non_visible_spans: Vec<Span> = iter::zip(&fields, &spans)
.filter(|(vis, _)| {
!self.r.is_accessible_from(**vis, self.parent_scope.module)
})
.map(|(_, span)| *span)
.collect();
if non_visible_spans.len() > 0 {
if let Some(fields) = self.r.field_visibility_spans.get(&def_id) {
err.multipart_suggestion_verbose(
format!(
"consider making the field{} publicly accessible",
pluralize!(fields.len())
),
fields.iter().map(|span| (*span, "pub ".to_string())).collect(),
Applicability::MaybeIncorrect,
);
}
let mut m: MultiSpan = non_visible_spans.clone().into();
non_visible_spans
.into_iter()
.for_each(|s| m.push_span_label(s, "private field"));
err.span_note(m, "constructor is not visible here due to private fields");
}
return true;
}
err.span_label(span, "constructor is not visible here due to private fields");
}
(Res::Def(DefKind::Union | DefKind::Variant, def_id), _) if ns == ValueNS => {
bad_struct_syntax_suggestion(self, err, def_id);
}
(Res::Def(DefKind::Ctor(_, CtorKind::Const), def_id), _) if ns == ValueNS => {
match source {
PathSource::Expr(_) | PathSource::TupleStruct(..) | PathSource::Pat => {
let span = find_span(&source, err);
err.span_label(
self.r.def_span(def_id),
format!("`{path_str}` defined here"),
);
err.span_suggestion(
span,
"use this syntax instead",
path_str,
Applicability::MaybeIncorrect,
);
}
_ => return false,
}
}
(Res::Def(DefKind::Ctor(_, CtorKind::Fn), ctor_def_id), _) if ns == ValueNS => {
let def_id = self.r.tcx.parent(ctor_def_id);
err.span_label(self.r.def_span(def_id), format!("`{path_str}` defined here"));
let fields = self.r.field_idents(def_id).map_or_else(
|| "/* fields */".to_string(),
|field_ids| vec!["_"; field_ids.len()].join(", "),
);
err.span_suggestion(
span,
"use the tuple variant pattern syntax instead",
format!("{path_str}({fields})"),
Applicability::HasPlaceholders,
);
}
(Res::SelfTyParam { .. } | Res::SelfTyAlias { .. }, _) if ns == ValueNS => {
err.span_label(span, fallback_label.to_string());
err.note("can't use `Self` as a constructor, you must use the implemented struct");
}
(Res::Def(DefKind::TyAlias | DefKind::AssocTy, _), _) if ns == ValueNS => {
err.note("can't use a type alias as a constructor");
}
_ => return false,
}
true
}
fn suggest_alternative_construction_methods(
&mut self,
def_id: DefId,
err: &mut Diag<'_>,
path_span: Span,
call_span: Span,
args: &[P<Expr>],
) {
if def_id.is_local() {
// Doing analysis on local `DefId`s would cause infinite recursion.
return;
}
// Look at all the associated functions without receivers in the type's
// inherent impls to look for builders that return `Self`
let mut items = self
.r
.tcx
.inherent_impls(def_id)
.iter()
.flat_map(|i| self.r.tcx.associated_items(i).in_definition_order())
// Only assoc fn with no receivers.
.filter(|item| matches!(item.kind, ty::AssocKind::Fn) && !item.fn_has_self_parameter)
.filter_map(|item| {
// Only assoc fns that return `Self`
let fn_sig = self.r.tcx.fn_sig(item.def_id).skip_binder();
// Don't normalize the return type, because that can cause cycle errors.
let ret_ty = fn_sig.output().skip_binder();
let ty::Adt(def, _args) = ret_ty.kind() else {
return None;
};
let input_len = fn_sig.inputs().skip_binder().len();
if def.did() != def_id {
return None;
}
let order = !item.name.as_str().starts_with("new");
Some((order, item.name, input_len))
})
.collect::<Vec<_>>();
items.sort_by_key(|(order, _, _)| *order);
let suggestion = |name, args| {
format!(
"::{name}({})",
std::iter::repeat("_").take(args).collect::<Vec<_>>().join(", ")
)
};
match &items[..] {
[] => {}
[(_, name, len)] if *len == args.len() => {
err.span_suggestion_verbose(
path_span.shrink_to_hi(),
format!("you might have meant to use the `{name}` associated function",),
format!("::{name}"),
Applicability::MaybeIncorrect,
);
}
[(_, name, len)] => {
err.span_suggestion_verbose(
path_span.shrink_to_hi().with_hi(call_span.hi()),
format!("you might have meant to use the `{name}` associated function",),
suggestion(name, *len),
Applicability::MaybeIncorrect,
);
}
_ => {
err.span_suggestions_with_style(
path_span.shrink_to_hi().with_hi(call_span.hi()),
"you might have meant to use an associated function to build this type",
items.iter().map(|(_, name, len)| suggestion(name, *len)),
Applicability::MaybeIncorrect,
SuggestionStyle::ShowAlways,
);
}
}
// We'd ideally use `type_implements_trait` but don't have access to
// the trait solver here. We can't use `get_diagnostic_item` or
// `all_traits` in resolve either. So instead we abuse the import
// suggestion machinery to get `std::default::Default` and perform some
// checks to confirm that we got *only* that trait. We then see if the
// Adt we have has a direct implementation of `Default`. If so, we
// provide a structured suggestion.
let default_trait = self
.r
.lookup_import_candidates(
Ident::with_dummy_span(sym::Default),
Namespace::TypeNS,
&self.parent_scope,
&|res: Res| matches!(res, Res::Def(DefKind::Trait, _)),
)
.iter()
.filter_map(|candidate| candidate.did)
.find(|did| {
self.r
.tcx
.get_attrs(*did, sym::rustc_diagnostic_item)
.any(|attr| attr.value_str() == Some(sym::Default))
});
let Some(default_trait) = default_trait else {
return;
};
if self
.r
.extern_crate_map
.items()
// FIXME: This doesn't include impls like `impl Default for String`.
.flat_map(|(_, crate_)| self.r.tcx.implementations_of_trait((*crate_, default_trait)))
.filter_map(|(_, simplified_self_ty)| *simplified_self_ty)
.filter_map(|simplified_self_ty| match simplified_self_ty {
SimplifiedType::Adt(did) => Some(did),
_ => None,
})
.any(|did| did == def_id)
{
err.multipart_suggestion(
"consider using the `Default` trait",
vec![
(path_span.shrink_to_lo(), "<".to_string()),
(
path_span.shrink_to_hi().with_hi(call_span.hi()),
" as std::default::Default>::default()".to_string(),
),
],
Applicability::MaybeIncorrect,
);
}
}
fn has_private_fields(&self, def_id: DefId) -> bool {
let fields = match def_id.as_local() {
Some(def_id) => self.r.struct_constructors.get(&def_id).cloned().map(|(_, _, f)| f),
None => Some(
self.r
.tcx
.associated_item_def_ids(def_id)
.iter()
.map(|field_id| self.r.tcx.visibility(field_id))
.collect(),
),
};
fields.is_some_and(|fields| {
fields.iter().any(|vis| !self.r.is_accessible_from(*vis, self.parent_scope.module))
})
}
/// Given the target `ident` and `kind`, search for the similarly named associated item
/// in `self.current_trait_ref`.
pub(crate) fn find_similarly_named_assoc_item(
&mut self,
ident: Symbol,
kind: &AssocItemKind,
) -> Option<Symbol> {
let (module, _) = self.current_trait_ref.as_ref()?;
if ident == kw::Underscore {
// We do nothing for `_`.
return None;
}
let resolutions = self.r.resolutions(*module);
let targets = resolutions
.borrow()
.iter()
.filter_map(|(key, res)| res.borrow().binding.map(|binding| (key, binding.res())))
.filter(|(_, res)| match (kind, res) {
(AssocItemKind::Const(..), Res::Def(DefKind::AssocConst, _)) => true,
(AssocItemKind::Fn(_), Res::Def(DefKind::AssocFn, _)) => true,
(AssocItemKind::Type(..), Res::Def(DefKind::AssocTy, _)) => true,
(AssocItemKind::Delegation(_), Res::Def(DefKind::AssocFn, _)) => true,
_ => false,
})
.map(|(key, _)| key.ident.name)
.collect::<Vec<_>>();
find_best_match_for_name(&targets, ident, None)
}
fn lookup_assoc_candidate<FilterFn>(
&mut self,
ident: Ident,
ns: Namespace,
filter_fn: FilterFn,
called: bool,
) -> Option<AssocSuggestion>
where
FilterFn: Fn(Res) -> bool,
{
fn extract_node_id(t: &Ty) -> Option<NodeId> {
match t.kind {
TyKind::Path(None, _) => Some(t.id),
TyKind::Ref(_, ref mut_ty) => extract_node_id(&mut_ty.ty),
// This doesn't handle the remaining `Ty` variants as they are not
// that commonly the self_type, it might be interesting to provide
// support for those in future.
_ => None,
}
}
// Fields are generally expected in the same contexts as locals.
if filter_fn(Res::Local(ast::DUMMY_NODE_ID)) {
if let Some(node_id) =
self.diag_metadata.current_self_type.as_ref().and_then(extract_node_id)
{
// Look for a field with the same name in the current self_type.
if let Some(resolution) = self.r.partial_res_map.get(&node_id) {
if let Some(Res::Def(DefKind::Struct | DefKind::Union, did)) =
resolution.full_res()
{
if let Some(fields) = self.r.field_idents(did) {
if let Some(field) = fields.iter().find(|id| ident.name == id.name) {
return Some(AssocSuggestion::Field(field.span));
}
}
}
}
}
}
if let Some(items) = self.diag_metadata.current_trait_assoc_items {
for assoc_item in items {
if assoc_item.ident == ident {
return Some(match &assoc_item.kind {
ast::AssocItemKind::Const(..) => AssocSuggestion::AssocConst,
ast::AssocItemKind::Fn(box ast::Fn { sig, .. }) if sig.decl.has_self() => {
AssocSuggestion::MethodWithSelf { called }
}
ast::AssocItemKind::Fn(..) => AssocSuggestion::AssocFn { called },
ast::AssocItemKind::Type(..) => AssocSuggestion::AssocType,
ast::AssocItemKind::Delegation(..)
if self
.r
.delegation_fn_sigs
.get(&self.r.local_def_id(assoc_item.id))
.is_some_and(|sig| sig.has_self) =>
{
AssocSuggestion::MethodWithSelf { called }
}
ast::AssocItemKind::Delegation(..) => AssocSuggestion::AssocFn { called },
ast::AssocItemKind::MacCall(_) | ast::AssocItemKind::DelegationMac(..) => {
continue;
}
});
}
}
}
// Look for associated items in the current trait.
if let Some((module, _)) = self.current_trait_ref {
if let Ok(binding) = self.r.maybe_resolve_ident_in_module(
ModuleOrUniformRoot::Module(module),
ident,
ns,
&self.parent_scope,
None,
) {
let res = binding.res();
if filter_fn(res) {
match res {
Res::Def(DefKind::Fn | DefKind::AssocFn, def_id) => {
let has_self = match def_id.as_local() {
Some(def_id) => self
.r
.delegation_fn_sigs
.get(&def_id)
.is_some_and(|sig| sig.has_self),
None => {
self.r.tcx.fn_arg_names(def_id).first().is_some_and(|&ident| {
matches!(ident, Some(Ident { name: kw::SelfLower, .. }))
})
}
};
if has_self {
return Some(AssocSuggestion::MethodWithSelf { called });
} else {
return Some(AssocSuggestion::AssocFn { called });
}
}
Res::Def(DefKind::AssocConst, _) => {
return Some(AssocSuggestion::AssocConst);
}
Res::Def(DefKind::AssocTy, _) => {
return Some(AssocSuggestion::AssocType);
}
_ => {}
}
}
}
}
None
}
fn lookup_typo_candidate(
&mut self,
path: &[Segment],
following_seg: Option<&Segment>,
ns: Namespace,
filter_fn: &impl Fn(Res) -> bool,
) -> TypoCandidate {
let mut names = Vec::new();
if let [segment] = path {
let mut ctxt = segment.ident.span.ctxt();
// Search in lexical scope.
// Walk backwards up the ribs in scope and collect candidates.
for rib in self.ribs[ns].iter().rev() {
let rib_ctxt = if rib.kind.contains_params() {
ctxt.normalize_to_macros_2_0()
} else {
ctxt.normalize_to_macro_rules()
};
// Locals and type parameters
for (ident, &res) in &rib.bindings {
if filter_fn(res) && ident.span.ctxt() == rib_ctxt {
names.push(TypoSuggestion::typo_from_ident(*ident, res));
}
}
if let RibKind::MacroDefinition(def) = rib.kind
&& def == self.r.macro_def(ctxt)
{
// If an invocation of this macro created `ident`, give up on `ident`
// and switch to `ident`'s source from the macro definition.
ctxt.remove_mark();
continue;
}
// Items in scope
if let RibKind::Module(module) = rib.kind {
// Items from this module
self.r.add_module_candidates(module, &mut names, &filter_fn, Some(ctxt));
if let ModuleKind::Block = module.kind {
// We can see through blocks
} else {
// Items from the prelude
if !module.no_implicit_prelude {
let extern_prelude = self.r.extern_prelude.clone();
names.extend(extern_prelude.iter().flat_map(|(ident, _)| {
self.r
.crate_loader(|c| c.maybe_process_path_extern(ident.name))
.and_then(|crate_id| {
let crate_mod =
Res::Def(DefKind::Mod, crate_id.as_def_id());
filter_fn(crate_mod).then(|| {
TypoSuggestion::typo_from_ident(*ident, crate_mod)
})
})
}));
if let Some(prelude) = self.r.prelude {
self.r.add_module_candidates(prelude, &mut names, &filter_fn, None);
}
}
break;
}
}
}
// Add primitive types to the mix
if filter_fn(Res::PrimTy(PrimTy::Bool)) {
names.extend(PrimTy::ALL.iter().map(|prim_ty| {
TypoSuggestion::typo_from_name(prim_ty.name(), Res::PrimTy(*prim_ty))
}))
}
} else {
// Search in module.
let mod_path = &path[..path.len() - 1];
if let PathResult::Module(ModuleOrUniformRoot::Module(module)) =
self.resolve_path(mod_path, Some(TypeNS), None)
{
self.r.add_module_candidates(module, &mut names, &filter_fn, None);
}
}
// if next_seg is present, let's filter everything that does not continue the path
if let Some(following_seg) = following_seg {
names.retain(|suggestion| match suggestion.res {
Res::Def(DefKind::Struct | DefKind::Enum | DefKind::Union, _) => {
// FIXME: this is not totally accurate, but mostly works
suggestion.candidate != following_seg.ident.name
}
Res::Def(DefKind::Mod, def_id) => self.r.get_module(def_id).map_or_else(
|| false,
|module| {
self.r
.resolutions(module)
.borrow()
.iter()
.any(|(key, _)| key.ident.name == following_seg.ident.name)
},
),
_ => true,
});
}
let name = path[path.len() - 1].ident.name;
// Make sure error reporting is deterministic.
names.sort_by(|a, b| a.candidate.as_str().cmp(b.candidate.as_str()));
match find_best_match_for_name(
&names.iter().map(|suggestion| suggestion.candidate).collect::<Vec<Symbol>>(),
name,
None,
) {
Some(found) => {
let Some(sugg) = names.into_iter().find(|suggestion| suggestion.candidate == found)
else {
return TypoCandidate::None;
};
if found == name {
TypoCandidate::Shadowed(sugg.res, sugg.span)
} else {
TypoCandidate::Typo(sugg)
}
}
_ => TypoCandidate::None,
}
}
// Returns the name of the Rust type approximately corresponding to
// a type name in another programming language.
fn likely_rust_type(path: &[Segment]) -> Option<Symbol> {
let name = path[path.len() - 1].ident.as_str();
// Common Java types
Some(match name {
"byte" => sym::u8, // In Java, bytes are signed, but in practice one almost always wants unsigned bytes.
"short" => sym::i16,
"Bool" => sym::bool,
"Boolean" => sym::bool,
"boolean" => sym::bool,
"int" => sym::i32,
"long" => sym::i64,
"float" => sym::f32,
"double" => sym::f64,
_ => return None,
})
}
// try to give a suggestion for this pattern: `name = blah`, which is common in other languages
// suggest `let name = blah` to introduce a new binding
fn let_binding_suggestion(&mut self, err: &mut Diag<'_>, ident_span: Span) -> bool {
if ident_span.from_expansion() {
return false;
}
// only suggest when the code is a assignment without prefix code
if let Some(Expr { kind: ExprKind::Assign(lhs, ..), .. }) = self.diag_metadata.in_assignment
&& let ast::ExprKind::Path(None, ref path) = lhs.kind
&& self.r.tcx.sess.source_map().is_line_before_span_empty(ident_span)
{
let (span, text) = match path.segments.first() {
Some(seg) if let Some(name) = seg.ident.as_str().strip_prefix("let") => {
// a special case for #117894
let name = name.strip_prefix('_').unwrap_or(name);
(ident_span, format!("let {name}"))
}
_ => (ident_span.shrink_to_lo(), "let ".to_string()),
};
err.span_suggestion_verbose(
span,
"you might have meant to introduce a new binding",
text,
Applicability::MaybeIncorrect,
);
return true;
}
// a special case for #133713
// '=' maybe a typo of `:`, which is a type annotation instead of assignment
if err.code == Some(E0423)
&& let Some((let_span, None, Some(val_span))) = self.diag_metadata.current_let_binding
&& val_span.contains(ident_span)
&& val_span.lo() == ident_span.lo()
{
err.span_suggestion_verbose(
let_span.shrink_to_hi().to(val_span.shrink_to_lo()),
"you might have meant to use `:` for type annotation",
": ",
Applicability::MaybeIncorrect,
);
return true;
}
false
}
fn find_module(&mut self, def_id: DefId) -> Option<(Module<'ra>, ImportSuggestion)> {
let mut result = None;
let mut seen_modules = FxHashSet::default();
let root_did = self.r.graph_root.def_id();
let mut worklist = vec![(
self.r.graph_root,
ThinVec::new(),
root_did.is_local() || !self.r.tcx.is_doc_hidden(root_did),
)];
while let Some((in_module, path_segments, doc_visible)) = worklist.pop() {
// abort if the module is already found
if result.is_some() {
break;
}
in_module.for_each_child(self.r, |r, ident, _, name_binding| {
// abort if the module is already found or if name_binding is private external
if result.is_some() || !name_binding.vis.is_visible_locally() {
return;
}
if let Some(module) = name_binding.module() {
// form the path
let mut path_segments = path_segments.clone();
path_segments.push(ast::PathSegment::from_ident(ident));
let module_def_id = module.def_id();
let doc_visible = doc_visible
&& (module_def_id.is_local() || !r.tcx.is_doc_hidden(module_def_id));
if module_def_id == def_id {
let path =
Path { span: name_binding.span, segments: path_segments, tokens: None };
result = Some((
module,
ImportSuggestion {
did: Some(def_id),
descr: "module",
path,
accessible: true,
doc_visible,
note: None,
via_import: false,
},
));
} else {
// add the module to the lookup
if seen_modules.insert(module_def_id) {
worklist.push((module, path_segments, doc_visible));
}
}
}
});
}
result
}
fn collect_enum_ctors(&mut self, def_id: DefId) -> Option<Vec<(Path, DefId, CtorKind)>> {
self.find_module(def_id).map(|(enum_module, enum_import_suggestion)| {
let mut variants = Vec::new();
enum_module.for_each_child(self.r, |_, ident, _, name_binding| {
if let Res::Def(DefKind::Ctor(CtorOf::Variant, kind), def_id) = name_binding.res() {
let mut segms = enum_import_suggestion.path.segments.clone();
segms.push(ast::PathSegment::from_ident(ident));
let path = Path { span: name_binding.span, segments: segms, tokens: None };
variants.push((path, def_id, kind));
}
});
variants
})
}
/// Adds a suggestion for using an enum's variant when an enum is used instead.
fn suggest_using_enum_variant(
&mut self,
err: &mut Diag<'_>,
source: PathSource<'_>,
def_id: DefId,
span: Span,
) {
let Some(variant_ctors) = self.collect_enum_ctors(def_id) else {
err.note("you might have meant to use one of the enum's variants");
return;
};
// If the expression is a field-access or method-call, try to find a variant with the field/method name
// that could have been intended, and suggest replacing the `.` with `::`.
// Otherwise, suggest adding `::VariantName` after the enum;
// and if the expression is call-like, only suggest tuple variants.
let (suggest_path_sep_dot_span, suggest_only_tuple_variants) = match source {
// `Type(a, b)` in a pattern, only suggest adding a tuple variant after `Type`.
PathSource::TupleStruct(..) => (None, true),
PathSource::Expr(Some(expr)) => match &expr.kind {
// `Type(a, b)`, only suggest adding a tuple variant after `Type`.
ExprKind::Call(..) => (None, true),
// `Type.Foo(a, b)`, suggest replacing `.` -> `::` if variant `Foo` exists and is a tuple variant,
// otherwise suggest adding a variant after `Type`.
ExprKind::MethodCall(box MethodCall {
receiver,
span,
seg: PathSegment { ident, .. },
..
}) => {
let dot_span = receiver.span.between(*span);
let found_tuple_variant = variant_ctors.iter().any(|(path, _, ctor_kind)| {
*ctor_kind == CtorKind::Fn
&& path.segments.last().is_some_and(|seg| seg.ident == *ident)
});
(found_tuple_variant.then_some(dot_span), false)
}
// `Type.Foo`, suggest replacing `.` -> `::` if variant `Foo` exists and is a unit or tuple variant,
// otherwise suggest adding a variant after `Type`.
ExprKind::Field(base, ident) => {
let dot_span = base.span.between(ident.span);
let found_tuple_or_unit_variant = variant_ctors.iter().any(|(path, ..)| {
path.segments.last().is_some_and(|seg| seg.ident == *ident)
});
(found_tuple_or_unit_variant.then_some(dot_span), false)
}
_ => (None, false),
},
_ => (None, false),
};
if let Some(dot_span) = suggest_path_sep_dot_span {
err.span_suggestion_verbose(
dot_span,
"use the path separator to refer to a variant",
"::",
Applicability::MaybeIncorrect,
);
} else if suggest_only_tuple_variants {
// Suggest only tuple variants regardless of whether they have fields and do not
// suggest path with added parentheses.
let mut suggestable_variants = variant_ctors
.iter()
.filter(|(.., kind)| *kind == CtorKind::Fn)
.map(|(variant, ..)| path_names_to_string(variant))
.collect::<Vec<_>>();
suggestable_variants.sort();
let non_suggestable_variant_count = variant_ctors.len() - suggestable_variants.len();
let source_msg = if matches!(source, PathSource::TupleStruct(..)) {
"to match against"
} else {
"to construct"
};
if !suggestable_variants.is_empty() {
let msg = if non_suggestable_variant_count == 0 && suggestable_variants.len() == 1 {
format!("try {source_msg} the enum's variant")
} else {
format!("try {source_msg} one of the enum's variants")
};
err.span_suggestions(
span,
msg,
suggestable_variants,
Applicability::MaybeIncorrect,
);
}
// If the enum has no tuple variants..
if non_suggestable_variant_count == variant_ctors.len() {
err.help(format!("the enum has no tuple variants {source_msg}"));
}
// If there are also non-tuple variants..
if non_suggestable_variant_count == 1 {
err.help(format!("you might have meant {source_msg} the enum's non-tuple variant"));
} else if non_suggestable_variant_count >= 1 {
err.help(format!(
"you might have meant {source_msg} one of the enum's non-tuple variants"
));
}
} else {
let needs_placeholder = |ctor_def_id: DefId, kind: CtorKind| {
let def_id = self.r.tcx.parent(ctor_def_id);
match kind {
CtorKind::Const => false,
CtorKind::Fn => {
!self.r.field_idents(def_id).is_some_and(|field_ids| field_ids.is_empty())
}
}
};
let mut suggestable_variants = variant_ctors
.iter()
.filter(|(_, def_id, kind)| !needs_placeholder(*def_id, *kind))
.map(|(variant, _, kind)| (path_names_to_string(variant), kind))
.map(|(variant, kind)| match kind {
CtorKind::Const => variant,
CtorKind::Fn => format!("({variant}())"),
})
.collect::<Vec<_>>();
suggestable_variants.sort();
let no_suggestable_variant = suggestable_variants.is_empty();
if !no_suggestable_variant {
let msg = if suggestable_variants.len() == 1 {
"you might have meant to use the following enum variant"
} else {
"you might have meant to use one of the following enum variants"
};
err.span_suggestions(
span,
msg,
suggestable_variants,
Applicability::MaybeIncorrect,
);
}
let mut suggestable_variants_with_placeholders = variant_ctors
.iter()
.filter(|(_, def_id, kind)| needs_placeholder(*def_id, *kind))
.map(|(variant, _, kind)| (path_names_to_string(variant), kind))
.filter_map(|(variant, kind)| match kind {
CtorKind::Fn => Some(format!("({variant}(/* fields */))")),
_ => None,
})
.collect::<Vec<_>>();
suggestable_variants_with_placeholders.sort();
if !suggestable_variants_with_placeholders.is_empty() {
let msg =
match (no_suggestable_variant, suggestable_variants_with_placeholders.len()) {
(true, 1) => "the following enum variant is available",
(true, _) => "the following enum variants are available",
(false, 1) => "alternatively, the following enum variant is available",
(false, _) => {
"alternatively, the following enum variants are also available"
}
};
err.span_suggestions(
span,
msg,
suggestable_variants_with_placeholders,
Applicability::HasPlaceholders,
);
}
};
if def_id.is_local() {
err.span_note(self.r.def_span(def_id), "the enum is defined here");
}
}
pub(crate) fn suggest_adding_generic_parameter(
&self,
path: &[Segment],
source: PathSource<'_>,
) -> Option<(Span, &'static str, String, Applicability)> {
let (ident, span) = match path {
[segment]
if !segment.has_generic_args
&& segment.ident.name != kw::SelfUpper
&& segment.ident.name != kw::Dyn =>
{
(segment.ident.to_string(), segment.ident.span)
}
_ => return None,
};
let mut iter = ident.chars().map(|c| c.is_uppercase());
let single_uppercase_char =
matches!(iter.next(), Some(true)) && matches!(iter.next(), None);
if !self.diag_metadata.currently_processing_generic_args && !single_uppercase_char {
return None;
}
match (self.diag_metadata.current_item, single_uppercase_char, self.diag_metadata.currently_processing_generic_args) {
(Some(Item { kind: ItemKind::Fn(..), ident, .. }), _, _) if ident.name == sym::main => {
// Ignore `fn main()` as we don't want to suggest `fn main<T>()`
}
(
Some(Item {
kind:
kind @ ItemKind::Fn(..)
| kind @ ItemKind::Enum(..)
| kind @ ItemKind::Struct(..)
| kind @ ItemKind::Union(..),
..
}),
true, _
)
// Without the 2nd `true`, we'd suggest `impl <T>` for `impl T` when a type `T` isn't found
| (Some(Item { kind: kind @ ItemKind::Impl(..), .. }), true, true)
| (Some(Item { kind, .. }), false, _) => {
if let Some(generics) = kind.generics() {
if span.overlaps(generics.span) {
// Avoid the following:
// error[E0405]: cannot find trait `A` in this scope
// --> $DIR/typo-suggestion-named-underscore.rs:CC:LL
// |
// L | fn foo<T: A>(x: T) {} // Shouldn't suggest underscore
// | ^- help: you might be missing a type parameter: `, A`
// | |
// | not found in this scope
return None;
}
let (msg, sugg) = match source {
PathSource::Type | PathSource::PreciseCapturingArg(TypeNS) => {
("you might be missing a type parameter", ident)
}
PathSource::Expr(_) | PathSource::PreciseCapturingArg(ValueNS) => (
"you might be missing a const parameter",
format!("const {ident}: /* Type */"),
),
_ => return None,
};
let (span, sugg) = if let [.., param] = &generics.params[..] {
let span = if let [.., bound] = &param.bounds[..] {
bound.span()
} else if let GenericParam {
kind: GenericParamKind::Const { ty, kw_span: _, default }, ..
} = param {
default.as_ref().map(|def| def.value.span).unwrap_or(ty.span)
} else {
param.ident.span
};
(span, format!(", {sugg}"))
} else {
(generics.span, format!("<{sugg}>"))
};
// Do not suggest if this is coming from macro expansion.
if span.can_be_used_for_suggestions() {
return Some((
span.shrink_to_hi(),
msg,
sugg,
Applicability::MaybeIncorrect,
));
}
}
}
_ => {}
}
None
}
/// Given the target `label`, search the `rib_index`th label rib for similarly named labels,
/// optionally returning the closest match and whether it is reachable.
pub(crate) fn suggestion_for_label_in_rib(
&self,
rib_index: usize,
label: Ident,
) -> Option<LabelSuggestion> {
// Are ribs from this `rib_index` within scope?
let within_scope = self.is_label_valid_from_rib(rib_index);
let rib = &self.label_ribs[rib_index];
let names = rib
.bindings
.iter()
.filter(|(id, _)| id.span.eq_ctxt(label.span))
.map(|(id, _)| id.name)
.collect::<Vec<Symbol>>();
find_best_match_for_name(&names, label.name, None).map(|symbol| {
// Upon finding a similar name, get the ident that it was from - the span
// contained within helps make a useful diagnostic. In addition, determine
// whether this candidate is within scope.
let (ident, _) = rib.bindings.iter().find(|(ident, _)| ident.name == symbol).unwrap();
(*ident, within_scope)
})
}
pub(crate) fn maybe_report_lifetime_uses(
&mut self,
generics_span: Span,
params: &[ast::GenericParam],
) {
for (param_index, param) in params.iter().enumerate() {
let GenericParamKind::Lifetime = param.kind else { continue };
let def_id = self.r.local_def_id(param.id);
let use_set = self.lifetime_uses.remove(&def_id);
debug!(
"Use set for {:?}({:?} at {:?}) is {:?}",
def_id, param.ident, param.ident.span, use_set
);
let deletion_span = || {
if params.len() == 1 {
// if sole lifetime, remove the entire `<>` brackets
Some(generics_span)
} else if param_index == 0 {
// if removing within `<>` brackets, we also want to
// delete a leading or trailing comma as appropriate
match (
param.span().find_ancestor_inside(generics_span),
params[param_index + 1].span().find_ancestor_inside(generics_span),
) {
(Some(param_span), Some(next_param_span)) => {
Some(param_span.to(next_param_span.shrink_to_lo()))
}
_ => None,
}
} else {
// if removing within `<>` brackets, we also want to
// delete a leading or trailing comma as appropriate
match (
param.span().find_ancestor_inside(generics_span),
params[param_index - 1].span().find_ancestor_inside(generics_span),
) {
(Some(param_span), Some(prev_param_span)) => {
Some(prev_param_span.shrink_to_hi().to(param_span))
}
_ => None,
}
}
};
match use_set {
Some(LifetimeUseSet::Many) => {}
Some(LifetimeUseSet::One { use_span, use_ctxt }) => {
debug!(?param.ident, ?param.ident.span, ?use_span);
let elidable = matches!(use_ctxt, LifetimeCtxt::Ref);
let deletion_span =
if param.bounds.is_empty() { deletion_span() } else { None };
self.r.lint_buffer.buffer_lint(
lint::builtin::SINGLE_USE_LIFETIMES,
param.id,
param.ident.span,
lint::BuiltinLintDiag::SingleUseLifetime {
param_span: param.ident.span,
use_span: Some((use_span, elidable)),
deletion_span,
ident: param.ident,
},
);
}
None => {
debug!(?param.ident, ?param.ident.span);
let deletion_span = deletion_span();
// if the lifetime originates from expanded code, we won't be able to remove it #104432
if deletion_span.is_some_and(|sp| !sp.in_derive_expansion()) {
self.r.lint_buffer.buffer_lint(
lint::builtin::UNUSED_LIFETIMES,
param.id,
param.ident.span,
lint::BuiltinLintDiag::SingleUseLifetime {
param_span: param.ident.span,
use_span: None,
deletion_span,
ident: param.ident,
},
);
}
}
}
}
}
pub(crate) fn emit_undeclared_lifetime_error(
&self,
lifetime_ref: &ast::Lifetime,
outer_lifetime_ref: Option<Ident>,
) {
debug_assert_ne!(lifetime_ref.ident.name, kw::UnderscoreLifetime);
let mut err = if let Some(outer) = outer_lifetime_ref {
struct_span_code_err!(
self.r.dcx(),
lifetime_ref.ident.span,
E0401,
"can't use generic parameters from outer item",
)
.with_span_label(lifetime_ref.ident.span, "use of generic parameter from outer item")
.with_span_label(outer.span, "lifetime parameter from outer item")
} else {
struct_span_code_err!(
self.r.dcx(),
lifetime_ref.ident.span,
E0261,
"use of undeclared lifetime name `{}`",
lifetime_ref.ident
)
.with_span_label(lifetime_ref.ident.span, "undeclared lifetime")
};
// Check if this is a typo of `'static`.
if edit_distance(lifetime_ref.ident.name.as_str(), "'static", 2).is_some() {
err.span_suggestion_verbose(
lifetime_ref.ident.span,
"you may have misspelled the `'static` lifetime",
"'static",
Applicability::MachineApplicable,
);
} else {
self.suggest_introducing_lifetime(
&mut err,
Some(lifetime_ref.ident.name.as_str()),
|err, _, span, message, suggestion, span_suggs| {
err.multipart_suggestion_with_style(
message,
std::iter::once((span, suggestion)).chain(span_suggs.clone()).collect(),
Applicability::MaybeIncorrect,
if span_suggs.is_empty() {
SuggestionStyle::ShowCode
} else {
SuggestionStyle::ShowAlways
},
);
true
},
);
}
err.emit();
}
fn suggest_introducing_lifetime(
&self,
err: &mut Diag<'_>,
name: Option<&str>,
suggest: impl Fn(
&mut Diag<'_>,
bool,
Span,
Cow<'static, str>,
String,
Vec<(Span, String)>,
) -> bool,
) {
let mut suggest_note = true;
for rib in self.lifetime_ribs.iter().rev() {
let mut should_continue = true;
match rib.kind {
LifetimeRibKind::Generics { binder, span, kind } => {
// Avoid suggesting placing lifetime parameters on constant items unless the relevant
// feature is enabled. Suggest the parent item as a possible location if applicable.
if let LifetimeBinderKind::ConstItem = kind
&& !self.r.tcx().features().generic_const_items()
{
continue;
}
if !span.can_be_used_for_suggestions()
&& suggest_note
&& let Some(name) = name
{
suggest_note = false; // Avoid displaying the same help multiple times.
err.span_label(
span,
format!(
"lifetime `{name}` is missing in item created through this procedural macro",
),
);
continue;
}
let higher_ranked = matches!(
kind,
LifetimeBinderKind::BareFnType
| LifetimeBinderKind::PolyTrait
| LifetimeBinderKind::WhereBound
);
let mut rm_inner_binders: FxIndexSet<Span> = Default::default();
let (span, sugg) = if span.is_empty() {
let mut binder_idents: FxIndexSet<Ident> = Default::default();
binder_idents.insert(Ident::from_str(name.unwrap_or("'a")));
// We need to special case binders in the following situation:
// Change `T: for<'a> Trait<T> + 'b` to `for<'a, 'b> T: Trait<T> + 'b`
// T: for<'a> Trait<T> + 'b
// ^^^^^^^ remove existing inner binder `for<'a>`
// for<'a, 'b> T: Trait<T> + 'b
// ^^^^^^^^^^^ suggest outer binder `for<'a, 'b>`
if let LifetimeBinderKind::WhereBound = kind
&& let Some(predicate) = self.diag_metadata.current_where_predicate
&& let ast::WherePredicateKind::BoundPredicate(
ast::WhereBoundPredicate { bounded_ty, bounds, .. },
) = &predicate.kind
&& bounded_ty.id == binder
{
for bound in bounds {
if let ast::GenericBound::Trait(poly_trait_ref) = bound
&& let span = poly_trait_ref
.span
.with_hi(poly_trait_ref.trait_ref.path.span.lo())
&& !span.is_empty()
{
rm_inner_binders.insert(span);
poly_trait_ref.bound_generic_params.iter().for_each(|v| {
binder_idents.insert(v.ident);
});
}
}
}
let binders_sugg = binder_idents.into_iter().enumerate().fold(
"".to_string(),
|mut binders, (i, x)| {
if i != 0 {
binders += ", ";
}
binders += x.as_str();
binders
},
);
let sugg = format!(
"{}<{}>{}",
if higher_ranked { "for" } else { "" },
binders_sugg,
if higher_ranked { " " } else { "" },
);
(span, sugg)
} else {
let span = self
.r
.tcx
.sess
.source_map()
.span_through_char(span, '<')
.shrink_to_hi();
let sugg = format!("{}, ", name.unwrap_or("'a"));
(span, sugg)
};
if higher_ranked {
let message = Cow::from(format!(
"consider making the {} lifetime-generic with a new `{}` lifetime",
kind.descr(),
name.unwrap_or("'a"),
));
should_continue = suggest(
err,
true,
span,
message,
sugg,
if !rm_inner_binders.is_empty() {
rm_inner_binders
.into_iter()
.map(|v| (v, "".to_string()))
.collect::<Vec<_>>()
} else {
vec![]
},
);
err.note_once(
"for more information on higher-ranked polymorphism, visit \
https://doc.rust-lang.org/nomicon/hrtb.html",
);
} else if let Some(name) = name {
let message =
Cow::from(format!("consider introducing lifetime `{name}` here"));
should_continue = suggest(err, false, span, message, sugg, vec![]);
} else {
let message = Cow::from("consider introducing a named lifetime parameter");
should_continue = suggest(err, false, span, message, sugg, vec![]);
}
}
LifetimeRibKind::Item | LifetimeRibKind::ConstParamTy => break,
_ => {}
}
if !should_continue {
break;
}
}
}
pub(crate) fn emit_non_static_lt_in_const_param_ty_error(&self, lifetime_ref: &ast::Lifetime) {
self.r
.dcx()
.create_err(errors::ParamInTyOfConstParam {
span: lifetime_ref.ident.span,
name: lifetime_ref.ident.name,
})
.emit();
}
/// Non-static lifetimes are prohibited in anonymous constants under `min_const_generics`.
/// This function will emit an error if `generic_const_exprs` is not enabled, the body identified by
/// `body_id` is an anonymous constant and `lifetime_ref` is non-static.
pub(crate) fn emit_forbidden_non_static_lifetime_error(
&self,
cause: NoConstantGenericsReason,
lifetime_ref: &ast::Lifetime,
) {
match cause {
NoConstantGenericsReason::IsEnumDiscriminant => {
self.r
.dcx()
.create_err(errors::ParamInEnumDiscriminant {
span: lifetime_ref.ident.span,
name: lifetime_ref.ident.name,
param_kind: errors::ParamKindInEnumDiscriminant::Lifetime,
})
.emit();
}
NoConstantGenericsReason::NonTrivialConstArg => {
assert!(!self.r.tcx.features().generic_const_exprs());
self.r
.dcx()
.create_err(errors::ParamInNonTrivialAnonConst {
span: lifetime_ref.ident.span,
name: lifetime_ref.ident.name,
param_kind: errors::ParamKindInNonTrivialAnonConst::Lifetime,
help: self
.r
.tcx
.sess
.is_nightly_build()
.then_some(errors::ParamInNonTrivialAnonConstHelp),
})
.emit();
}
}
}
pub(crate) fn report_missing_lifetime_specifiers(
&mut self,
lifetime_refs: Vec<MissingLifetime>,
function_param_lifetimes: Option<(Vec<MissingLifetime>, Vec<ElisionFnParameter>)>,
) -> ErrorGuaranteed {
let num_lifetimes: usize = lifetime_refs.iter().map(|lt| lt.count).sum();
let spans: Vec<_> = lifetime_refs.iter().map(|lt| lt.span).collect();
let mut err = struct_span_code_err!(
self.r.dcx(),
spans,
E0106,
"missing lifetime specifier{}",
pluralize!(num_lifetimes)
);
self.add_missing_lifetime_specifiers_label(
&mut err,
lifetime_refs,
function_param_lifetimes,
);
err.emit()
}
fn add_missing_lifetime_specifiers_label(
&mut self,
err: &mut Diag<'_>,
lifetime_refs: Vec<MissingLifetime>,
function_param_lifetimes: Option<(Vec<MissingLifetime>, Vec<ElisionFnParameter>)>,
) {
for &lt in &lifetime_refs {
err.span_label(
lt.span,
format!(
"expected {} lifetime parameter{}",
if lt.count == 1 { "named".to_string() } else { lt.count.to_string() },
pluralize!(lt.count),
),
);
}
let mut in_scope_lifetimes: Vec<_> = self
.lifetime_ribs
.iter()
.rev()
.take_while(|rib| {
!matches!(rib.kind, LifetimeRibKind::Item | LifetimeRibKind::ConstParamTy)
})
.flat_map(|rib| rib.bindings.iter())
.map(|(&ident, &res)| (ident, res))
.filter(|(ident, _)| ident.name != kw::UnderscoreLifetime)
.collect();
debug!(?in_scope_lifetimes);
let mut maybe_static = false;
debug!(?function_param_lifetimes);
if let Some((param_lifetimes, params)) = &function_param_lifetimes {
let elided_len = param_lifetimes.len();
let num_params = params.len();
let mut m = String::new();
for (i, info) in params.iter().enumerate() {
let ElisionFnParameter { ident, index, lifetime_count, span } = *info;
debug_assert_ne!(lifetime_count, 0);
err.span_label(span, "");
if i != 0 {
if i + 1 < num_params {
m.push_str(", ");
} else if num_params == 2 {
m.push_str(" or ");
} else {
m.push_str(", or ");
}
}
let help_name = if let Some(ident) = ident {
format!("`{ident}`")
} else {
format!("argument {}", index + 1)
};
if lifetime_count == 1 {
m.push_str(&help_name[..])
} else {
m.push_str(&format!("one of {help_name}'s {lifetime_count} lifetimes")[..])
}
}
if num_params == 0 {
err.help(
"this function's return type contains a borrowed value, but there is no value \
for it to be borrowed from",
);
if in_scope_lifetimes.is_empty() {
maybe_static = true;
in_scope_lifetimes = vec![(
Ident::with_dummy_span(kw::StaticLifetime),
(DUMMY_NODE_ID, LifetimeRes::Static { suppress_elision_warning: false }),
)];
}
} else if elided_len == 0 {
err.help(
"this function's return type contains a borrowed value with an elided \
lifetime, but the lifetime cannot be derived from the arguments",
);
if in_scope_lifetimes.is_empty() {
maybe_static = true;
in_scope_lifetimes = vec![(
Ident::with_dummy_span(kw::StaticLifetime),
(DUMMY_NODE_ID, LifetimeRes::Static { suppress_elision_warning: false }),
)];
}
} else if num_params == 1 {
err.help(format!(
"this function's return type contains a borrowed value, but the signature does \
not say which {m} it is borrowed from",
));
} else {
err.help(format!(
"this function's return type contains a borrowed value, but the signature does \
not say whether it is borrowed from {m}",
));
}
}
#[allow(rustc::symbol_intern_string_literal)]
let existing_name = match &in_scope_lifetimes[..] {
[] => Symbol::intern("'a"),
[(existing, _)] => existing.name,
_ => Symbol::intern("'lifetime"),
};
let mut spans_suggs: Vec<_> = Vec::new();
let build_sugg = |lt: MissingLifetime| match lt.kind {
MissingLifetimeKind::Underscore => {
debug_assert_eq!(lt.count, 1);
(lt.span, existing_name.to_string())
}
MissingLifetimeKind::Ampersand => {
debug_assert_eq!(lt.count, 1);
(lt.span.shrink_to_hi(), format!("{existing_name} "))
}
MissingLifetimeKind::Comma => {
let sugg: String = std::iter::repeat([existing_name.as_str(), ", "])
.take(lt.count)
.flatten()
.collect();
(lt.span.shrink_to_hi(), sugg)
}
MissingLifetimeKind::Brackets => {
let sugg: String = std::iter::once("<")
.chain(
std::iter::repeat(existing_name.as_str()).take(lt.count).intersperse(", "),
)
.chain([">"])
.collect();
(lt.span.shrink_to_hi(), sugg)
}
};
for &lt in &lifetime_refs {
spans_suggs.push(build_sugg(lt));
}
debug!(?spans_suggs);
match in_scope_lifetimes.len() {
0 => {
if let Some((param_lifetimes, _)) = function_param_lifetimes {
for lt in param_lifetimes {
spans_suggs.push(build_sugg(lt))
}
}
self.suggest_introducing_lifetime(
err,
None,
|err, higher_ranked, span, message, intro_sugg, _| {
err.multipart_suggestion_verbose(
message,
std::iter::once((span, intro_sugg))
.chain(spans_suggs.clone())
.collect(),
Applicability::MaybeIncorrect,
);
higher_ranked
},
);
}
1 => {
let post = if maybe_static {
let owned = if let [lt] = &lifetime_refs[..]
&& lt.kind != MissingLifetimeKind::Ampersand
{
", or if you will only have owned values"
} else {
""
};
format!(
", but this is uncommon unless you're returning a borrowed value from a \
`const` or a `static`{owned}",
)
} else {
String::new()
};
err.multipart_suggestion_verbose(
format!("consider using the `{existing_name}` lifetime{post}"),
spans_suggs,
Applicability::MaybeIncorrect,
);
if maybe_static {
// FIXME: what follows are general suggestions, but we'd want to perform some
// minimal flow analysis to provide more accurate suggestions. For example, if
// we identified that the return expression references only one argument, we
// would suggest borrowing only that argument, and we'd skip the prior
// "use `'static`" suggestion entirely.
if let [lt] = &lifetime_refs[..]
&& (lt.kind == MissingLifetimeKind::Ampersand
|| lt.kind == MissingLifetimeKind::Underscore)
{
let pre = if lt.kind == MissingLifetimeKind::Ampersand
&& let Some((kind, _span)) = self.diag_metadata.current_function
&& let FnKind::Fn(_, _, _, ast::Fn { sig, .. }) = kind
&& !sig.decl.inputs.is_empty()
&& let sugg = sig
.decl
.inputs
.iter()
.filter_map(|param| {
if param.ty.span.contains(lt.span) {
// We don't want to suggest `fn elision(_: &fn() -> &i32)`
// when we have `fn elision(_: fn() -> &i32)`
None
} else if let TyKind::CVarArgs = param.ty.kind {
// Don't suggest `&...` for ffi fn with varargs
None
} else if let TyKind::ImplTrait(..) = &param.ty.kind {
// We handle these in the next `else if` branch.
None
} else {
Some((param.ty.span.shrink_to_lo(), "&".to_string()))
}
})
.collect::<Vec<_>>()
&& !sugg.is_empty()
{
let (the, s) = if sig.decl.inputs.len() == 1 {
("the", "")
} else {
("one of the", "s")
};
err.multipart_suggestion_verbose(
format!(
"instead, you are more likely to want to change {the} \
argument{s} to be borrowed...",
),
sugg,
Applicability::MaybeIncorrect,
);
"...or alternatively, you might want"
} else if (lt.kind == MissingLifetimeKind::Ampersand
|| lt.kind == MissingLifetimeKind::Underscore)
&& let Some((kind, _span)) = self.diag_metadata.current_function
&& let FnKind::Fn(_, _, _, ast::Fn { sig, .. }) = kind
&& let ast::FnRetTy::Ty(ret_ty) = &sig.decl.output
&& !sig.decl.inputs.is_empty()
&& let arg_refs = sig
.decl
.inputs
.iter()
.filter_map(|param| match &param.ty.kind {
TyKind::ImplTrait(_, bounds) => Some(bounds),
_ => None,
})
.flat_map(|bounds| bounds.into_iter())
.collect::<Vec<_>>()
&& !arg_refs.is_empty()
{
// We have a situation like
// fn g(mut x: impl Iterator<Item = &()>) -> Option<&()>
// So we look at every ref in the trait bound. If there's any, we
// suggest
// fn g<'a>(mut x: impl Iterator<Item = &'a ()>) -> Option<&'a ()>
let mut lt_finder =
LifetimeFinder { lifetime: lt.span, found: None, seen: vec![] };
for bound in arg_refs {
if let ast::GenericBound::Trait(trait_ref) = bound {
lt_finder.visit_trait_ref(&trait_ref.trait_ref);
}
}
lt_finder.visit_ty(ret_ty);
let spans_suggs: Vec<_> = lt_finder
.seen
.iter()
.filter_map(|ty| match &ty.kind {
TyKind::Ref(_, mut_ty) => {
let span = ty.span.with_hi(mut_ty.ty.span.lo());
Some((span, "&'a ".to_string()))
}
_ => None,
})
.collect();
self.suggest_introducing_lifetime(
err,
None,
|err, higher_ranked, span, message, intro_sugg, _| {
err.multipart_suggestion_verbose(
message,
std::iter::once((span, intro_sugg))
.chain(spans_suggs.clone())
.collect(),
Applicability::MaybeIncorrect,
);
higher_ranked
},
);
"alternatively, you might want"
} else {
"instead, you are more likely to want"
};
let mut owned_sugg = lt.kind == MissingLifetimeKind::Ampersand;
let mut sugg = vec![(lt.span, String::new())];
if let Some((kind, _span)) = self.diag_metadata.current_function
&& let FnKind::Fn(_, _, _, ast::Fn { sig, .. }) = kind
&& let ast::FnRetTy::Ty(ty) = &sig.decl.output
{
let mut lt_finder =
LifetimeFinder { lifetime: lt.span, found: None, seen: vec![] };
lt_finder.visit_ty(&ty);
if let [Ty { span, kind: TyKind::Ref(_, mut_ty), .. }] =
&lt_finder.seen[..]
{
// We might have a situation like
// fn g(mut x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()>
// but `lt.span` only points at `'_`, so to suggest `-> Option<()>`
// we need to find a more accurate span to end up with
// fn g<'a>(mut x: impl Iterator<Item = &'_ ()>) -> Option<()>
sugg = vec![(span.with_hi(mut_ty.ty.span.lo()), String::new())];
owned_sugg = true;
}
if let Some(ty) = lt_finder.found {
if let TyKind::Path(None, path) = &ty.kind {
// Check if the path being borrowed is likely to be owned.
let path: Vec<_> = Segment::from_path(path);
match self.resolve_path(&path, Some(TypeNS), None) {
PathResult::Module(ModuleOrUniformRoot::Module(module)) => {
match module.res() {
Some(Res::PrimTy(PrimTy::Str)) => {
// Don't suggest `-> str`, suggest `-> String`.
sugg = vec![(
lt.span.with_hi(ty.span.hi()),
"String".to_string(),
)];
}
Some(Res::PrimTy(..)) => {}
Some(Res::Def(
DefKind::Struct
| DefKind::Union
| DefKind::Enum
| DefKind::ForeignTy
| DefKind::AssocTy
| DefKind::OpaqueTy
| DefKind::TyParam,
_,
)) => {}
_ => {
// Do not suggest in all other cases.
owned_sugg = false;
}
}
}
PathResult::NonModule(res) => {
match res.base_res() {
Res::PrimTy(PrimTy::Str) => {
// Don't suggest `-> str`, suggest `-> String`.
sugg = vec![(
lt.span.with_hi(ty.span.hi()),
"String".to_string(),
)];
}
Res::PrimTy(..) => {}
Res::Def(
DefKind::Struct
| DefKind::Union
| DefKind::Enum
| DefKind::ForeignTy
| DefKind::AssocTy
| DefKind::OpaqueTy
| DefKind::TyParam,
_,
) => {}
_ => {
// Do not suggest in all other cases.
owned_sugg = false;
}
}
}
_ => {
// Do not suggest in all other cases.
owned_sugg = false;
}
}
}
if let TyKind::Slice(inner_ty) = &ty.kind {
// Don't suggest `-> [T]`, suggest `-> Vec<T>`.
sugg = vec![
(lt.span.with_hi(inner_ty.span.lo()), "Vec<".to_string()),
(ty.span.with_lo(inner_ty.span.hi()), ">".to_string()),
];
}
}
}
if owned_sugg {
err.multipart_suggestion_verbose(
format!("{pre} to return an owned value"),
sugg,
Applicability::MaybeIncorrect,
);
}
}
}
}
_ => {
let lifetime_spans: Vec<_> =
in_scope_lifetimes.iter().map(|(ident, _)| ident.span).collect();
err.span_note(lifetime_spans, "these named lifetimes are available to use");
if spans_suggs.len() > 0 {
// This happens when we have `Foo<T>` where we point at the space before `T`,
// but this can be confusing so we give a suggestion with placeholders.
err.multipart_suggestion_verbose(
"consider using one of the available lifetimes here",
spans_suggs,
Applicability::HasPlaceholders,
);
}
}
}
}
}
fn mk_where_bound_predicate(
path: &Path,
poly_trait_ref: &ast::PolyTraitRef,
ty: &Ty,
) -> Option<ast::WhereBoundPredicate> {
let modified_segments = {
let mut segments = path.segments.clone();
let [preceding @ .., second_last, last] = segments.as_mut_slice() else {
return None;
};
let mut segments = ThinVec::from(preceding);
let added_constraint = ast::AngleBracketedArg::Constraint(ast::AssocItemConstraint {
id: DUMMY_NODE_ID,
ident: last.ident,
gen_args: None,
kind: ast::AssocItemConstraintKind::Equality {
term: ast::Term::Ty(ast::ptr::P(ast::Ty {
kind: ast::TyKind::Path(None, poly_trait_ref.trait_ref.path.clone()),
id: DUMMY_NODE_ID,
span: DUMMY_SP,
tokens: None,
})),
},
span: DUMMY_SP,
});
match second_last.args.as_deref_mut() {
Some(ast::GenericArgs::AngleBracketed(ast::AngleBracketedArgs { args, .. })) => {
args.push(added_constraint);
}
Some(_) => return None,
None => {
second_last.args =
Some(ast::ptr::P(ast::GenericArgs::AngleBracketed(ast::AngleBracketedArgs {
args: ThinVec::from([added_constraint]),
span: DUMMY_SP,
})));
}
}
segments.push(second_last.clone());
segments
};
let new_where_bound_predicate = ast::WhereBoundPredicate {
bound_generic_params: ThinVec::new(),
bounded_ty: ast::ptr::P(ty.clone()),
bounds: vec![ast::GenericBound::Trait(ast::PolyTraitRef {
bound_generic_params: ThinVec::new(),
modifiers: ast::TraitBoundModifiers::NONE,
trait_ref: ast::TraitRef {
path: ast::Path { segments: modified_segments, span: DUMMY_SP, tokens: None },
ref_id: DUMMY_NODE_ID,
},
span: DUMMY_SP,
})],
};
Some(new_where_bound_predicate)
}
/// Report lifetime/lifetime shadowing as an error.
pub(super) fn signal_lifetime_shadowing(sess: &Session, orig: Ident, shadower: Ident) {
struct_span_code_err!(
sess.dcx(),
shadower.span,
E0496,
"lifetime name `{}` shadows a lifetime name that is already in scope",
orig.name,
)
.with_span_label(orig.span, "first declared here")
.with_span_label(shadower.span, format!("lifetime `{}` already in scope", orig.name))
.emit();
}
struct LifetimeFinder<'ast> {
lifetime: Span,
found: Option<&'ast Ty>,
seen: Vec<&'ast Ty>,
}
impl<'ast> Visitor<'ast> for LifetimeFinder<'ast> {
fn visit_ty(&mut self, t: &'ast Ty) {
if let TyKind::Ref(_, mut_ty) | TyKind::PinnedRef(_, mut_ty) = &t.kind {
self.seen.push(t);
if t.span.lo() == self.lifetime.lo() {
self.found = Some(&mut_ty.ty);
}
}
walk_ty(self, t)
}
}
/// Shadowing involving a label is only a warning for historical reasons.
//FIXME: make this a proper lint.
pub(super) fn signal_label_shadowing(sess: &Session, orig: Span, shadower: Ident) {
let name = shadower.name;
let shadower = shadower.span;
sess.dcx()
.struct_span_warn(
shadower,
format!("label name `{name}` shadows a label name that is already in scope"),
)
.with_span_label(orig, "first declared here")
.with_span_label(shadower, format!("label `{name}` already in scope"))
.emit();
}