| //! Various diagnostics for expressions that are collected together in one pass |
| //! through the body using inference results: mismatched arg counts, missing |
| //! fields, etc. |
| |
| use std::fmt; |
| |
| use base_db::Crate; |
| use either::Either; |
| use hir_def::{ |
| AdtId, AssocItemId, DefWithBodyId, HasModule, ItemContainerId, Lookup, |
| lang_item::LangItem, |
| resolver::{HasResolver, ValueNs}, |
| }; |
| use intern::sym; |
| use itertools::Itertools; |
| use rustc_hash::FxHashSet; |
| use rustc_pattern_analysis::constructor::Constructor; |
| use syntax::{ |
| AstNode, |
| ast::{self, UnaryOp}, |
| }; |
| use tracing::debug; |
| use triomphe::Arc; |
| use typed_arena::Arena; |
| |
| use crate::{ |
| Adjust, InferenceResult, Interner, TraitEnvironment, Ty, TyExt, TyKind, |
| db::HirDatabase, |
| diagnostics::match_check::{ |
| self, |
| pat_analysis::{self, DeconstructedPat, MatchCheckCtx, WitnessPat}, |
| }, |
| display::{DisplayTarget, HirDisplay}, |
| }; |
| |
| pub(crate) use hir_def::{ |
| LocalFieldId, VariantId, |
| expr_store::Body, |
| hir::{Expr, ExprId, MatchArm, Pat, PatId, Statement}, |
| }; |
| |
| pub enum BodyValidationDiagnostic { |
| RecordMissingFields { |
| record: Either<ExprId, PatId>, |
| variant: VariantId, |
| missed_fields: Vec<LocalFieldId>, |
| }, |
| ReplaceFilterMapNextWithFindMap { |
| method_call_expr: ExprId, |
| }, |
| MissingMatchArms { |
| match_expr: ExprId, |
| uncovered_patterns: String, |
| }, |
| NonExhaustiveLet { |
| pat: PatId, |
| uncovered_patterns: String, |
| }, |
| RemoveTrailingReturn { |
| return_expr: ExprId, |
| }, |
| RemoveUnnecessaryElse { |
| if_expr: ExprId, |
| }, |
| } |
| |
| impl BodyValidationDiagnostic { |
| pub fn collect( |
| db: &dyn HirDatabase, |
| owner: DefWithBodyId, |
| validate_lints: bool, |
| ) -> Vec<BodyValidationDiagnostic> { |
| let _p = tracing::info_span!("BodyValidationDiagnostic::collect").entered(); |
| let infer = db.infer(owner); |
| let body = db.body(owner); |
| let env = db.trait_environment_for_body(owner); |
| let mut validator = |
| ExprValidator { owner, body, infer, diagnostics: Vec::new(), validate_lints, env }; |
| validator.validate_body(db); |
| validator.diagnostics |
| } |
| } |
| |
| struct ExprValidator<'db> { |
| owner: DefWithBodyId, |
| body: Arc<Body>, |
| infer: Arc<InferenceResult>, |
| env: Arc<TraitEnvironment<'db>>, |
| diagnostics: Vec<BodyValidationDiagnostic>, |
| validate_lints: bool, |
| } |
| |
| impl<'db> ExprValidator<'db> { |
| fn validate_body(&mut self, db: &'db dyn HirDatabase) { |
| let mut filter_map_next_checker = None; |
| // we'll pass &mut self while iterating over body.exprs, so they need to be disjoint |
| let body = Arc::clone(&self.body); |
| |
| if matches!(self.owner, DefWithBodyId::FunctionId(_)) { |
| self.check_for_trailing_return(body.body_expr, &body); |
| } |
| |
| for (id, expr) in body.exprs() { |
| if let Some((variant, missed_fields, true)) = |
| record_literal_missing_fields(db, &self.infer, id, expr) |
| { |
| self.diagnostics.push(BodyValidationDiagnostic::RecordMissingFields { |
| record: Either::Left(id), |
| variant, |
| missed_fields, |
| }); |
| } |
| |
| match expr { |
| Expr::Match { expr, arms } => { |
| self.validate_match(id, *expr, arms, db); |
| } |
| Expr::Call { .. } | Expr::MethodCall { .. } => { |
| self.validate_call(db, id, expr, &mut filter_map_next_checker); |
| } |
| Expr::Closure { body: body_expr, .. } => { |
| self.check_for_trailing_return(*body_expr, &body); |
| } |
| Expr::If { .. } => { |
| self.check_for_unnecessary_else(id, expr, db); |
| } |
| Expr::Block { .. } | Expr::Async { .. } | Expr::Unsafe { .. } => { |
| self.validate_block(db, expr); |
| } |
| _ => {} |
| } |
| } |
| |
| for (id, pat) in body.pats() { |
| if let Some((variant, missed_fields, true)) = |
| record_pattern_missing_fields(db, &self.infer, id, pat) |
| { |
| self.diagnostics.push(BodyValidationDiagnostic::RecordMissingFields { |
| record: Either::Right(id), |
| variant, |
| missed_fields, |
| }); |
| } |
| } |
| } |
| |
| fn validate_call( |
| &mut self, |
| db: &dyn HirDatabase, |
| call_id: ExprId, |
| expr: &Expr, |
| filter_map_next_checker: &mut Option<FilterMapNextChecker>, |
| ) { |
| if !self.validate_lints { |
| return; |
| } |
| // Check that the number of arguments matches the number of parameters. |
| |
| if self.infer.expr_type_mismatches().next().is_some() { |
| // FIXME: Due to shortcomings in the current type system implementation, only emit |
| // this diagnostic if there are no type mismatches in the containing function. |
| } else if let Expr::MethodCall { receiver, .. } = expr { |
| let (callee, _) = match self.infer.method_resolution(call_id) { |
| Some(it) => it, |
| None => return, |
| }; |
| |
| let checker = filter_map_next_checker |
| .get_or_insert_with(|| FilterMapNextChecker::new(&self.owner.resolver(db), db)); |
| |
| if checker.check(call_id, receiver, &callee).is_some() { |
| self.diagnostics.push(BodyValidationDiagnostic::ReplaceFilterMapNextWithFindMap { |
| method_call_expr: call_id, |
| }); |
| } |
| |
| if let Some(receiver_ty) = self.infer.type_of_expr_with_adjust(*receiver) { |
| checker.prev_receiver_ty = Some(receiver_ty.clone()); |
| } |
| } |
| } |
| |
| fn validate_match( |
| &mut self, |
| match_expr: ExprId, |
| scrutinee_expr: ExprId, |
| arms: &[MatchArm], |
| db: &dyn HirDatabase, |
| ) { |
| let Some(scrut_ty) = self.infer.type_of_expr_with_adjust(scrutinee_expr) else { |
| return; |
| }; |
| if scrut_ty.contains_unknown() { |
| return; |
| } |
| |
| let cx = MatchCheckCtx::new(self.owner.module(db), self.owner, db, self.env.clone()); |
| |
| let pattern_arena = Arena::new(); |
| let mut m_arms = Vec::with_capacity(arms.len()); |
| let mut has_lowering_errors = false; |
| // Note: Skipping the entire diagnostic rather than just not including a faulty match arm is |
| // preferred to avoid the chance of false positives. |
| for arm in arms { |
| let Some(pat_ty) = self.infer.type_of_pat_with_adjust(arm.pat) else { |
| return; |
| }; |
| if pat_ty.contains_unknown() { |
| return; |
| } |
| |
| // We only include patterns whose type matches the type |
| // of the scrutinee expression. If we had an InvalidMatchArmPattern |
| // diagnostic or similar we could raise that in an else |
| // block here. |
| // |
| // When comparing the types, we also have to consider that rustc |
| // will automatically de-reference the scrutinee expression type if |
| // necessary. |
| // |
| // FIXME we should use the type checker for this. |
| if (pat_ty == scrut_ty |
| || scrut_ty |
| .as_reference() |
| .map(|(match_expr_ty, ..)| match_expr_ty == pat_ty) |
| .unwrap_or(false)) |
| && types_of_subpatterns_do_match(arm.pat, &self.body, &self.infer) |
| { |
| // If we had a NotUsefulMatchArm diagnostic, we could |
| // check the usefulness of each pattern as we added it |
| // to the matrix here. |
| let pat = self.lower_pattern(&cx, arm.pat, db, &mut has_lowering_errors); |
| let m_arm = pat_analysis::MatchArm { |
| pat: pattern_arena.alloc(pat), |
| has_guard: arm.guard.is_some(), |
| arm_data: (), |
| }; |
| m_arms.push(m_arm); |
| if !has_lowering_errors { |
| continue; |
| } |
| } |
| // If the pattern type doesn't fit the match expression, we skip this diagnostic. |
| cov_mark::hit!(validate_match_bailed_out); |
| return; |
| } |
| |
| let known_valid_scrutinee = Some(self.is_known_valid_scrutinee(scrutinee_expr, db)); |
| let report = match cx.compute_match_usefulness( |
| m_arms.as_slice(), |
| scrut_ty.clone(), |
| known_valid_scrutinee, |
| ) { |
| Ok(report) => report, |
| Err(()) => return, |
| }; |
| |
| // FIXME Report unreachable arms |
| // https://github.com/rust-lang/rust/blob/f31622a50/compiler/rustc_mir_build/src/thir/pattern/check_match.rs#L200 |
| |
| let witnesses = report.non_exhaustiveness_witnesses; |
| if !witnesses.is_empty() { |
| self.diagnostics.push(BodyValidationDiagnostic::MissingMatchArms { |
| match_expr, |
| uncovered_patterns: missing_match_arms( |
| &cx, |
| scrut_ty, |
| witnesses, |
| m_arms.is_empty(), |
| self.owner.krate(db), |
| ), |
| }); |
| } |
| } |
| |
| // [rustc's `is_known_valid_scrutinee`](https://github.com/rust-lang/rust/blob/c9bd03cb724e13cca96ad320733046cbdb16fbbe/compiler/rustc_mir_build/src/thir/pattern/check_match.rs#L288) |
| // |
| // While the above function in rustc uses thir exprs, r-a doesn't have them. |
| // So, the logic here is getting same result as "hir lowering + match with lowered thir" |
| // with "hir only" |
| fn is_known_valid_scrutinee(&self, scrutinee_expr: ExprId, db: &dyn HirDatabase) -> bool { |
| if self |
| .infer |
| .expr_adjustments |
| .get(&scrutinee_expr) |
| .is_some_and(|adjusts| adjusts.iter().any(|a| matches!(a.kind, Adjust::Deref(..)))) |
| { |
| return false; |
| } |
| |
| match &self.body[scrutinee_expr] { |
| Expr::UnaryOp { op: UnaryOp::Deref, .. } => false, |
| Expr::Path(path) => { |
| let value_or_partial = self.owner.resolver(db).resolve_path_in_value_ns_fully( |
| db, |
| path, |
| self.body.expr_path_hygiene(scrutinee_expr), |
| ); |
| value_or_partial.is_none_or(|v| !matches!(v, ValueNs::StaticId(_))) |
| } |
| Expr::Field { expr, .. } => match self.infer.type_of_expr[*expr].kind(Interner) { |
| TyKind::Adt(adt, ..) if matches!(adt.0, AdtId::UnionId(_)) => false, |
| _ => self.is_known_valid_scrutinee(*expr, db), |
| }, |
| Expr::Index { base, .. } => self.is_known_valid_scrutinee(*base, db), |
| Expr::Cast { expr, .. } => self.is_known_valid_scrutinee(*expr, db), |
| Expr::Missing => false, |
| _ => true, |
| } |
| } |
| |
| fn validate_block(&mut self, db: &dyn HirDatabase, expr: &Expr) { |
| let (Expr::Block { statements, .. } |
| | Expr::Async { statements, .. } |
| | Expr::Unsafe { statements, .. }) = expr |
| else { |
| return; |
| }; |
| let pattern_arena = Arena::new(); |
| let cx = MatchCheckCtx::new(self.owner.module(db), self.owner, db, self.env.clone()); |
| for stmt in &**statements { |
| let &Statement::Let { pat, initializer, else_branch: None, .. } = stmt else { |
| continue; |
| }; |
| if self.infer.type_mismatch_for_pat(pat).is_some() { |
| continue; |
| } |
| let Some(initializer) = initializer else { continue }; |
| let Some(ty) = self.infer.type_of_expr_with_adjust(initializer) else { continue }; |
| if ty.contains_unknown() { |
| continue; |
| } |
| |
| let mut have_errors = false; |
| let deconstructed_pat = self.lower_pattern(&cx, pat, db, &mut have_errors); |
| |
| // optimization, wildcard trivially hold |
| if have_errors || matches!(deconstructed_pat.ctor(), Constructor::Wildcard) { |
| continue; |
| } |
| |
| let match_arm = rustc_pattern_analysis::MatchArm { |
| pat: pattern_arena.alloc(deconstructed_pat), |
| has_guard: false, |
| arm_data: (), |
| }; |
| let report = match cx.compute_match_usefulness(&[match_arm], ty.clone(), None) { |
| Ok(v) => v, |
| Err(e) => { |
| debug!(?e, "match usefulness error"); |
| continue; |
| } |
| }; |
| let witnesses = report.non_exhaustiveness_witnesses; |
| if !witnesses.is_empty() { |
| self.diagnostics.push(BodyValidationDiagnostic::NonExhaustiveLet { |
| pat, |
| uncovered_patterns: missing_match_arms( |
| &cx, |
| ty, |
| witnesses, |
| false, |
| self.owner.krate(db), |
| ), |
| }); |
| } |
| } |
| } |
| |
| fn lower_pattern<'p>( |
| &self, |
| cx: &MatchCheckCtx<'p>, |
| pat: PatId, |
| db: &dyn HirDatabase, |
| have_errors: &mut bool, |
| ) -> DeconstructedPat<'p> { |
| let mut patcx = match_check::PatCtxt::new(db, &self.infer, &self.body); |
| let pattern = patcx.lower_pattern(pat); |
| let pattern = cx.lower_pat(&pattern); |
| if !patcx.errors.is_empty() { |
| *have_errors = true; |
| } |
| pattern |
| } |
| |
| fn check_for_trailing_return(&mut self, body_expr: ExprId, body: &Body) { |
| if !self.validate_lints { |
| return; |
| } |
| match &body[body_expr] { |
| Expr::Block { statements, tail, .. } => { |
| let last_stmt = tail.or_else(|| match statements.last()? { |
| Statement::Expr { expr, .. } => Some(*expr), |
| _ => None, |
| }); |
| if let Some(last_stmt) = last_stmt { |
| self.check_for_trailing_return(last_stmt, body); |
| } |
| } |
| Expr::If { then_branch, else_branch, .. } => { |
| self.check_for_trailing_return(*then_branch, body); |
| if let Some(else_branch) = else_branch { |
| self.check_for_trailing_return(*else_branch, body); |
| } |
| } |
| Expr::Match { arms, .. } => { |
| for arm in arms.iter() { |
| let MatchArm { expr, .. } = arm; |
| self.check_for_trailing_return(*expr, body); |
| } |
| } |
| Expr::Return { .. } => { |
| self.diagnostics.push(BodyValidationDiagnostic::RemoveTrailingReturn { |
| return_expr: body_expr, |
| }); |
| } |
| _ => (), |
| } |
| } |
| |
| fn check_for_unnecessary_else(&mut self, id: ExprId, expr: &Expr, db: &dyn HirDatabase) { |
| if !self.validate_lints { |
| return; |
| } |
| if let Expr::If { condition: _, then_branch, else_branch } = expr { |
| if else_branch.is_none() { |
| return; |
| } |
| if let Expr::Block { statements, tail, .. } = &self.body[*then_branch] { |
| let last_then_expr = tail.or_else(|| match statements.last()? { |
| Statement::Expr { expr, .. } => Some(*expr), |
| _ => None, |
| }); |
| if let Some(last_then_expr) = last_then_expr |
| && let Some(last_then_expr_ty) = |
| self.infer.type_of_expr_with_adjust(last_then_expr) |
| && last_then_expr_ty.is_never() |
| { |
| // Only look at sources if the then branch diverges and we have an else branch. |
| let source_map = db.body_with_source_map(self.owner).1; |
| let Ok(source_ptr) = source_map.expr_syntax(id) else { |
| return; |
| }; |
| let root = source_ptr.file_syntax(db); |
| let either::Left(ast::Expr::IfExpr(if_expr)) = source_ptr.value.to_node(&root) |
| else { |
| return; |
| }; |
| let mut top_if_expr = if_expr; |
| loop { |
| let parent = top_if_expr.syntax().parent(); |
| let has_parent_expr_stmt_or_stmt_list = |
| parent.as_ref().is_some_and(|node| { |
| ast::ExprStmt::can_cast(node.kind()) |
| | ast::StmtList::can_cast(node.kind()) |
| }); |
| if has_parent_expr_stmt_or_stmt_list { |
| // Only emit diagnostic if parent or direct ancestor is either |
| // an expr stmt or a stmt list. |
| break; |
| } |
| let Some(parent_if_expr) = parent.and_then(ast::IfExpr::cast) else { |
| // Bail if parent is neither an if expr, an expr stmt nor a stmt list. |
| return; |
| }; |
| // Check parent if expr. |
| top_if_expr = parent_if_expr; |
| } |
| |
| self.diagnostics |
| .push(BodyValidationDiagnostic::RemoveUnnecessaryElse { if_expr: id }) |
| } |
| } |
| } |
| } |
| } |
| |
| struct FilterMapNextChecker { |
| filter_map_function_id: Option<hir_def::FunctionId>, |
| next_function_id: Option<hir_def::FunctionId>, |
| prev_filter_map_expr_id: Option<ExprId>, |
| prev_receiver_ty: Option<chalk_ir::Ty<Interner>>, |
| } |
| |
| impl FilterMapNextChecker { |
| fn new(resolver: &hir_def::resolver::Resolver<'_>, db: &dyn HirDatabase) -> Self { |
| // Find and store the FunctionIds for Iterator::filter_map and Iterator::next |
| let (next_function_id, filter_map_function_id) = match LangItem::IteratorNext |
| .resolve_function(db, resolver.krate()) |
| { |
| Some(next_function_id) => ( |
| Some(next_function_id), |
| match next_function_id.lookup(db).container { |
| ItemContainerId::TraitId(iterator_trait_id) => { |
| let iterator_trait_items = &iterator_trait_id.trait_items(db).items; |
| iterator_trait_items.iter().find_map(|(name, it)| match it { |
| &AssocItemId::FunctionId(id) if *name == sym::filter_map => Some(id), |
| _ => None, |
| }) |
| } |
| _ => None, |
| }, |
| ), |
| None => (None, None), |
| }; |
| Self { |
| filter_map_function_id, |
| next_function_id, |
| prev_filter_map_expr_id: None, |
| prev_receiver_ty: None, |
| } |
| } |
| |
| // check for instances of .filter_map(..).next() |
| fn check( |
| &mut self, |
| current_expr_id: ExprId, |
| receiver_expr_id: &ExprId, |
| function_id: &hir_def::FunctionId, |
| ) -> Option<()> { |
| if *function_id == self.filter_map_function_id? { |
| self.prev_filter_map_expr_id = Some(current_expr_id); |
| return None; |
| } |
| |
| if *function_id == self.next_function_id? |
| && let Some(prev_filter_map_expr_id) = self.prev_filter_map_expr_id |
| { |
| let is_dyn_trait = self |
| .prev_receiver_ty |
| .as_ref() |
| .is_some_and(|it| it.strip_references().dyn_trait().is_some()); |
| if *receiver_expr_id == prev_filter_map_expr_id && !is_dyn_trait { |
| return Some(()); |
| } |
| } |
| |
| self.prev_filter_map_expr_id = None; |
| None |
| } |
| } |
| |
| pub fn record_literal_missing_fields( |
| db: &dyn HirDatabase, |
| infer: &InferenceResult, |
| id: ExprId, |
| expr: &Expr, |
| ) -> Option<(VariantId, Vec<LocalFieldId>, /*exhaustive*/ bool)> { |
| let (fields, exhaustive) = match expr { |
| Expr::RecordLit { fields, spread, .. } => (fields, spread.is_none()), |
| _ => return None, |
| }; |
| |
| let variant_def = infer.variant_resolution_for_expr(id)?; |
| if let VariantId::UnionId(_) = variant_def { |
| return None; |
| } |
| |
| let variant_data = variant_def.fields(db); |
| |
| let specified_fields: FxHashSet<_> = fields.iter().map(|f| &f.name).collect(); |
| let missed_fields: Vec<LocalFieldId> = variant_data |
| .fields() |
| .iter() |
| .filter_map(|(f, d)| if specified_fields.contains(&d.name) { None } else { Some(f) }) |
| .collect(); |
| if missed_fields.is_empty() { |
| return None; |
| } |
| Some((variant_def, missed_fields, exhaustive)) |
| } |
| |
| pub fn record_pattern_missing_fields( |
| db: &dyn HirDatabase, |
| infer: &InferenceResult, |
| id: PatId, |
| pat: &Pat, |
| ) -> Option<(VariantId, Vec<LocalFieldId>, /*exhaustive*/ bool)> { |
| let (fields, exhaustive) = match pat { |
| Pat::Record { path: _, args, ellipsis } => (args, !ellipsis), |
| _ => return None, |
| }; |
| |
| let variant_def = infer.variant_resolution_for_pat(id)?; |
| if let VariantId::UnionId(_) = variant_def { |
| return None; |
| } |
| |
| let variant_data = variant_def.fields(db); |
| |
| let specified_fields: FxHashSet<_> = fields.iter().map(|f| &f.name).collect(); |
| let missed_fields: Vec<LocalFieldId> = variant_data |
| .fields() |
| .iter() |
| .filter_map(|(f, d)| if specified_fields.contains(&d.name) { None } else { Some(f) }) |
| .collect(); |
| if missed_fields.is_empty() { |
| return None; |
| } |
| Some((variant_def, missed_fields, exhaustive)) |
| } |
| |
| fn types_of_subpatterns_do_match(pat: PatId, body: &Body, infer: &InferenceResult) -> bool { |
| fn walk(pat: PatId, body: &Body, infer: &InferenceResult, has_type_mismatches: &mut bool) { |
| match infer.type_mismatch_for_pat(pat) { |
| Some(_) => *has_type_mismatches = true, |
| None if *has_type_mismatches => (), |
| None => { |
| let pat = &body[pat]; |
| if let Pat::ConstBlock(expr) | Pat::Lit(expr) = *pat { |
| *has_type_mismatches |= infer.type_mismatch_for_expr(expr).is_some(); |
| if *has_type_mismatches { |
| return; |
| } |
| } |
| pat.walk_child_pats(|subpat| walk(subpat, body, infer, has_type_mismatches)) |
| } |
| } |
| } |
| |
| let mut has_type_mismatches = false; |
| walk(pat, body, infer, &mut has_type_mismatches); |
| !has_type_mismatches |
| } |
| |
| fn missing_match_arms<'p>( |
| cx: &MatchCheckCtx<'p>, |
| scrut_ty: &Ty, |
| witnesses: Vec<WitnessPat<'p>>, |
| arms_is_empty: bool, |
| krate: Crate, |
| ) -> String { |
| struct DisplayWitness<'a, 'p>(&'a WitnessPat<'p>, &'a MatchCheckCtx<'p>, DisplayTarget); |
| impl fmt::Display for DisplayWitness<'_, '_> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| let DisplayWitness(witness, cx, display_target) = *self; |
| let pat = cx.hoist_witness_pat(witness); |
| write!(f, "{}", pat.display(cx.db, display_target)) |
| } |
| } |
| |
| let non_empty_enum = match scrut_ty.as_adt() { |
| Some((AdtId::EnumId(e), _)) => !e.enum_variants(cx.db).variants.is_empty(), |
| _ => false, |
| }; |
| let display_target = DisplayTarget::from_crate(cx.db, krate); |
| if arms_is_empty && !non_empty_enum { |
| format!("type `{}` is non-empty", scrut_ty.display(cx.db, display_target)) |
| } else { |
| let pat_display = |witness| DisplayWitness(witness, cx, display_target); |
| const LIMIT: usize = 3; |
| match &*witnesses { |
| [witness] => format!("`{}` not covered", pat_display(witness)), |
| [head @ .., tail] if head.len() < LIMIT => { |
| let head = head.iter().map(pat_display); |
| format!("`{}` and `{}` not covered", head.format("`, `"), pat_display(tail)) |
| } |
| _ => { |
| let (head, tail) = witnesses.split_at(LIMIT); |
| let head = head.iter().map(pat_display); |
| format!("`{}` and {} more not covered", head.format("`, `"), tail.len()) |
| } |
| } |
| } |
| } |
