| //! A different sort of visitor for walking fn bodies. Unlike the |
| //! normal visitor, which just walks the entire body in one shot, the |
| //! `ExprUseVisitor` determines how expressions are being used. |
| |
| pub use self::LoanCause::*; |
| pub use self::ConsumeMode::*; |
| pub use self::MoveReason::*; |
| pub use self::MatchMode::*; |
| use self::TrackMatchMode::*; |
| use self::OverloadedCallType::*; |
| |
| use crate::hir::def::{CtorOf, Res, DefKind}; |
| use crate::hir::def_id::DefId; |
| use crate::hir::ptr::P; |
| use crate::infer::InferCtxt; |
| use crate::middle::mem_categorization as mc; |
| use crate::middle::region; |
| use crate::ty::{self, DefIdTree, TyCtxt, adjustment}; |
| |
| use crate::hir::{self, PatKind}; |
| use std::rc::Rc; |
| use syntax_pos::Span; |
| use crate::util::nodemap::ItemLocalSet; |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // The Delegate trait |
| |
| /// This trait defines the callbacks you can expect to receive when |
| /// employing the ExprUseVisitor. |
| pub trait Delegate<'tcx> { |
| // The value found at `cmt` is either copied or moved, depending |
| // on mode. |
| fn consume(&mut self, |
| consume_id: hir::HirId, |
| consume_span: Span, |
| cmt: &mc::cmt_<'tcx>, |
| mode: ConsumeMode); |
| |
| // The value found at `cmt` has been determined to match the |
| // pattern binding `matched_pat`, and its subparts are being |
| // copied or moved depending on `mode`. Note that `matched_pat` |
| // is called on all variant/structs in the pattern (i.e., the |
| // interior nodes of the pattern's tree structure) while |
| // consume_pat is called on the binding identifiers in the pattern |
| // (which are leaves of the pattern's tree structure). |
| // |
| // Note that variants/structs and identifiers are disjoint; thus |
| // `matched_pat` and `consume_pat` are never both called on the |
| // same input pattern structure (though of `consume_pat` can be |
| // called on a subpart of an input passed to `matched_pat). |
| fn matched_pat(&mut self, |
| matched_pat: &hir::Pat, |
| cmt: &mc::cmt_<'tcx>, |
| mode: MatchMode); |
| |
| // The value found at `cmt` is either copied or moved via the |
| // pattern binding `consume_pat`, depending on mode. |
| fn consume_pat(&mut self, |
| consume_pat: &hir::Pat, |
| cmt: &mc::cmt_<'tcx>, |
| mode: ConsumeMode); |
| |
| // The value found at `borrow` is being borrowed at the point |
| // `borrow_id` for the region `loan_region` with kind `bk`. |
| fn borrow(&mut self, |
| borrow_id: hir::HirId, |
| borrow_span: Span, |
| cmt: &mc::cmt_<'tcx>, |
| loan_region: ty::Region<'tcx>, |
| bk: ty::BorrowKind, |
| loan_cause: LoanCause); |
| |
| // The local variable `id` is declared but not initialized. |
| fn decl_without_init(&mut self, |
| id: hir::HirId, |
| span: Span); |
| |
| // The path at `cmt` is being assigned to. |
| fn mutate(&mut self, |
| assignment_id: hir::HirId, |
| assignment_span: Span, |
| assignee_cmt: &mc::cmt_<'tcx>, |
| mode: MutateMode); |
| |
| // A nested closure or generator - only one layer deep. |
| fn nested_body(&mut self, _body_id: hir::BodyId) {} |
| } |
| |
| #[derive(Copy, Clone, PartialEq, Debug)] |
| pub enum LoanCause { |
| ClosureCapture(Span), |
| AddrOf, |
| AutoRef, |
| AutoUnsafe, |
| RefBinding, |
| OverloadedOperator, |
| ClosureInvocation, |
| ForLoop, |
| MatchDiscriminant |
| } |
| |
| #[derive(Copy, Clone, PartialEq, Debug)] |
| pub enum ConsumeMode { |
| Copy, // reference to x where x has a type that copies |
| Move(MoveReason), // reference to x where x has a type that moves |
| } |
| |
| #[derive(Copy, Clone, PartialEq, Debug)] |
| pub enum MoveReason { |
| DirectRefMove, |
| PatBindingMove, |
| CaptureMove, |
| } |
| |
| #[derive(Copy, Clone, PartialEq, Debug)] |
| pub enum MatchMode { |
| NonBindingMatch, |
| BorrowingMatch, |
| CopyingMatch, |
| MovingMatch, |
| } |
| |
| #[derive(Copy, Clone, PartialEq, Debug)] |
| enum TrackMatchMode { |
| Unknown, |
| Definite(MatchMode), |
| Conflicting, |
| } |
| |
| impl TrackMatchMode { |
| // Builds up the whole match mode for a pattern from its constituent |
| // parts. The lattice looks like this: |
| // |
| // Conflicting |
| // / \ |
| // / \ |
| // Borrowing Moving |
| // \ / |
| // \ / |
| // Copying |
| // | |
| // NonBinding |
| // | |
| // Unknown |
| // |
| // examples: |
| // |
| // * `(_, some_int)` pattern is Copying, since |
| // NonBinding + Copying => Copying |
| // |
| // * `(some_int, some_box)` pattern is Moving, since |
| // Copying + Moving => Moving |
| // |
| // * `(ref x, some_box)` pattern is Conflicting, since |
| // Borrowing + Moving => Conflicting |
| // |
| // Note that the `Unknown` and `Conflicting` states are |
| // represented separately from the other more interesting |
| // `Definite` states, which simplifies logic here somewhat. |
| fn lub(&mut self, mode: MatchMode) { |
| *self = match (*self, mode) { |
| // Note that clause order below is very significant. |
| (Unknown, new) => Definite(new), |
| (Definite(old), new) if old == new => Definite(old), |
| |
| (Definite(old), NonBindingMatch) => Definite(old), |
| (Definite(NonBindingMatch), new) => Definite(new), |
| |
| (Definite(old), CopyingMatch) => Definite(old), |
| (Definite(CopyingMatch), new) => Definite(new), |
| |
| (Definite(_), _) => Conflicting, |
| (Conflicting, _) => *self, |
| }; |
| } |
| |
| fn match_mode(&self) -> MatchMode { |
| match *self { |
| Unknown => NonBindingMatch, |
| Definite(mode) => mode, |
| Conflicting => { |
| // Conservatively return MovingMatch to let the |
| // compiler continue to make progress. |
| MovingMatch |
| } |
| } |
| } |
| } |
| |
| #[derive(Copy, Clone, PartialEq, Debug)] |
| pub enum MutateMode { |
| Init, |
| JustWrite, // x = y |
| WriteAndRead, // x += y |
| } |
| |
| #[derive(Copy, Clone)] |
| enum OverloadedCallType { |
| FnOverloadedCall, |
| FnMutOverloadedCall, |
| FnOnceOverloadedCall, |
| } |
| |
| impl OverloadedCallType { |
| fn from_trait_id(tcx: TyCtxt<'_>, trait_id: DefId) -> OverloadedCallType { |
| for &(maybe_function_trait, overloaded_call_type) in &[ |
| (tcx.lang_items().fn_once_trait(), FnOnceOverloadedCall), |
| (tcx.lang_items().fn_mut_trait(), FnMutOverloadedCall), |
| (tcx.lang_items().fn_trait(), FnOverloadedCall) |
| ] { |
| match maybe_function_trait { |
| Some(function_trait) if function_trait == trait_id => { |
| return overloaded_call_type |
| } |
| _ => continue, |
| } |
| } |
| |
| bug!("overloaded call didn't map to known function trait") |
| } |
| |
| fn from_method_id(tcx: TyCtxt<'_>, method_id: DefId) -> OverloadedCallType { |
| let method = tcx.associated_item(method_id); |
| OverloadedCallType::from_trait_id(tcx, method.container.id()) |
| } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // The ExprUseVisitor type |
| // |
| // This is the code that actually walks the tree. |
| pub struct ExprUseVisitor<'a, 'tcx> { |
| mc: mc::MemCategorizationContext<'a, 'tcx>, |
| delegate: &'a mut dyn Delegate<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| } |
| |
| // If the MC results in an error, it's because the type check |
| // failed (or will fail, when the error is uncovered and reported |
| // during writeback). In this case, we just ignore this part of the |
| // code. |
| // |
| // Note that this macro appears similar to try!(), but, unlike try!(), |
| // it does not propagate the error. |
| macro_rules! return_if_err { |
| ($inp: expr) => ( |
| match $inp { |
| Ok(v) => v, |
| Err(()) => { |
| debug!("mc reported err"); |
| return |
| } |
| } |
| ) |
| } |
| |
| impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> { |
| /// Creates the ExprUseVisitor, configuring it with the various options provided: |
| /// |
| /// - `delegate` -- who receives the callbacks |
| /// - `param_env` --- parameter environment for trait lookups (esp. pertaining to `Copy`) |
| /// - `region_scope_tree` --- region scope tree for the code being analyzed |
| /// - `tables` --- typeck results for the code being analyzed |
| /// - `rvalue_promotable_map` --- if you care about rvalue promotion, then provide |
| /// the map here (it can be computed with `tcx.rvalue_promotable_map(def_id)`). |
| /// `None` means that rvalues will be given more conservative lifetimes. |
| /// |
| /// See also `with_infer`, which is used *during* typeck. |
| pub fn new( |
| delegate: &'a mut (dyn Delegate<'tcx> + 'a), |
| tcx: TyCtxt<'tcx>, |
| body_owner: DefId, |
| param_env: ty::ParamEnv<'tcx>, |
| region_scope_tree: &'a region::ScopeTree, |
| tables: &'a ty::TypeckTables<'tcx>, |
| rvalue_promotable_map: Option<&'tcx ItemLocalSet>, |
| ) -> Self { |
| ExprUseVisitor { |
| mc: mc::MemCategorizationContext::new(tcx, |
| param_env, |
| body_owner, |
| region_scope_tree, |
| tables, |
| rvalue_promotable_map), |
| delegate, |
| param_env, |
| } |
| } |
| } |
| |
| impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> { |
| pub fn with_infer( |
| delegate: &'a mut (dyn Delegate<'tcx> + 'a), |
| infcx: &'a InferCtxt<'a, 'tcx>, |
| body_owner: DefId, |
| param_env: ty::ParamEnv<'tcx>, |
| region_scope_tree: &'a region::ScopeTree, |
| tables: &'a ty::TypeckTables<'tcx>, |
| ) -> Self { |
| ExprUseVisitor { |
| mc: mc::MemCategorizationContext::with_infer( |
| infcx, |
| param_env, |
| body_owner, |
| region_scope_tree, |
| tables, |
| ), |
| delegate, |
| param_env, |
| } |
| } |
| |
| pub fn consume_body(&mut self, body: &hir::Body) { |
| debug!("consume_body(body={:?})", body); |
| |
| for param in &body.params { |
| let param_ty = return_if_err!(self.mc.pat_ty_adjusted(¶m.pat)); |
| debug!("consume_body: param_ty = {:?}", param_ty); |
| |
| let fn_body_scope_r = |
| self.tcx().mk_region(ty::ReScope( |
| region::Scope { |
| id: body.value.hir_id.local_id, |
| data: region::ScopeData::Node |
| })); |
| let param_cmt = Rc::new(self.mc.cat_rvalue( |
| param.hir_id, |
| param.pat.span, |
| fn_body_scope_r, // Parameters live only as long as the fn body. |
| param_ty)); |
| |
| self.walk_irrefutable_pat(param_cmt, ¶m.pat); |
| } |
| |
| self.consume_expr(&body.value); |
| } |
| |
| fn tcx(&self) -> TyCtxt<'tcx> { |
| self.mc.tcx |
| } |
| |
| fn delegate_consume(&mut self, |
| consume_id: hir::HirId, |
| consume_span: Span, |
| cmt: &mc::cmt_<'tcx>) { |
| debug!("delegate_consume(consume_id={}, cmt={:?})", |
| consume_id, cmt); |
| |
| let mode = copy_or_move(&self.mc, self.param_env, cmt, DirectRefMove); |
| self.delegate.consume(consume_id, consume_span, cmt, mode); |
| } |
| |
| fn consume_exprs(&mut self, exprs: &[hir::Expr]) { |
| for expr in exprs { |
| self.consume_expr(&expr); |
| } |
| } |
| |
| pub fn consume_expr(&mut self, expr: &hir::Expr) { |
| debug!("consume_expr(expr={:?})", expr); |
| |
| let cmt = return_if_err!(self.mc.cat_expr(expr)); |
| self.delegate_consume(expr.hir_id, expr.span, &cmt); |
| self.walk_expr(expr); |
| } |
| |
| fn mutate_expr(&mut self, |
| span: Span, |
| assignment_expr: &hir::Expr, |
| expr: &hir::Expr, |
| mode: MutateMode) { |
| let cmt = return_if_err!(self.mc.cat_expr(expr)); |
| self.delegate.mutate(assignment_expr.hir_id, span, &cmt, mode); |
| self.walk_expr(expr); |
| } |
| |
| fn borrow_expr(&mut self, |
| expr: &hir::Expr, |
| r: ty::Region<'tcx>, |
| bk: ty::BorrowKind, |
| cause: LoanCause) { |
| debug!("borrow_expr(expr={:?}, r={:?}, bk={:?})", |
| expr, r, bk); |
| |
| let cmt = return_if_err!(self.mc.cat_expr(expr)); |
| self.delegate.borrow(expr.hir_id, expr.span, &cmt, r, bk, cause); |
| |
| self.walk_expr(expr) |
| } |
| |
| fn select_from_expr(&mut self, expr: &hir::Expr) { |
| self.walk_expr(expr) |
| } |
| |
| pub fn walk_expr(&mut self, expr: &hir::Expr) { |
| debug!("walk_expr(expr={:?})", expr); |
| |
| self.walk_adjustment(expr); |
| |
| match expr.node { |
| hir::ExprKind::Path(_) => { } |
| |
| hir::ExprKind::Type(ref subexpr, _) => { |
| self.walk_expr(&subexpr) |
| } |
| |
| hir::ExprKind::Unary(hir::UnDeref, ref base) => { // *base |
| self.select_from_expr(&base); |
| } |
| |
| hir::ExprKind::Field(ref base, _) => { // base.f |
| self.select_from_expr(&base); |
| } |
| |
| hir::ExprKind::Index(ref lhs, ref rhs) => { // lhs[rhs] |
| self.select_from_expr(&lhs); |
| self.consume_expr(&rhs); |
| } |
| |
| hir::ExprKind::Call(ref callee, ref args) => { // callee(args) |
| self.walk_callee(expr, &callee); |
| self.consume_exprs(args); |
| } |
| |
| hir::ExprKind::MethodCall(.., ref args) => { // callee.m(args) |
| self.consume_exprs(args); |
| } |
| |
| hir::ExprKind::Struct(_, ref fields, ref opt_with) => { |
| self.walk_struct_expr(fields, opt_with); |
| } |
| |
| hir::ExprKind::Tup(ref exprs) => { |
| self.consume_exprs(exprs); |
| } |
| |
| hir::ExprKind::Match(ref discr, ref arms, _) => { |
| let discr_cmt = Rc::new(return_if_err!(self.mc.cat_expr(&discr))); |
| let r = self.tcx().lifetimes.re_empty; |
| self.borrow_expr(&discr, r, ty::ImmBorrow, MatchDiscriminant); |
| |
| // treatment of the discriminant is handled while walking the arms. |
| for arm in arms { |
| let mode = self.arm_move_mode(discr_cmt.clone(), arm); |
| let mode = mode.match_mode(); |
| self.walk_arm(discr_cmt.clone(), arm, mode); |
| } |
| } |
| |
| hir::ExprKind::Array(ref exprs) => { |
| self.consume_exprs(exprs); |
| } |
| |
| hir::ExprKind::AddrOf(m, ref base) => { // &base |
| // make sure that the thing we are pointing out stays valid |
| // for the lifetime `scope_r` of the resulting ptr: |
| let expr_ty = return_if_err!(self.mc.expr_ty(expr)); |
| if let ty::Ref(r, _, _) = expr_ty.sty { |
| let bk = ty::BorrowKind::from_mutbl(m); |
| self.borrow_expr(&base, r, bk, AddrOf); |
| } |
| } |
| |
| hir::ExprKind::InlineAsm(ref ia, ref outputs, ref inputs) => { |
| for (o, output) in ia.outputs.iter().zip(outputs) { |
| if o.is_indirect { |
| self.consume_expr(output); |
| } else { |
| self.mutate_expr( |
| output.span, |
| expr, |
| output, |
| if o.is_rw { |
| MutateMode::WriteAndRead |
| } else { |
| MutateMode::JustWrite |
| }, |
| ); |
| } |
| } |
| self.consume_exprs(inputs); |
| } |
| |
| hir::ExprKind::Continue(..) | |
| hir::ExprKind::Lit(..) | |
| hir::ExprKind::Err => {} |
| |
| hir::ExprKind::Loop(ref blk, _, _) => { |
| self.walk_block(&blk); |
| } |
| |
| hir::ExprKind::Unary(_, ref lhs) => { |
| self.consume_expr(&lhs); |
| } |
| |
| hir::ExprKind::Binary(_, ref lhs, ref rhs) => { |
| self.consume_expr(&lhs); |
| self.consume_expr(&rhs); |
| } |
| |
| hir::ExprKind::Block(ref blk, _) => { |
| self.walk_block(&blk); |
| } |
| |
| hir::ExprKind::Break(_, ref opt_expr) | hir::ExprKind::Ret(ref opt_expr) => { |
| if let Some(ref expr) = *opt_expr { |
| self.consume_expr(&expr); |
| } |
| } |
| |
| hir::ExprKind::Assign(ref lhs, ref rhs) => { |
| self.mutate_expr(expr.span, expr, &lhs, MutateMode::JustWrite); |
| self.consume_expr(&rhs); |
| } |
| |
| hir::ExprKind::Cast(ref base, _) => { |
| self.consume_expr(&base); |
| } |
| |
| hir::ExprKind::DropTemps(ref expr) => { |
| self.consume_expr(&expr); |
| } |
| |
| hir::ExprKind::AssignOp(_, ref lhs, ref rhs) => { |
| if self.mc.tables.is_method_call(expr) { |
| self.consume_expr(lhs); |
| } else { |
| self.mutate_expr(expr.span, expr, &lhs, MutateMode::WriteAndRead); |
| } |
| self.consume_expr(&rhs); |
| } |
| |
| hir::ExprKind::Repeat(ref base, _) => { |
| self.consume_expr(&base); |
| } |
| |
| hir::ExprKind::Closure(_, _, body_id, fn_decl_span, _) => { |
| self.delegate.nested_body(body_id); |
| self.walk_captures(expr, fn_decl_span); |
| } |
| |
| hir::ExprKind::Box(ref base) => { |
| self.consume_expr(&base); |
| } |
| |
| hir::ExprKind::Yield(ref value, _) => { |
| self.consume_expr(&value); |
| } |
| } |
| } |
| |
| fn walk_callee(&mut self, call: &hir::Expr, callee: &hir::Expr) { |
| let callee_ty = return_if_err!(self.mc.expr_ty_adjusted(callee)); |
| debug!("walk_callee: callee={:?} callee_ty={:?}", |
| callee, callee_ty); |
| match callee_ty.sty { |
| ty::FnDef(..) | ty::FnPtr(_) => { |
| self.consume_expr(callee); |
| } |
| ty::Error => { } |
| _ => { |
| if let Some(def_id) = self.mc.tables.type_dependent_def_id(call.hir_id) { |
| let call_scope = region::Scope { |
| id: call.hir_id.local_id, |
| data: region::ScopeData::Node |
| }; |
| match OverloadedCallType::from_method_id(self.tcx(), def_id) { |
| FnMutOverloadedCall => { |
| let call_scope_r = self.tcx().mk_region(ty::ReScope(call_scope)); |
| self.borrow_expr(callee, |
| call_scope_r, |
| ty::MutBorrow, |
| ClosureInvocation); |
| } |
| FnOverloadedCall => { |
| let call_scope_r = self.tcx().mk_region(ty::ReScope(call_scope)); |
| self.borrow_expr(callee, |
| call_scope_r, |
| ty::ImmBorrow, |
| ClosureInvocation); |
| } |
| FnOnceOverloadedCall => self.consume_expr(callee), |
| } |
| } else { |
| self.tcx().sess.delay_span_bug(call.span, |
| "no type-dependent def for overloaded call"); |
| } |
| } |
| } |
| } |
| |
| fn walk_stmt(&mut self, stmt: &hir::Stmt) { |
| match stmt.node { |
| hir::StmtKind::Local(ref local) => { |
| self.walk_local(&local); |
| } |
| |
| hir::StmtKind::Item(_) => { |
| // We don't visit nested items in this visitor, |
| // only the fn body we were given. |
| } |
| |
| hir::StmtKind::Expr(ref expr) | |
| hir::StmtKind::Semi(ref expr) => { |
| self.consume_expr(&expr); |
| } |
| } |
| } |
| |
| fn walk_local(&mut self, local: &hir::Local) { |
| match local.init { |
| None => { |
| local.pat.each_binding(|_, hir_id, span, _| { |
| self.delegate.decl_without_init(hir_id, span); |
| }) |
| } |
| |
| Some(ref expr) => { |
| // Variable declarations with |
| // initializers are considered |
| // "assigns", which is handled by |
| // `walk_pat`: |
| self.walk_expr(&expr); |
| let init_cmt = Rc::new(return_if_err!(self.mc.cat_expr(&expr))); |
| self.walk_irrefutable_pat(init_cmt, &local.pat); |
| } |
| } |
| } |
| |
| /// Indicates that the value of `blk` will be consumed, meaning either copied or moved |
| /// depending on its type. |
| fn walk_block(&mut self, blk: &hir::Block) { |
| debug!("walk_block(blk.hir_id={})", blk.hir_id); |
| |
| for stmt in &blk.stmts { |
| self.walk_stmt(stmt); |
| } |
| |
| if let Some(ref tail_expr) = blk.expr { |
| self.consume_expr(&tail_expr); |
| } |
| } |
| |
| fn walk_struct_expr(&mut self, |
| fields: &[hir::Field], |
| opt_with: &Option<P<hir::Expr>>) { |
| // Consume the expressions supplying values for each field. |
| for field in fields { |
| self.consume_expr(&field.expr); |
| } |
| |
| let with_expr = match *opt_with { |
| Some(ref w) => &**w, |
| None => { return; } |
| }; |
| |
| let with_cmt = Rc::new(return_if_err!(self.mc.cat_expr(&with_expr))); |
| |
| // Select just those fields of the `with` |
| // expression that will actually be used |
| match with_cmt.ty.sty { |
| ty::Adt(adt, substs) if adt.is_struct() => { |
| // Consume those fields of the with expression that are needed. |
| for (f_index, with_field) in adt.non_enum_variant().fields.iter().enumerate() { |
| let is_mentioned = fields.iter().any(|f| { |
| self.tcx().field_index(f.hir_id, self.mc.tables) == f_index |
| }); |
| if !is_mentioned { |
| let cmt_field = self.mc.cat_field( |
| &*with_expr, |
| with_cmt.clone(), |
| f_index, |
| with_field.ident, |
| with_field.ty(self.tcx(), substs) |
| ); |
| self.delegate_consume(with_expr.hir_id, with_expr.span, &cmt_field); |
| } |
| } |
| } |
| _ => { |
| // the base expression should always evaluate to a |
| // struct; however, when EUV is run during typeck, it |
| // may not. This will generate an error earlier in typeck, |
| // so we can just ignore it. |
| if !self.tcx().sess.has_errors() { |
| span_bug!( |
| with_expr.span, |
| "with expression doesn't evaluate to a struct"); |
| } |
| } |
| } |
| |
| // walk the with expression so that complex expressions |
| // are properly handled. |
| self.walk_expr(with_expr); |
| } |
| |
| // Invoke the appropriate delegate calls for anything that gets |
| // consumed or borrowed as part of the automatic adjustment |
| // process. |
| fn walk_adjustment(&mut self, expr: &hir::Expr) { |
| let adjustments = self.mc.tables.expr_adjustments(expr); |
| let mut cmt = return_if_err!(self.mc.cat_expr_unadjusted(expr)); |
| for adjustment in adjustments { |
| debug!("walk_adjustment expr={:?} adj={:?}", expr, adjustment); |
| match adjustment.kind { |
| adjustment::Adjust::NeverToAny | |
| adjustment::Adjust::Pointer(_) => { |
| // Creating a closure/fn-pointer or unsizing consumes |
| // the input and stores it into the resulting rvalue. |
| self.delegate_consume(expr.hir_id, expr.span, &cmt); |
| } |
| |
| adjustment::Adjust::Deref(None) => {} |
| |
| // Autoderefs for overloaded Deref calls in fact reference |
| // their receiver. That is, if we have `(*x)` where `x` |
| // is of type `Rc<T>`, then this in fact is equivalent to |
| // `x.deref()`. Since `deref()` is declared with `&self`, |
| // this is an autoref of `x`. |
| adjustment::Adjust::Deref(Some(ref deref)) => { |
| let bk = ty::BorrowKind::from_mutbl(deref.mutbl); |
| self.delegate.borrow(expr.hir_id, expr.span, &cmt, deref.region, bk, AutoRef); |
| } |
| |
| adjustment::Adjust::Borrow(ref autoref) => { |
| self.walk_autoref(expr, &cmt, autoref); |
| } |
| } |
| cmt = return_if_err!(self.mc.cat_expr_adjusted(expr, cmt, &adjustment)); |
| } |
| } |
| |
| /// Walks the autoref `autoref` applied to the autoderef'd |
| /// `expr`. `cmt_base` is the mem-categorized form of `expr` |
| /// after all relevant autoderefs have occurred. |
| fn walk_autoref(&mut self, |
| expr: &hir::Expr, |
| cmt_base: &mc::cmt_<'tcx>, |
| autoref: &adjustment::AutoBorrow<'tcx>) { |
| debug!("walk_autoref(expr.hir_id={} cmt_base={:?} autoref={:?})", |
| expr.hir_id, |
| cmt_base, |
| autoref); |
| |
| match *autoref { |
| adjustment::AutoBorrow::Ref(r, m) => { |
| self.delegate.borrow(expr.hir_id, |
| expr.span, |
| cmt_base, |
| r, |
| ty::BorrowKind::from_mutbl(m.into()), |
| AutoRef); |
| } |
| |
| adjustment::AutoBorrow::RawPtr(m) => { |
| debug!("walk_autoref: expr.hir_id={} cmt_base={:?}", |
| expr.hir_id, |
| cmt_base); |
| |
| // Converting from a &T to *T (or &mut T to *mut T) is |
| // treated as borrowing it for the enclosing temporary |
| // scope. |
| let r = self.tcx().mk_region(ty::ReScope( |
| region::Scope { |
| id: expr.hir_id.local_id, |
| data: region::ScopeData::Node |
| })); |
| |
| self.delegate.borrow(expr.hir_id, |
| expr.span, |
| cmt_base, |
| r, |
| ty::BorrowKind::from_mutbl(m), |
| AutoUnsafe); |
| } |
| } |
| } |
| |
| fn arm_move_mode(&mut self, discr_cmt: mc::cmt<'tcx>, arm: &hir::Arm) -> TrackMatchMode { |
| let mut mode = Unknown; |
| for pat in arm.top_pats_hack() { |
| self.determine_pat_move_mode(discr_cmt.clone(), &pat, &mut mode); |
| } |
| mode |
| } |
| |
| fn walk_arm(&mut self, discr_cmt: mc::cmt<'tcx>, arm: &hir::Arm, mode: MatchMode) { |
| for pat in arm.top_pats_hack() { |
| self.walk_pat(discr_cmt.clone(), &pat, mode); |
| } |
| |
| if let Some(hir::Guard::If(ref e)) = arm.guard { |
| self.consume_expr(e) |
| } |
| |
| self.consume_expr(&arm.body); |
| } |
| |
| /// Walks a pat that occurs in isolation (i.e., top-level of fn argument or |
| /// let binding, and *not* a match arm or nested pat.) |
| fn walk_irrefutable_pat(&mut self, cmt_discr: mc::cmt<'tcx>, pat: &hir::Pat) { |
| let mut mode = Unknown; |
| self.determine_pat_move_mode(cmt_discr.clone(), pat, &mut mode); |
| let mode = mode.match_mode(); |
| self.walk_pat(cmt_discr, pat, mode); |
| } |
| |
| /// Identifies any bindings within `pat` and accumulates within |
| /// `mode` whether the overall pattern/match structure is a move, |
| /// copy, or borrow. |
| fn determine_pat_move_mode(&mut self, |
| cmt_discr: mc::cmt<'tcx>, |
| pat: &hir::Pat, |
| mode: &mut TrackMatchMode) { |
| debug!("determine_pat_move_mode cmt_discr={:?} pat={:?}", cmt_discr, pat); |
| |
| return_if_err!(self.mc.cat_pattern(cmt_discr, pat, |cmt_pat, pat| { |
| if let PatKind::Binding(..) = pat.node { |
| let bm = *self.mc.tables.pat_binding_modes() |
| .get(pat.hir_id) |
| .expect("missing binding mode"); |
| match bm { |
| ty::BindByReference(..) => |
| mode.lub(BorrowingMatch), |
| ty::BindByValue(..) => { |
| match copy_or_move(&self.mc, self.param_env, &cmt_pat, PatBindingMove) { |
| Copy => mode.lub(CopyingMatch), |
| Move(..) => mode.lub(MovingMatch), |
| } |
| } |
| } |
| } |
| })); |
| } |
| |
| /// The core driver for walking a pattern; `match_mode` must be |
| /// established up front, e.g., via `determine_pat_move_mode` (see |
| /// also `walk_irrefutable_pat` for patterns that stand alone). |
| fn walk_pat(&mut self, cmt_discr: mc::cmt<'tcx>, pat: &hir::Pat, match_mode: MatchMode) { |
| debug!("walk_pat(cmt_discr={:?}, pat={:?})", cmt_discr, pat); |
| |
| let tcx = self.tcx(); |
| let ExprUseVisitor { ref mc, ref mut delegate, param_env } = *self; |
| return_if_err!(mc.cat_pattern(cmt_discr.clone(), pat, |cmt_pat, pat| { |
| if let PatKind::Binding(_, canonical_id, ..) = pat.node { |
| debug!( |
| "walk_pat: binding cmt_pat={:?} pat={:?} match_mode={:?}", |
| cmt_pat, |
| pat, |
| match_mode, |
| ); |
| if let Some(&bm) = mc.tables.pat_binding_modes().get(pat.hir_id) { |
| debug!("walk_pat: pat.hir_id={:?} bm={:?}", pat.hir_id, bm); |
| |
| // pat_ty: the type of the binding being produced. |
| let pat_ty = return_if_err!(mc.node_ty(pat.hir_id)); |
| debug!("walk_pat: pat_ty={:?}", pat_ty); |
| |
| // Each match binding is effectively an assignment to the |
| // binding being produced. |
| let def = Res::Local(canonical_id); |
| if let Ok(ref binding_cmt) = mc.cat_res(pat.hir_id, pat.span, pat_ty, def) { |
| delegate.mutate(pat.hir_id, pat.span, binding_cmt, MutateMode::Init); |
| } |
| |
| // It is also a borrow or copy/move of the value being matched. |
| match bm { |
| ty::BindByReference(m) => { |
| if let ty::Ref(r, _, _) = pat_ty.sty { |
| let bk = ty::BorrowKind::from_mutbl(m); |
| delegate.borrow(pat.hir_id, pat.span, &cmt_pat, r, bk, RefBinding); |
| } |
| } |
| ty::BindByValue(..) => { |
| let mode = copy_or_move(mc, param_env, &cmt_pat, PatBindingMove); |
| debug!("walk_pat binding consuming pat"); |
| delegate.consume_pat(pat, &cmt_pat, mode); |
| } |
| } |
| } else { |
| tcx.sess.delay_span_bug(pat.span, "missing binding mode"); |
| } |
| } |
| })); |
| |
| // Do a second pass over the pattern, calling `matched_pat` on |
| // the interior nodes (enum variants and structs), as opposed |
| // to the above loop's visit of than the bindings that form |
| // the leaves of the pattern tree structure. |
| return_if_err!(mc.cat_pattern(cmt_discr, pat, |cmt_pat, pat| { |
| let qpath = match pat.node { |
| PatKind::Path(ref qpath) | |
| PatKind::TupleStruct(ref qpath, ..) | |
| PatKind::Struct(ref qpath, ..) => qpath, |
| _ => return |
| }; |
| let res = mc.tables.qpath_res(qpath, pat.hir_id); |
| match res { |
| Res::Def(DefKind::Ctor(CtorOf::Variant, ..), variant_ctor_did) => { |
| let variant_did = mc.tcx.parent(variant_ctor_did).unwrap(); |
| let downcast_cmt = mc.cat_downcast_if_needed(pat, cmt_pat, variant_did); |
| |
| debug!("variantctor downcast_cmt={:?} pat={:?}", downcast_cmt, pat); |
| delegate.matched_pat(pat, &downcast_cmt, match_mode); |
| } |
| Res::Def(DefKind::Variant, variant_did) => { |
| let downcast_cmt = mc.cat_downcast_if_needed(pat, cmt_pat, variant_did); |
| |
| debug!("variant downcast_cmt={:?} pat={:?}", downcast_cmt, pat); |
| delegate.matched_pat(pat, &downcast_cmt, match_mode); |
| } |
| Res::Def(DefKind::Struct, _) |
| | Res::Def(DefKind::Ctor(..), _) |
| | Res::Def(DefKind::Union, _) |
| | Res::Def(DefKind::TyAlias, _) |
| | Res::Def(DefKind::AssocTy, _) |
| | Res::SelfTy(..) => { |
| debug!("struct cmt_pat={:?} pat={:?}", cmt_pat, pat); |
| delegate.matched_pat(pat, &cmt_pat, match_mode); |
| } |
| _ => {} |
| } |
| })); |
| } |
| |
| fn walk_captures(&mut self, closure_expr: &hir::Expr, fn_decl_span: Span) { |
| debug!("walk_captures({:?})", closure_expr); |
| |
| let closure_def_id = self.tcx().hir().local_def_id(closure_expr.hir_id); |
| if let Some(upvars) = self.tcx().upvars(closure_def_id) { |
| for (&var_id, upvar) in upvars.iter() { |
| let upvar_id = ty::UpvarId { |
| var_path: ty::UpvarPath { hir_id: var_id }, |
| closure_expr_id: closure_def_id.to_local(), |
| }; |
| let upvar_capture = self.mc.tables.upvar_capture(upvar_id); |
| let cmt_var = return_if_err!(self.cat_captured_var(closure_expr.hir_id, |
| fn_decl_span, |
| var_id)); |
| match upvar_capture { |
| ty::UpvarCapture::ByValue => { |
| let mode = copy_or_move(&self.mc, |
| self.param_env, |
| &cmt_var, |
| CaptureMove); |
| self.delegate.consume(closure_expr.hir_id, upvar.span, &cmt_var, mode); |
| } |
| ty::UpvarCapture::ByRef(upvar_borrow) => { |
| self.delegate.borrow(closure_expr.hir_id, |
| fn_decl_span, |
| &cmt_var, |
| upvar_borrow.region, |
| upvar_borrow.kind, |
| ClosureCapture(upvar.span)); |
| } |
| } |
| } |
| } |
| } |
| |
| fn cat_captured_var(&mut self, |
| closure_hir_id: hir::HirId, |
| closure_span: Span, |
| var_id: hir::HirId) |
| -> mc::McResult<mc::cmt_<'tcx>> { |
| // Create the cmt for the variable being borrowed, from the |
| // perspective of the creator (parent) of the closure. |
| let var_ty = self.mc.node_ty(var_id)?; |
| self.mc.cat_res(closure_hir_id, closure_span, var_ty, Res::Local(var_id)) |
| } |
| } |
| |
| fn copy_or_move<'a, 'tcx>( |
| mc: &mc::MemCategorizationContext<'a, 'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| cmt: &mc::cmt_<'tcx>, |
| move_reason: MoveReason, |
| ) -> ConsumeMode { |
| if !mc.type_is_copy_modulo_regions(param_env, cmt.ty, cmt.span) { |
| Move(move_reason) |
| } else { |
| Copy |
| } |
| } |
