Further dedup unsized locals errors involving method calls

Author: estebank

compiler/rustc_hir_typeck/src/gather_locals.rs

@@ -142,22 +142,32 @@ impl<'a, 'tcx> GatherLocalsVisitor<'a, 'tcx> {
  self.fcx.ty_to_string(*self.fcx.locals.borrow().get(&decl.hir_id).unwrap())
  );
  }
+
+ fn span_for_init_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Span {
+ // In other parts of the compiler, when emitting a bound error on a method call we point at
+ // the method call path. We mimic that here so that error deduplication will work as
+ // expected.
+ match expr.kind {
+ hir::ExprKind::MethodCall(path, ..) => path.ident.span,
+ _ => expr.span,
+ }
+ }
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
  // Add explicitly-declared locals.
  fn visit_local(&mut self, local: &'tcx hir::Local<'tcx>) {
  self.declare(local.into());
  let sp = self.let_binding_init.take();
- self.let_binding_init = local.init.map(|e| e.span);
+ self.let_binding_init = local.init.map(|e| self.span_for_init_expr(e));
  intravisit::walk_local(self, local);
  self.let_binding_init = sp;
  }
 
  fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
  let sp = self.let_binding_init.take();
  if let hir::ExprKind::Let(let_expr) = expr.kind {
- self.let_binding_init = Some(let_expr.init.span);
+ self.let_binding_init = Some(self.span_for_init_expr(&let_expr.init));
  self.declare((let_expr, expr.hir_id).into());
  }
  intravisit::walk_expr(self, expr);

compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs

@@ -138,6 +138,12 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
  span = local.pat.span;
  }
  }
+ ObligationCauseCode::ExprBindingObligation(_, _, hir_id, _) => {
+ // For method calls like `let x = y.foo();` that are `?Sized`, we also dedup
+ if let hir::Node::Local(local) = self.tcx.parent_hir_node(*hir_id) {
+ span = local.pat.span;
+ }
+ }
  _ => {}
  }
  }

tests/ui/associated-types/associated-types-unsized.stderr

@@ -1,8 +1,8 @@
 error[E0277]: the size for values of type `<T as Get>::Value` cannot be known at compilation time
- --> $DIR/associated-types-unsized.rs:10:13
+ --> $DIR/associated-types-unsized.rs:10:15
  |
 LL | let x = t.get();
- | ^^^^^^^ doesn't have a size known at compile-time
+ |  ^^^ doesn't have a size known at compile-time
  |
  = help: the trait `Sized` is not implemented for `<T as Get>::Value`
  = note: all local variables must have a statically known size

tests/ui/error-codes/E0038.stderr

@@ -29,10 +29,10 @@ LL | fn foo(&self) -> Self;
  = help: consider moving `foo` to another trait
 
 error[E0277]: the size for values of type `dyn Trait` cannot be known at compilation time
- --> $DIR/E0038.rs:7:13
+ --> $DIR/E0038.rs:7:15
  |
 LL | let y = x.foo();
- | ^^^^^^^ doesn't have a size known at compile-time
+ |  ^^^ doesn't have a size known at compile-time
  |
  = help: the trait `Sized` is not implemented for `dyn Trait`
  = note: all local variables must have a statically known size

tests/ui/iterators/collect-into-slice.rs

@@ -5,14 +5,11 @@ fn process_slice(data: &[i32]) {
 fn main() {
  let some_generated_vec = (0..10).collect();
  //~^ ERROR the size for values of type `[i32]` cannot be known at compilation time
- //~| ERROR the size for values of type `[i32]` cannot be known at compilation time
  //~| ERROR a slice of type `[i32]` cannot be built since `[i32]` has no definite size
  //~| NOTE try explicitly collecting into a `Vec<{integer}>`
- //~| NOTE required by an implicit `Sized` bound in `collect`
  //~| NOTE required by a bound in `collect`
  //~| NOTE all local variables must have a statically known size
  //~| NOTE doesn't have a size known at compile-time
- //~| NOTE doesn't have a size known at compile-time
  process_slice(&some_generated_vec);
 
  let some_generated_vec = (0..10).collect();

tests/ui/iterators/collect-into-slice.stderr

@@ -8,28 +8,18 @@ LL | let some_generated_vec = (0..10).collect();
 note: required by a bound in `collect`
  --> $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
 
-error[E0277]: the size for values of type `[i32]` cannot be known at compilation time
- --> $DIR/collect-into-slice.rs:6:30
- |
-LL | let some_generated_vec = (0..10).collect();
- | ^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
- |
- = help: the trait `Sized` is not implemented for `[i32]`
- = note: all local variables must have a statically known size
- = help: unsized locals are gated as an unstable feature
-
 error[E0277]: the size for values of type `[i32]` cannot be known at compilation time
  --> $DIR/collect-into-slice.rs:6:38
  |
 LL | let some_generated_vec = (0..10).collect();
  | ^^^^^^^ doesn't have a size known at compile-time
  |
  = help: the trait `Sized` is not implemented for `[i32]`
-note: required by an implicit `Sized` bound in `collect`
- --> $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
+ = note: all local variables must have a statically known size
+  = help: unsized locals are gated as an unstable feature
 
 error[E0277]: a slice of type `&[i32]` cannot be built since we need to store the elements somewhere
- --> $DIR/collect-into-slice.rs:18:38
+ --> $DIR/collect-into-slice.rs:15:38
  |
 LL | let some_generated_vec = (0..10).collect();
  | ^^^^^^^ try explicitly collecting into a `Vec<{integer}>`
@@ -38,6 +28,6 @@ LL | let some_generated_vec = (0..10).collect();
 note: required by a bound in `collect`
  --> $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
 
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0277`.