Auto merge of #42807 - arielb1:consistent-coercion, r=eddyb

Coerce fields to the expected field type

Fully fixes #31260.

This needs a crater run. I was supposed to do this last month but it slipped. Let's get this done.

src/librustc_typeck/check/mod.rs

@@ -3125,11 +3125,13 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
  let adt_ty_hint =
  self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
- .get(0).cloned().unwrap_or(adt_ty);
+ .get(0).cloned().unwrap_or(adt_ty);
+ // re-link the regions that EIfEO can erase.
+ self.demand_eqtype(span, adt_ty_hint, adt_ty);
 
- let (substs, hint_substs, adt_kind, kind_name) = match (&adt_ty.sty, &adt_ty_hint.sty) {
- (&ty::TyAdt(adt, substs), &ty::TyAdt(_, hint_substs)) => {
- (substs, hint_substs, adt.adt_kind(), adt.variant_descr())
+ let (substs, adt_kind, kind_name) = match &adt_ty.sty{
+ &ty::TyAdt(adt, substs) => {
+ (substs, adt.adt_kind(), adt.variant_descr())
  }
  _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields")
  };
@@ -3145,14 +3147,8 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
  // Typecheck each field.
  for field in ast_fields {
- let final_field_type;
- let field_type_hint;
-
  let ident = tcx.adjust(field.name.node, variant.did, self.body_id).0;
- if let Some(v_field) = remaining_fields.remove(&ident) {
- final_field_type = self.field_ty(field.span, v_field, substs);
- field_type_hint = self.field_ty(field.span, v_field, hint_substs);
-
+ let field_type = if let Some(v_field) = remaining_fields.remove(&ident) {
  seen_fields.insert(field.name.node, field.span);
 
  // we don't look at stability attributes on
@@ -3161,10 +3157,10 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
  if adt_kind != ty::AdtKind::Enum {
  tcx.check_stability(v_field.did, expr_id, field.span);
  }
+
+ self.field_ty(field.span, v_field, substs)
  } else {
  error_happened = true;
- final_field_type = tcx.types.err;
- field_type_hint = tcx.types.err;
  if let Some(_) = variant.find_field_named(field.name.node) {
  let mut err = struct_span_err!(self.tcx.sess,
  field.name.span,
@@ -3182,12 +3178,13 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
  } else {
  self.report_unknown_field(adt_ty, variant, field, ast_fields, kind_name);
  }
- }
+
+ tcx.types.err
+ };
 
  // Make sure to give a type to the field even if there's
  // an error, so we can continue typechecking
- let ty = self.check_expr_with_hint(&field.expr, field_type_hint);
- self.demand_coerce(&field.expr, ty, final_field_type);
+ self.check_expr_coercable_to_type(&field.expr, field_type);
  }
 
  // Make sure the programmer specified correct number of fields.

src/test/run-pass/issue-31260.rs

@@ -12,9 +12,12 @@ pub struct Struct<K: 'static> {
  pub field: K,
 }
 
-// Partial fix for #31260, doesn't work without {...}.
 static STRUCT: Struct<&'static [u8]> = Struct {
  field: {&[1]}
 };
 
+static STRUCT2: Struct<&'static [u8]> = Struct {
+ field: &[1]
+};
+
 fn main() {}

src/test/ui/mismatched_types/abridged.rs

@@ -39,23 +39,25 @@ fn c() -> Result<Foo, Bar> {
 }
 
 fn d() -> X<X<String, String>, String> {
- X {
+ let x = X {
  x: X {
  x: "".to_string(),
  y: 2,
  },
  y: 3,
- }
+ };
+ x
 }
 
 fn e() -> X<X<String, String>, String> {
- X {
+ let x = X {
  x: X {
  x: "".to_string(),
  y: 2,
  },
  y: "".to_string(),
- }
+ };
+ x
 }
 
 fn main() {}

src/test/ui/mismatched_types/abridged.stderr

@@ -35,31 +35,19 @@ error[E0308]: mismatched types
  found type `Foo`
 
 error[E0308]: mismatched types
- --> $DIR/abridged.rs:42:5
+ --> $DIR/abridged.rs:49:5
  |
-42 | / X {
-43 | | x: X {
-44 | | x: "".to_string(),
-45 | | y: 2,
-46 | | },
-47 | | y: 3,
-48 | | }
- | |_____^ expected struct `std::string::String`, found integral variable
+49 | x
+ | ^ expected struct `std::string::String`, found integral variable
  |
  = note: expected type `X<X<_, std::string::String>, std::string::String>`
  found type `X<X<_, {integer}>, {integer}>`
 
 error[E0308]: mismatched types
- --> $DIR/abridged.rs:52:5
+ --> $DIR/abridged.rs:60:5
  |
-52 | / X {
-53 | | x: X {
-54 | | x: "".to_string(),
-55 | | y: 2,
-56 | | },
-57 | | y: "".to_string(),
-58 | | }
- | |_____^ expected struct `std::string::String`, found integral variable
+60 | x
+ | ^ expected struct `std::string::String`, found integral variable
  |
  = note: expected type `X<X<_, std::string::String>, _>`
  found type `X<X<_, {integer}>, _>`