Rollup merge of rust-lang#69340 - Centril:self-ctor-normalize, r=niko…

…matsakis

instantiate_value_path: on `SelfCtor`, avoid unconstrained tyvars

Fixes rust-lang#69306.

On `Self(...)` (that is, a `Res::SelfCtor`), do not use `self.impl_self_ty(...)`. The problem with that method is that it creates unconstrained inference variables for type parameters in the `impl` (e.g. `impl<T> S0<T>`). These variables then eventually get substituted for something else when they come in contact with the expected type (e.g. `S0<u8>`) or merely the arguments passed to the tuple constructor (e.g. the `0` in `Self(0)`).

Instead of using `self.impl_self_ty(...)`, we instead merely use `let ty = self.normalize_ty(span, tcx.at(span).type_of(impl_def_id));` to get the rewritten `res`.

r? @eddyb

src/librustc_typeck/check/mod.rs

@@ -5447,9 +5447,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  .unwrap_or(false);
 
  let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
- let ty = self.impl_self_ty(span, impl_def_id).ty;
- let adt_def = ty.ty_adt_def();
-
+ let ty = self.normalize_ty(span, tcx.at(span).type_of(impl_def_id));
  match ty.kind {
  ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
  let variant = adt_def.non_enum_variant();
@@ -5464,7 +5462,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  span,
  "the `Self` constructor can only be used with tuple or unit structs",
  );
- if let Some(adt_def) = adt_def {
+ if let Some(adt_def) = ty.ty_adt_def() {
  match adt_def.adt_kind() {
  AdtKind::Enum => {
  err.help("did you mean to use one of the enum's variants?");

src/test/ui/issues/issue-69306.rs

@@ -0,0 +1,45 @@
+fn main() {}
+
+struct S0<T>(T);
+impl<T> S0<T> {
+ const C: S0<u8> = Self(0);
+ //~^ ERROR mismatched types
+ //~| ERROR mismatched types
+
+ fn foo() {
+ Self(0);
+ //~^ ERROR mismatched types
+ }
+}
+
+// Testing normalization.
+trait Fun {
+ type Out;
+}
+impl<T> Fun for S0<T> {
+ type Out = Self;
+}
+trait Foo<T> {
+ fn foo();
+}
+impl<T> Foo<T> for <S0<T> as Fun>::Out {
+ fn foo() {
+ Self(0); //~ ERROR mismatched types
+ }
+}
+
+struct S1<T, U>(T, U);
+impl<T> S1<T, u8> {
+ const C: S1<u8, u8> = Self(0, 1);
+ //~^ ERROR mismatched types
+ //~| ERROR mismatched types
+}
+
+struct S2<T>(T);
+impl<T> S2<T> {
+ fn map<U>(x: U) -> S2<U> {
+ Self(x)
+ //~^ ERROR mismatched types
+ //~| ERROR mismatched types
+ }
+}

src/test/ui/issues/issue-69306.stderr

@@ -0,0 +1,115 @@
+error[E0308]: mismatched types
+ --> $DIR/issue-69306.rs:5:28
+ |
+LL | impl<T> S0<T> {
+ | - this type parameter
+LL | const C: S0<u8> = Self(0);
+ | ^ expected type parameter `T`, found integer
+ |
+ = note: expected type parameter `T`
+ found type `{integer}`
+ = help: type parameters must be constrained to match other types
+ = note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
+
+error[E0308]: mismatched types
+ --> $DIR/issue-69306.rs:5:23
+ |
+LL | impl<T> S0<T> {
+ | - this type parameter
+LL | const C: S0<u8> = Self(0);
+ | ^^^^^^^ expected `u8`, found type parameter `T`
+ |
+ = note: expected struct `S0<u8>`
+ found struct `S0<T>`
+ = help: type parameters must be constrained to match other types
+ = note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
+
+error[E0308]: mismatched types
+ --> $DIR/issue-69306.rs:10:14
+ |
+LL | impl<T> S0<T> {
+ | - this type parameter
+...
+LL | Self(0);
+ | ^ expected type parameter `T`, found integer
+ |
+ = note: expected type parameter `T`
+ found type `{integer}`
+ = help: type parameters must be constrained to match other types
+ = note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
+
+error[E0308]: mismatched types
+ --> $DIR/issue-69306.rs:27:14
+ |
+LL | impl<T> Foo<T> for <S0<T> as Fun>::Out {
+ | - this type parameter
+LL | fn foo() {
+LL | Self(0);
+ | ^ expected type parameter `T`, found integer
+ |
+ = note: expected type parameter `T`
+ found type `{integer}`
+ = help: type parameters must be constrained to match other types
+ = note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
+
+error[E0308]: mismatched types
+ --> $DIR/issue-69306.rs:33:32
+ |
+LL | impl<T> S1<T, u8> {
+ | - this type parameter
+LL | const C: S1<u8, u8> = Self(0, 1);
+ | ^ expected type parameter `T`, found integer
+ |
+ = note: expected type parameter `T`
+ found type `{integer}`
+ = help: type parameters must be constrained to match other types
+ = note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
+
+error[E0308]: mismatched types
+ --> $DIR/issue-69306.rs:33:27
+ |
+LL | impl<T> S1<T, u8> {
+ | - this type parameter
+LL | const C: S1<u8, u8> = Self(0, 1);
+ | ^^^^^^^^^^ expected `u8`, found type parameter `T`
+ |
+ = note: expected struct `S1<u8, _>`
+ found struct `S1<T, _>`
+ = help: type parameters must be constrained to match other types
+ = note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
+
+error[E0308]: mismatched types
+ --> $DIR/issue-69306.rs:41:14
+ |
+LL | impl<T> S2<T> {
+ | - expected type parameter
+LL | fn map<U>(x: U) -> S2<U> {
+ | - found type parameter
+LL | Self(x)
+ | ^ expected type parameter `T`, found type parameter `U`
+ |
+ = note: expected type parameter `T`
+ found type parameter `U`
+ = note: a type parameter was expected, but a different one was found; you might be missing a type parameter or trait bound
+ = note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
+
+error[E0308]: mismatched types
+ --> $DIR/issue-69306.rs:41:9
+ |
+LL | impl<T> S2<T> {
+ | - found type parameter
+LL | fn map<U>(x: U) -> S2<U> {
+ | - ----- expected `S2<U>` because of return type
+ | |
+ | expected type parameter
+LL | Self(x)
+ | ^^^^^^^ expected type parameter `U`, found type parameter `T`
+ |
+ = note: expected struct `S2<U>`
+ found struct `S2<T>`
+ = note: a type parameter was expected, but a different one was found; you might be missing a type parameter or trait bound
+ = note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
+
+error: aborting due to 8 previous errors
+
+For more information about this error, try `rustc --explain E0308`.