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Better handle type errors involving Self literals #117959

Merged
merged 3 commits into from
Nov 17, 2023
Merged

Better handle type errors involving Self literals #117959

merged 3 commits into from
Nov 17, 2023

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estebank
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When encountering a type error involving a Self literal, point at the self type of the enclosing impl and suggest using the actual type name instead.

error[E0308]: mismatched types
  --> $DIR/struct-path-self-type-mismatch.rs:13:9
   |
LL |   impl<T> Foo<T> {
   |        -  ------ this is the type of the `Self` literal
   |        |
   |        found type parameter
LL |       fn new<U>(u: U) -> Foo<U> {
   |              -           ------ expected `Foo<U>` because of return type
   |              |
   |              expected type parameter
LL | /         Self {
LL | |
LL | |             inner: u
LL | |
LL | |         }
   | |_________^ expected `Foo<U>`, found `Foo<T>`
   |
   = note: expected struct `Foo<U>`
              found struct `Foo<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
help: use the type name directly
   |
LL |         Foo::<U> {
   |         ~~~~~~~~

Fix #76086.

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rustbot commented Nov 16, 2023

r? @TaKO8Ki

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@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Nov 16, 2023
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@estebank
Point at impl self ty on type error involving Self
a7e035a 
When encountering a type error involving a `Self` literal, point at the
self type of the enclosing `impl`.

CC rust-lang#76086.
@estebank
Suggest replacing Self with the right type on type error
d845685 
When encountering a type error caused by the use of `Self`, suggest
using the actual type name instead.

```
error[E0308]: mismatched types
  --> $DIR/struct-path-self-type-mismatch.rs:13:9
   |
LL |   impl<T> Foo<T> {
   |        -  ------ this is the type of the `Self` literal
   |        |
   |        found type parameter
LL |       fn new<U>(u: U) -> Foo<U> {
   |              -           ------ expected `Foo<U>` because of return type
   |              |
   |              expected type parameter
LL | /         Self {
LL | |
LL | |             inner: u
LL | |
LL | |         }
   | |_________^ expected `Foo<U>`, found `Foo<T>`
   |
   = note: expected struct `Foo<U>`
              found struct `Foo<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
help: use the type name directly
   |
LL |         Foo::<U> {
   |         ~~~~~~~~
```

Fix rust-lang#76086.
compiler-errors
compiler-errors requested changes Nov 16, 2023
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r=me after moving the call

compiler/rustc_hir_typeck/src/coercion.rs Outdated
@@ -1738,6 +1740,7 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
// label pointing out the cause for the type coercion will be wrong
// as prior return coercions would not be relevant (#57664).
let fn_decl = if let (Some(expr), Some(blk_id)) = (expression, blk_id) {
self.explain_self_literal(fcx, &mut err, expr, expected, found);
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I feel like a better location for this is with the rest of the mismatch suggestions in emit_type_mismatch_suggestions.

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@bors r=compiler-errors

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bors commented Nov 16, 2023

📌 Commit 1e8c095 has been approved by compiler-errors

It is now in the queue for this repository.

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 16, 2023
@matthiaskrgr matthiaskrgr mentioned this pull request Nov 16, 2023
Merged
bors added a commit to rust-lang-ci/rust that referenced this pull request Nov 17, 2023
@bors
Auto merge of rust-lang#117996 - matthiaskrgr:rollup-sp48bl4, r=matth…
f2f526c 
…iaskrgr

Rollup of 5 pull requests

Successful merges:

 - rust-lang#117892 (Detect more `=>` typos)
 - rust-lang#117959 (Better handle type errors involving `Self` literals)
 - rust-lang#117980 (fix: Update CONTRIBUTING.md recommend -> recommended)
 - rust-lang#117982 (bootstrap: only show PGO warnings when verbose)
 - rust-lang#117990 (Tweak error and move tests)

Failed merges:

 - rust-lang#117944 (some additional region refactorings)

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit dd49c39 into rust-lang:master Nov 17, 2023
11 checks passed
@rustbot rustbot added this to the 1.76.0 milestone Nov 17, 2023
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Nov 17, 2023
@rust-timer
Unrolled build for rust-lang#117959
5c91d0d 
Rollup merge of rust-lang#117959 - estebank:issue-76086, r=compiler-errors

Better handle type errors involving `Self` literals

When encountering a type error involving a `Self` literal, point at the self type of the enclosing `impl` and suggest using the actual type name instead.

```
error[E0308]: mismatched types
  --> $DIR/struct-path-self-type-mismatch.rs:13:9
   |
LL |   impl<T> Foo<T> {
   |        -  ------ this is the type of the `Self` literal
   |        |
   |        found type parameter
LL |       fn new<U>(u: U) -> Foo<U> {
   |              -           ------ expected `Foo<U>` because of return type
   |              |
   |              expected type parameter
LL | /         Self {
LL | |
LL | |             inner: u
LL | |
LL | |         }
   | |_________^ expected `Foo<U>`, found `Foo<T>`
   |
   = note: expected struct `Foo<U>`
              found struct `Foo<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
help: use the type name directly
   |
LL |         Foo::<U> {
   |         ~~~~~~~~
```
Fix rust-lang#76086.
@lqd lqd mentioned this pull request Mar 14, 2024
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Misleading type error when generic parameter is sole mismatch.
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