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Tweak suggest_constraining_type_param#70009

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estebank:sugg-bound
Mar 30, 2020
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Tweak suggest_constraining_type_param#70009
bors merged 1 commit intorust-lang:masterfrom
estebank:sugg-bound

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@estebank estebank commented Mar 14, 2020

Some of the bound restriction structured suggestions were incorrect while others had subpar output.

The only issue left is a suggestion for an already present bound when dealing with consts that should be handled independently.

Fix #69983.

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@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Mar 14, 2020
@Centril Centril self-assigned this Mar 18, 2020
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Centril reviewed Mar 24, 2020
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@Centril Centril added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Mar 24, 2020
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src/librustc_trait_selection/traits/error_reporting/suggestions.rs
Comment on lines +219 to +229
hir::Item { kind: hir::ItemKind::Struct(_, generics), .. }
| hir::Item { kind: hir::ItemKind::Enum(_, generics), .. }
| hir::Item { kind: hir::ItemKind::Union(_, generics), .. }
| hir::Item { kind: hir::ItemKind::Trait(_, _, generics, ..), .. }
| hir::Item { kind: hir::ItemKind::Impl { generics, .. }, .. }
| hir::Item { kind: hir::ItemKind::Fn(_, generics, _), .. }
| hir::Item { kind: hir::ItemKind::TyAlias(_, generics), .. }
| hir::Item { kind: hir::ItemKind::TraitAlias(generics, _), .. }
| hir::Item {
kind: hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. }), ..
},
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nit: you can further simplify this by moving the or-pattern all the way into the kind: field-pattern (same above).

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I tried that first but I got a syntax error so I assumed it wasn't possible.

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Huh, that shouldn't happen... Let's merge this without and I'll see what's up with this myself.

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Centril commented Mar 26, 2020

r=me with final nit addressed. :)

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estebank commented Mar 26, 2020

@bors r=Centril

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bors commented Mar 26, 2020

📌 Commit 293cf51 has been approved by Centril

@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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Mar 26, 2020
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bors commented Mar 27, 2020

⌛ Testing commit 293cf51 with merge 1a69ea894186a265cbff1be75029e1e889a0bf5b...

Centril added a commit to Centril/rust that referenced this pull request Mar 27, 2020
@Centril
Rollup merge of rust-lang#70009 - estebank:sugg-bound, r=Centril
b366675 
Tweak `suggest_constraining_type_param`

Some of the bound restriction structured suggestions were incorrect while others had subpar output.

The only issue left is a suggestion for an already present bound when dealing with `const`s that should be handled independently.

Fix rust-lang#69983.
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Centril commented Mar 27, 2020

@bors retry

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Centril commented Mar 27, 2020

Failed in #70481 (comment), @bors r-

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estebank commented Mar 29, 2020

It seems like --compare-mode=nll discrepancy. Rebasing and fixing.

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Tweak suggest_constraining_type_param
2c71894 
Some of the bound restriction structured suggestions were incorrect
while others had subpar output.
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estebank commented Mar 29, 2020

@bors r=Centril

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bors commented Mar 29, 2020

📌 Commit 2c71894 has been approved by Centril

@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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Mar 29, 2020
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bors commented Mar 29, 2020

⌛ Testing commit 2c71894 with merge 4911572...

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bors commented Mar 30, 2020

☀️ Test successful - checks-azure
Approved by: Centril
Pushing 4911572 to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label Mar 30, 2020
@bors bors merged commit 4911572 into rust-lang:master Mar 30, 2020
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@iximeow iximeow mentioned this pull request Sep 14, 2020
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Dylan-DPC-zz pushed a commit to Dylan-DPC-zz/rust that referenced this pull request Sep 16, 2020
@Dylan-DPC
Rollup merge of rust-lang#76695 - iximeow:trait-generic-bound-suggest…
f4be98a 
…ion, r=estebank

fix syntax error in suggesting generic constraint in trait parameter

suggest `where T: Foo` for the first bound on a trait, then suggest
`, T: Foo` when the suggested bound would add to an existing set of
`where` clauses. `where T: Foo` may be the first bound if `T` has a
default, because we'd rather suggest
```
trait A<T=()> where T: Copy
```
than
```
trait A<T: Copy=()>
```
for legibility reasons.

the test case i added here is derived from [this reproduction](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=0bf3ace9f2a183d0bdbd748c6b8e3971):
```
struct B<T: Copy> {
    t: T
}

trait A<T = ()> {
    fn returns_constrained_type(&self, t: T) -> B<T> {
        B { t }
    }
}
```
where the suggested fix,
```
trait A<T = ()>, T: Copy { ... }
```
is in fact invalid syntax!

i also found an error in the existing suggestion for `trait Base<T = String>: Super<T>` where rustc would suggest `trait Base<T = String>: Super<T>, T: Copy`, but `T: Copy` is the first of the trait's `where` clauses and should be `where T: Copy` as well. the test for that suggestion expects invalid syntax, and has been revised to a compiler-pleasing `trait Base<T = String>: Super<T> where T: Copy`.

judging by rust-lang#70009 i'll.. cc @estebank ?
Dylan-DPC-zz pushed a commit to Dylan-DPC-zz/rust that referenced this pull request Sep 16, 2020
@Dylan-DPC
Rollup merge of rust-lang#76695 - iximeow:trait-generic-bound-suggest…
54d7728 
…ion, r=estebank

fix syntax error in suggesting generic constraint in trait parameter

suggest `where T: Foo` for the first bound on a trait, then suggest
`, T: Foo` when the suggested bound would add to an existing set of
`where` clauses. `where T: Foo` may be the first bound if `T` has a
default, because we'd rather suggest
```
trait A<T=()> where T: Copy
```
than
```
trait A<T: Copy=()>
```
for legibility reasons.

the test case i added here is derived from [this reproduction](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=0bf3ace9f2a183d0bdbd748c6b8e3971):
```
struct B<T: Copy> {
    t: T
}

trait A<T = ()> {
    fn returns_constrained_type(&self, t: T) -> B<T> {
        B { t }
    }
}
```
where the suggested fix,
```
trait A<T = ()>, T: Copy { ... }
```
is in fact invalid syntax!

i also found an error in the existing suggestion for `trait Base<T = String>: Super<T>` where rustc would suggest `trait Base<T = String>: Super<T>, T: Copy`, but `T: Copy` is the first of the trait's `where` clauses and should be `where T: Copy` as well. the test for that suggestion expects invalid syntax, and has been revised to a compiler-pleasing `trait Base<T = String>: Super<T> where T: Copy`.

judging by rust-lang#70009 i'll.. cc @estebank ?
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help text for Send trait bound mismatch is misleading

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