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Instability warning for let bindings in const fn doesn't list requisite feature flag #57544

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varkor opened this issue Jan 12, 2019 · 1 comment
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Instability warning for let bindings in const fn doesn't list requisite feature flag #57544

varkor opened this issue Jan 12, 2019 · 1 comment
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A-const-fn Area: const fn foo(..) {..}. Pure functions which can be applied at compile time. A-diagnostics Area: Messages for errors, warnings, and lints

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@varkor
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varkor commented Jan 12, 2019 

const fn foo() {
    let _x = 5;
}

reports:

error: local variables in const fn are unstable
 --> src/lib.rs:2:9
  |
2 |     let _x = 5;
  |         ^^

error: aborting due to previous error

This should report to the user which feature flag should be added to use this feature.
@varkor varkor added A-diagnostics Area: Messages for errors, warnings, and lints A-const-fn Area: const fn foo(..) {..}. Pure functions which can be applied at compile time. labels Jan 12, 2019
@Centril
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Centril commented Jan 13, 2019

They are stable on nightly anyways so there might not be anything to fix here?

@varkor varkor mentioned this issue Feb 6, 2019
Merged
Centril added a commit to Centril/rust that referenced this issue Feb 13, 2019
@Centril
Rollup merge of rust-lang#58196 - varkor:const-fn-feature-gate-error,…
a92a40d 
… r=oli-obk

Add specific feature gate error for const-unstable features

Before:
```
error: `impl Trait` in const fn is unstable
 --> src/lib.rs:7:19
  |
7 | const fn foo() -> impl T {
  |                   ^^^^^^

error: aborting due to previous error
```

After:
```
error[E0723]: `impl Trait` in const fn is unstable (see issue rust-lang#57563)
 --> src/lib.rs:7:19
  |
7 | const fn foo() -> impl T {
  |                   ^^^^^^
  = help: add #![feature(const_fn)] to the crate attributes to enable

error: aborting due to previous error
```

This improves the situation with rust-lang#57563. Fixes rust-lang#57544. Fixes rust-lang#54469.

r? @oli-obk
Centril added a commit to Centril/rust that referenced this issue Feb 13, 2019
@Centril
Rollup merge of rust-lang#58196 - varkor:const-fn-feature-gate-error,…
937838f 
… r=oli-obk

Add specific feature gate error for const-unstable features

Before:
```
error: `impl Trait` in const fn is unstable
 --> src/lib.rs:7:19
  |
7 | const fn foo() -> impl T {
  |                   ^^^^^^

error: aborting due to previous error
```

After:
```
error[E0723]: `impl Trait` in const fn is unstable (see issue rust-lang#57563)
 --> src/lib.rs:7:19
  |
7 | const fn foo() -> impl T {
  |                   ^^^^^^
  = help: add #![feature(const_fn)] to the crate attributes to enable

error: aborting due to previous error
```

This improves the situation with rust-lang#57563. Fixes rust-lang#57544. Fixes rust-lang#54469.

r? @oli-obk
Centril added a commit to Centril/rust that referenced this issue Feb 14, 2019
@Centril
Rollup merge of rust-lang#58196 - varkor:const-fn-feature-gate-error,…
634022c 
… r=oli-obk

Add specific feature gate error for const-unstable features

Before:
```
error: `impl Trait` in const fn is unstable
 --> src/lib.rs:7:19
  |
7 | const fn foo() -> impl T {
  |                   ^^^^^^

error: aborting due to previous error
```

After:
```
error[E0723]: `impl Trait` in const fn is unstable (see issue rust-lang#57563)
 --> src/lib.rs:7:19
  |
7 | const fn foo() -> impl T {
  |                   ^^^^^^
  = help: add #![feature(const_fn)] to the crate attributes to enable

error: aborting due to previous error
```

This improves the situation with rust-lang#57563. Fixes rust-lang#57544. Fixes rust-lang#54469.

r? @oli-obk
kennytm added a commit to kennytm/rust that referenced this issue Feb 16, 2019
@kennytm
Rollup merge of rust-lang#58196 - varkor:const-fn-feature-gate-error,…
49107c3 
… r=oli-obk

Add specific feature gate error for const-unstable features

Before:
```
error: `impl Trait` in const fn is unstable
 --> src/lib.rs:7:19
  |
7 | const fn foo() -> impl T {
  |                   ^^^^^^

error: aborting due to previous error
```

After:
```
error[E0723]: `impl Trait` in const fn is unstable (see issue rust-lang#57563)
 --> src/lib.rs:7:19
  |
7 | const fn foo() -> impl T {
  |                   ^^^^^^
  = help: add #![feature(const_fn)] to the crate attributes to enable

error: aborting due to previous error
```

This improves the situation with rust-lang#57563. Fixes rust-lang#57544. Fixes rust-lang#54469.

r? @oli-obk
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