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Fix some non-determinism in help messages for E0277 errors.

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The diagnostic for this error prints `the following implementations
were found` followed by the first N relevant impls, sorted.

This commit makes the sort happen before slicing,
so that the set of impls being printed is deterministic
when the input is not.
This commit is contained in:
Simon Sapin 2019-01-21 16:55:32 +01:00
parent 9be4c76910
commit e195ce654a
4 changed files with 11 additions and 7 deletions
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10
src/librustc/traits/error_reporting.rs
View file

@ -471,7 +471,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
}
fn report_similar_impl_candidates(&self,
mut impl_candidates: Vec<ty::TraitRef<'tcx>>,
impl_candidates: Vec<ty::TraitRef<'tcx>>,
err: &mut DiagnosticBuilder<'_>)
{
if impl_candidates.is_empty() {
@ -497,14 +497,18 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
});
// Sort impl candidates so that ordering is consistent for UI tests.
let normalized_impl_candidates = &mut impl_candidates[0..end]
let mut normalized_impl_candidates = impl_candidates
.iter()
.map(normalize)
.collect::<Vec<String>>();
// Sort before taking the `..end` range,
// because the ordering of `impl_candidates` may not be deterministic:
// https://github.com/rust-lang/rust/pull/57475#issuecomment-455519507
normalized_impl_candidates.sort();
err.help(&format!("the following implementations were found:{}{}",
normalized_impl_candidates.join(""),
normalized_impl_candidates[..end].join(""),
if len > 5 {
format!("\nand {} others", len - 4)
} else {

2
src/test/ui/did_you_mean/issue-21659-show-relevant-trait-impls-2.stderr
View file

@ -8,7 +8,7 @@ LL | f1.foo(1usize);
<Bar as Foo<i16>>
<Bar as Foo<i32>>
<Bar as Foo<i8>>
<Bar as Foo<u8>>
<Bar as Foo<u16>>
and 2 others
error: aborting due to previous error

4
src/test/ui/did_you_mean/issue-39802-show-5-trait-impls.stderr
View file

@ -40,10 +40,10 @@ LL | Foo::<i32>::bar(&true); //~ ERROR is not satisfied
| ^^^^^^^^^^^^^^^ the trait `Foo<i32>` is not implemented for `bool`
|
= help: the following implementations were found:
<bool as Foo<bool>>
<bool as Foo<i8>>
<bool as Foo<u16>>
<bool as Foo<u32>>
<bool as Foo<u64>>
<bool as Foo<u8>>
and 2 others
note: required by `Foo::bar`
--> $DIR/issue-39802-show-5-trait-impls.rs:2:5

2
src/test/ui/try-block/try-block-bad-type.stderr
View file

@ -5,10 +5,10 @@ LL | Err("")?; //~ ERROR the trait bound `i32: std::convert::From<&str>`
| ^^^^^^^^ the trait `std::convert::From<&str>` is not implemented for `i32`
|
= help: the following implementations were found:
<i32 as std::convert::From<bool>>
<i32 as std::convert::From<core::num::NonZeroI32>>
<i32 as std::convert::From<i16>>
<i32 as std::convert::From<i8>>
<i32 as std::convert::From<u8>>
and 2 others
= note: required by `std::convert::From::from`