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Rollup merge of #126054 - veera-sivarajan:bugfix-113073-bound-on-generics-2, r=fee1-dead

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`E0229`: Suggest Moving Type Constraints to Type Parameter Declaration

Fixes #113073

This PR suggests  `impl<T: Bound> Trait<T> for Foo` when finding `impl Trait<T: Bound> for Foo`. Tangentially, it also improves a handful of other error messages.

It accomplishes this in two steps:
1. Check if constrained arguments and parameter names appear in the same order and delay emitting "incorrect number of generic arguments" error because it can be confusing for the programmer to see `0 generic arguments provided` when there are `n` constrained generic arguments.

2. Inside `E0229`, suggest declaring the type parameter right after the `impl` keyword by finding the relevant impl block's span for type parameter declaration. This also handles lifetime declarations correctly.

Also, the multi part suggestion doesn't use the fluent error mechanism because translating all the errors to fluent style feels outside the scope of this PR. I will handle it in a separate PR if this gets approved.
This commit is contained in:
Matthias Krüger 2024-06-14 12:23:36 +02:00 • committed by GitHub
commit bfe032334f
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14 changed files with 263 additions and 101 deletions
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24
compiler/rustc_hir/src/hir.rs
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@ -2471,6 +2471,15 @@ pub enum AssocItemConstraintKind<'hir> {
Bound { bounds: &'hir [GenericBound<'hir>] },
}
impl<'hir> AssocItemConstraintKind<'hir> {
pub fn descr(&self) -> &'static str {
match self {
AssocItemConstraintKind::Equality { .. } => "binding",
AssocItemConstraintKind::Bound { .. } => "constraint",
}
}
}
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Ty<'hir> {
pub hir_id: HirId,
@ -3763,6 +3772,21 @@ impl<'hir> Node<'hir> {
}
}
/// Get a `hir::Impl` if the node is an impl block for the given `trait_def_id`.
pub fn impl_block_of_trait(self, trait_def_id: DefId) -> Option<&'hir Impl<'hir>> {
match self {
Node::Item(Item { kind: ItemKind::Impl(impl_block), .. })
if impl_block
.of_trait
.and_then(|trait_ref| trait_ref.trait_def_id())
.is_some_and(|trait_id| trait_id == trait_def_id) =>
{
Some(impl_block)
}
_ => None,
}
}
pub fn fn_sig(self) -> Option<&'hir FnSig<'hir>> {
match self {
Node::TraitItem(TraitItem { kind: TraitItemKind::Fn(fn_sig, _), .. })