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Rollup merge of #87557 - rylev:fix-invalid-prelude-collision-error, r=nikomatsakis

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Fix issue with autofix for ambiguous associated function from Rust 2021 prelude when struct is generic

Fixes #86940

The test cases and associated issue should make it clear what specifically this is meant to fix. The fix is slightly hacky in that we check against the literal source code of the call site for the presence of `<` in order to determine if the user has included the generics for the struct (meaning we don't need to include them for them).

r? ``@nikomatsakis``
This commit is contained in:
Yuki Okushi 2021-07-31 04:09:29 +09:00 • committed by GitHub
commit fb27c4cc70
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5 changed files with 126 additions and 3 deletions
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21
compiler/rustc_typeck/src/check/method/prelude2021.rs
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@ -5,7 +5,7 @@ use rustc_ast::Mutability;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_middle::ty::subst::InternalSubsts;
use rustc_middle::ty::{Ref, Ty};
use rustc_middle::ty::{Adt, Ref, Ty};
use rustc_session::lint::builtin::RUST_2021_PRELUDE_COLLISIONS;
use rustc_span::symbol::kw::Underscore;
use rustc_span::symbol::{sym, Ident};
@ -255,16 +255,31 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
method_name.name
));
let self_ty = self
let self_ty_name = self
.sess()
.source_map()
.span_to_snippet(self_ty_span)
.unwrap_or_else(|_| self_ty.to_string());
let self_ty_generics_count = match self_ty.kind() {
// Get the number of generics the self type has (if an Adt) unless we can determine that
// the user has written the self type with generics already which we (naively) do by looking
// for a "<" in `self_ty_name`.
Adt(def, _) if !self_ty_name.contains("<") => self.tcx.generics_of(def.did).count(),
_ => 0,
};
let self_ty_generics = if self_ty_generics_count > 0 {
format!("<{}>", vec!["_"; self_ty_generics_count].join(", "))
} else {
String::new()
};
lint.span_suggestion(
span,
"disambiguate the associated function",
format!("<{} as {}>::{}", self_ty, trait_name, method_name.name,),
format!(
"<{}{} as {}>::{}",
self_ty_name, self_ty_generics, trait_name, method_name.name,
),
Applicability::MachineApplicable,
);