From ee7e717322f83d4b055e15b9948c07dd59118a5c Mon Sep 17 00:00:00 2001
From: Lukas Markeffsky <@>
Date: Wed, 14 Jun 2023 08:03:35 +0000
Subject: [PATCH] tweak suggestion for argument-position `impl ?Sized`
---
compiler/rustc_middle/src/ty/diagnostics.rs | 41 +++++++++++++++------
tests/ui/trait-bounds/apit-unsized.rs | 4 ++
tests/ui/trait-bounds/apit-unsized.stderr | 41 +++++++++++++++++++++
3 files changed, 74 insertions(+), 12 deletions(-)
create mode 100644 tests/ui/trait-bounds/apit-unsized.rs
create mode 100644 tests/ui/trait-bounds/apit-unsized.stderr
diff --git a/compiler/rustc_middle/src/ty/diagnostics.rs b/compiler/rustc_middle/src/ty/diagnostics.rs
index 9c948dba1e4..1c80692c306 100644
--- a/compiler/rustc_middle/src/ty/diagnostics.rs
+++ b/compiler/rustc_middle/src/ty/diagnostics.rs
@@ -14,8 +14,8 @@ use rustc_errors::{Applicability, Diagnostic, DiagnosticArgValue, IntoDiagnostic
use rustc_hir as hir;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::DefId;
-use rustc_hir::WherePredicate;
-use rustc_span::Span;
+use rustc_hir::{PredicateOrigin, WherePredicate};
+use rustc_span::{BytePos, Span};
use rustc_type_ir::sty::TyKind::*;
impl<'tcx> IntoDiagnosticArg for Ty<'tcx> {
@@ -156,10 +156,11 @@ enum SuggestChangingConstraintsMessage<'a> {
RestrictBoundFurther,
RestrictType { ty: &'a str },
RestrictTypeFurther { ty: &'a str },
- RemovingQSized,
+ RemoveMaybeUnsized,
+ ReplaceMaybeUnsizedWithSized,
}
-fn suggest_removing_unsized_bound(
+fn suggest_changing_unsized_bound(
generics: &hir::Generics<'_>,
suggestions: &mut Vec<(Span, String, SuggestChangingConstraintsMessage<'_>)>,
param: &hir::GenericParam<'_>,
@@ -183,12 +184,25 @@ fn suggest_removing_unsized_bound(
if poly.trait_ref.trait_def_id() != def_id {
continue;
}
- let sp = generics.span_for_bound_removal(where_pos, pos);
- suggestions.push((
- sp,
- String::new(),
- SuggestChangingConstraintsMessage::RemovingQSized,
- ));
+ if predicate.origin == PredicateOrigin::ImplTrait && predicate.bounds.len() == 1 {
+ // For `impl ?Sized` with no other bounds, suggest `impl Sized` instead.
+ let bound_span = bound.span();
+ if bound_span.can_be_used_for_suggestions() {
+ let question_span = bound_span.with_hi(bound_span.lo() + BytePos(1));
+ suggestions.push((
+ question_span,
+ String::new(),
+ SuggestChangingConstraintsMessage::ReplaceMaybeUnsizedWithSized,
+ ));
+ }
+ } else {
+ let sp = generics.span_for_bound_removal(where_pos, pos);
+ suggestions.push((
+ sp,
+ String::new(),
+ SuggestChangingConstraintsMessage::RemoveMaybeUnsized,
+ ));
+ }
}
}
}
@@ -245,7 +259,7 @@ pub fn suggest_constraining_type_params<'a>(
param.span,
format!("this type parameter needs to be `{}`", constraint),
);
- suggest_removing_unsized_bound(generics, &mut suggestions, param, def_id);
+ suggest_changing_unsized_bound(generics, &mut suggestions, param, def_id);
}
}
@@ -395,9 +409,12 @@ pub fn suggest_constraining_type_params<'a>(
SuggestChangingConstraintsMessage::RestrictTypeFurther { ty } => {
Cow::from(format!("consider further restricting type parameter `{}`", ty))
}
- SuggestChangingConstraintsMessage::RemovingQSized => {
+ SuggestChangingConstraintsMessage::RemoveMaybeUnsized => {
Cow::from("consider removing the `?Sized` bound to make the type parameter `Sized`")
}
+ SuggestChangingConstraintsMessage::ReplaceMaybeUnsizedWithSized => {
+ Cow::from("consider replacing `?Sized` with `Sized`")
+ }
};
err.span_suggestion_verbose(span, msg, suggestion, applicability);
diff --git a/tests/ui/trait-bounds/apit-unsized.rs b/tests/ui/trait-bounds/apit-unsized.rs
new file mode 100644
index 00000000000..469d6a6345e
--- /dev/null
+++ b/tests/ui/trait-bounds/apit-unsized.rs
@@ -0,0 +1,4 @@
+fn foo(_: impl Iterator<Item = i32> + ?Sized) {} //~ ERROR [E0277]
+fn bar(_: impl ?Sized) {} //~ ERROR [E0277]
+
+fn main() {}
diff --git a/tests/ui/trait-bounds/apit-unsized.stderr b/tests/ui/trait-bounds/apit-unsized.stderr
new file mode 100644
index 00000000000..7a4a2274d44
--- /dev/null
+++ b/tests/ui/trait-bounds/apit-unsized.stderr
@@ -0,0 +1,41 @@
+error[E0277]: the size for values of type `impl Iterator<Item = i32> + ?Sized` cannot be known at compilation time
+ --> $DIR/apit-unsized.rs:1:8
+ |
+LL | fn foo(_: impl Iterator<Item = i32> + ?Sized) {}
+ | ^ ---------------------------------- this type parameter needs to be `std::marker::Sized`
+ | |
+ | doesn't have a size known at compile-time
+ |
+ = help: unsized fn params are gated as an unstable feature
+help: consider removing the `?Sized` bound to make the type parameter `Sized`
+ |
+LL - fn foo(_: impl Iterator<Item = i32> + ?Sized) {}
+LL + fn foo(_: impl Iterator<Item = i32>) {}
+ |
+help: function arguments must have a statically known size, borrowed types always have a known size
+ |
+LL | fn foo(_: &impl Iterator<Item = i32> + ?Sized) {}
+ | +
+
+error[E0277]: the size for values of type `impl ?Sized` cannot be known at compilation time
+ --> $DIR/apit-unsized.rs:2:8
+ |
+LL | fn bar(_: impl ?Sized) {}
+ | ^ ----------- this type parameter needs to be `std::marker::Sized`
+ | |
+ | doesn't have a size known at compile-time
+ |
+ = help: unsized fn params are gated as an unstable feature
+help: consider replacing `?Sized` with `Sized`
+ |
+LL - fn bar(_: impl ?Sized) {}
+LL + fn bar(_: impl Sized) {}
+ |
+help: function arguments must have a statically known size, borrowed types always have a known size
+ |
+LL | fn bar(_: &impl ?Sized) {}
+ | +
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0277`.