From 9c8bf51f142090de5c30341b744a7d7456bc309e Mon Sep 17 00:00:00 2001 From: Deep Majumder Date: Tue, 13 Dec 2022 15:57:48 +0530 Subject: [PATCH 1/2] Remove invalid case for mutable borrow suggestion If we have a call such as `foo(&mut buf)` and after reference collapsing the type is inferred as `&T` where-as the required type is `&mut T`, don't suggest `foo(&mut mut buf)`. This is wrong syntactically and the issue lies elsewhere, not in the borrow. Fixes #105645 --- .../src/traits/error_reporting/suggestions.rs | 11 +++++++++++ src/test/ui/suggestions/issue-105645.rs | 8 ++++++++ src/test/ui/suggestions/issue-105645.stderr | 18 ++++++++++++++++++ 3 files changed, 37 insertions(+) create mode 100644 src/test/ui/suggestions/issue-105645.rs create mode 100644 src/test/ui/suggestions/issue-105645.stderr diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs index 40c8102547112..2323161039a2b 100644 --- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs +++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs @@ -1368,6 +1368,17 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> { .source_map() .span_take_while(span, |c| c.is_whitespace() || *c == '&'); if points_at_arg && mutability.is_not() && refs_number > 0 { + // If we have a call like foo(&mut buf), then don't suggest foo(&mut mut buf) + if "mut" + == snippet + .chars() + .filter(|c| !c.is_whitespace()) + .skip(refs_number) + .take(3) + .collect::() + { + return; + } err.span_suggestion_verbose( sp, "consider changing this borrow's mutability", diff --git a/src/test/ui/suggestions/issue-105645.rs b/src/test/ui/suggestions/issue-105645.rs new file mode 100644 index 0000000000000..681ce1c6e37a6 --- /dev/null +++ b/src/test/ui/suggestions/issue-105645.rs @@ -0,0 +1,8 @@ +fn main() { + let mut buf = [0u8; 50]; + let mut bref = buf.as_slice(); + foo(&mut bref); + //~^ ERROR 4:9: 4:18: the trait bound `&[u8]: std::io::Write` is not satisfied [E0277] +} + +fn foo(_: &mut impl std::io::Write) {} diff --git a/src/test/ui/suggestions/issue-105645.stderr b/src/test/ui/suggestions/issue-105645.stderr new file mode 100644 index 0000000000000..895f5ffd1e1c7 --- /dev/null +++ b/src/test/ui/suggestions/issue-105645.stderr @@ -0,0 +1,18 @@ +error[E0277]: the trait bound `&[u8]: std::io::Write` is not satisfied + --> $DIR/issue-105645.rs:4:9 + | +LL | foo(&mut bref); + | --- ^^^^^^^^^ the trait `std::io::Write` is not implemented for `&[u8]` + | | + | required by a bound introduced by this call + | + = help: the trait `std::io::Write` is implemented for `&mut [u8]` +note: required by a bound in `foo` + --> $DIR/issue-105645.rs:8:21 + | +LL | fn foo(_: &mut impl std::io::Write) {} + | ^^^^^^^^^^^^^^ required by this bound in `foo` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`. From afefbb66c3abea2e9b3acacddf7516b24c2bbeb8 Mon Sep 17 00:00:00 2001 From: Deep Majumder Date: Wed, 14 Dec 2022 10:30:44 +0530 Subject: [PATCH 2/2] Clean up mut keyword check --- .../src/traits/error_reporting/suggestions.rs | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs index 2323161039a2b..554cab3fb6cb4 100644 --- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs +++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs @@ -1369,13 +1369,9 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> { .span_take_while(span, |c| c.is_whitespace() || *c == '&'); if points_at_arg && mutability.is_not() && refs_number > 0 { // If we have a call like foo(&mut buf), then don't suggest foo(&mut mut buf) - if "mut" - == snippet - .chars() - .filter(|c| !c.is_whitespace()) - .skip(refs_number) - .take(3) - .collect::() + if snippet + .trim_start_matches(|c: char| c.is_whitespace() || c == '&') + .starts_with("mut") { return; }