From ead2c4f1222c7c9023f02bf6dceaa49eb987c716 Mon Sep 17 00:00:00 2001
From: Marcel Hellwig <github@cookiesoft.de>
Date: Thu, 7 Jul 2022 12:24:17 +0200
Subject: [PATCH] fix incorrect suggestion for maybe trait bounds

---
 clippy_lints/src/trait_bounds.rs          | 19 ++++++++++++++-----
 tests/ui/type_repetition_in_bounds.rs     | 12 ++++++++++++
 tests/ui/type_repetition_in_bounds.stderr | 18 +++++++++++++++++-
 3 files changed, 43 insertions(+), 6 deletions(-)

diff --git a/clippy_lints/src/trait_bounds.rs b/clippy_lints/src/trait_bounds.rs
index 76b739c48f1..2741179074b 100644
--- a/clippy_lints/src/trait_bounds.rs
+++ b/clippy_lints/src/trait_bounds.rs
@@ -9,12 +9,12 @@ use rustc_data_structures::unhash::UnhashMap;
 use rustc_errors::Applicability;
 use rustc_hir::def::Res;
 use rustc_hir::{
-    GenericBound, Generics, Item, ItemKind, Node, Path, PathSegment, PredicateOrigin, QPath, TraitItem, Ty, TyKind,
-    WherePredicate,
+    GenericBound, Generics, Item, ItemKind, Node, Path, PathSegment, PredicateOrigin, QPath, TraitBoundModifier,
+    TraitItem, Ty, TyKind, WherePredicate,
 };
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
-use rustc_span::Span;
+use rustc_span::{BytePos, Span};
 
 declare_clippy_lint! {
     /// ### What it does
@@ -242,8 +242,17 @@ fn check_trait_bound_duplication(cx: &LateContext<'_>, gen: &'_ Generics<'_>) {
 }
 
 fn get_trait_info_from_bound<'a>(bound: &'a GenericBound<'_>) -> Option<(Res, &'a [PathSegment<'a>], Span)> {
-    if let GenericBound::Trait(t, _) = bound {
-        Some((t.trait_ref.path.res, t.trait_ref.path.segments, t.span))
+    if let GenericBound::Trait(t, tbm) = bound {
+        let trait_path = t.trait_ref.path;
+        let trait_span = {
+            let path_span = trait_path.span;
+            if let TraitBoundModifier::Maybe = tbm {
+                path_span.with_lo(path_span.lo() - BytePos(1)) // include the `?`
+            } else {
+                path_span
+            }
+        };
+        Some((trait_path.res, trait_path.segments, trait_span))
     } else {
         None
     }
diff --git a/tests/ui/type_repetition_in_bounds.rs b/tests/ui/type_repetition_in_bounds.rs
index d11432f9046..2eca1f4701c 100644
--- a/tests/ui/type_repetition_in_bounds.rs
+++ b/tests/ui/type_repetition_in_bounds.rs
@@ -79,6 +79,18 @@ where
     u: U,
 }
 
+// Check for the `?` in `?Sized`
+pub fn f<T: ?Sized>()
+where
+    T: Clone,
+{
+}
+pub fn g<T: Clone>()
+where
+    T: ?Sized,
+{
+}
+
 // This should not lint
 fn impl_trait(_: impl AsRef<str>, _: impl AsRef<str>) {}
 
diff --git a/tests/ui/type_repetition_in_bounds.stderr b/tests/ui/type_repetition_in_bounds.stderr
index 148c19c7d07..1d88714814d 100644
--- a/tests/ui/type_repetition_in_bounds.stderr
+++ b/tests/ui/type_repetition_in_bounds.stderr
@@ -19,5 +19,21 @@ LL |     Self: Copy + Default + Ord,
    |
    = help: consider combining the bounds: `Self: Clone + Copy + Default + Ord`
 
-error: aborting due to 2 previous errors
+error: this type has already been used as a bound predicate
+  --> $DIR/type_repetition_in_bounds.rs:85:5
+   |
+LL |     T: Clone,
+   |     ^^^^^^^^
+   |
+   = help: consider combining the bounds: `T: ?Sized + Clone`
+
+error: this type has already been used as a bound predicate
+  --> $DIR/type_repetition_in_bounds.rs:90:5
+   |
+LL |     T: ?Sized,
+   |     ^^^^^^^^^
+   |
+   = help: consider combining the bounds: `T: Clone + ?Sized`
+
+error: aborting due to 4 previous errors