Fix supertrait wrapping when within max_width

src/items.rs

@@ -1190,15 +1190,14 @@ pub(crate) fn format_trait(
         if contains_comment(snippet) {
             return Err(RewriteError::Unknown);
         }
+        let bounds_shape = if context.config.style_edition() >= StyleEdition::Edition2027 {
+            Shape::indented(offset, context.config)
+        } else {
+            Shape::indented(offset, context.config).sub_width(result.len(), ident.span)?
+        };
 
-        result = rewrite_assign_rhs_with(
-            context,
-            result + ":",
-            bounds,
-            shape,
-            &RhsAssignKind::Bounds,
-            RhsTactics::ForceNextLineWithoutIndent,
-        )?;
+        let lhs = result + ":";
+        result = rewrite_assign_rhs(context, lhs, bounds, &RhsAssignKind::Bounds, bounds_shape)?;
     }
 
     // Rewrite where-clause.

tests/source/issue-6809/supertraits.rs

@@ -0,0 +1,24 @@
+// rustfmt-max_width: 50
+
+// line below is 30 chars
+pub(super) unsafe trait A: B {
+    fn foo();
+}
+
+// line below is 36 chars
+pub unsafe trait Trait2: A + B + C {
+    fn foo();
+}
+
+// line below is 43 chars
+pub trait TraitThree: Super1 + Super2 + X {
+    fn foo();
+}
+
+// line below is 47 chars
+trait TraitNumberFour: Super1 + Super2 + Abcd {
+    fn foo();
+}
+
+// line below is correctly not wrapped
+pub const THIS_LINE_IS_50_CHARS: usize = 12345678;

tests/source/issue-6809/supertraits_max_width_100.rs

@@ -0,0 +1,25 @@
+// rustfmt-style_edition: 2027
+// rustfmt-max_width: 100
+
+// line below is 80 chars
+pub(super) unsafe trait ALetsMakeThisLineLongerByExactlyFiftyCharacters1234: B {
+    fn foo();
+}
+
+// line below is 86 chars
+pub unsafe trait Trait2LetsMakeThisLineLongerByExactlyFiftyCharacters1234: A + B + C {
+    fn foo();
+}
+
+// line below is 93 chars
+pub trait TraitThreeLetsMakeThisLineLongerByExactlyFiftyCharacters1234: Super1 + Super2 + X {
+    fn foo();
+}
+
+// line below is 97 chars
+trait TraitNumberFourLetsMakeThisLineLongerByExactlyFiftyCharacters1234: Super1 + Super2 + Abcd {
+    fn foo();
+}
+
+// line below is correctly not wrapped
+pub const THIS_LINE_IS_100_CHARS: &str = "12345678901234567890123456789012345678901234567890123456";

tests/target/issue-6809/supertraits.rs

@@ -0,0 +1,24 @@
+// rustfmt-max_width: 50
+
+// line below is 30 chars
+pub(super) unsafe trait A: B {
+    fn foo();
+}
+
+// line below is 36 chars
+pub unsafe trait Trait2: A + B + C {
+    fn foo();
+}
+
+// line below is 43 chars
+pub trait TraitThree: Super1 + Super2 + X {
+    fn foo();
+}
+
+// line below is 47 chars
+trait TraitNumberFour: Super1 + Super2 + Abcd {
+    fn foo();
+}
+
+// line below is correctly not wrapped
+pub const THIS_LINE_IS_50_CHARS: usize = 12345678;

tests/target/issue-6809/supertraits_max_width_100.rs

@@ -0,0 +1,25 @@
+// rustfmt-style_edition: 2027
+// rustfmt-max_width: 100
+
+// line below is 80 chars
+pub(super) unsafe trait ALetsMakeThisLineLongerByExactlyFiftyCharacters1234: B {
+    fn foo();
+}
+
+// line below is 86 chars
+pub unsafe trait Trait2LetsMakeThisLineLongerByExactlyFiftyCharacters1234: A + B + C {
+    fn foo();
+}
+
+// line below is 93 chars
+pub trait TraitThreeLetsMakeThisLineLongerByExactlyFiftyCharacters1234: Super1 + Super2 + X {
+    fn foo();
+}
+
+// line below is 97 chars
+trait TraitNumberFourLetsMakeThisLineLongerByExactlyFiftyCharacters1234: Super1 + Super2 + Abcd {
+    fn foo();
+}
+
+// line below is correctly not wrapped
+pub const THIS_LINE_IS_100_CHARS: &str = "12345678901234567890123456789012345678901234567890123456";