Handle comments between trait generics and bounds

Author: davidBar-On

src/formatting/items.rs

@@ -1143,23 +1143,30 @@ pub(crate) fn format_trait(
             rewrite_generics(context, rewrite_ident(context, item.ident), generics, shape)?;
         result.push_str(&generics_str);
 
-        // FIXME(#2055): rustfmt fails to format when there are comments between trait bounds.
+        // FIXME(#2055): rustfmt fails to format when there are comments within trait bounds.
         if !generic_bounds.is_empty() {
-            let ident_hi = context
-                .snippet_provider
-                .span_after(item.span, &item.ident.as_str());
+            let bound_lo = generic_bounds.first().unwrap().span().lo();
             let bound_hi = generic_bounds.last().unwrap().span().hi();
-            let snippet = context.snippet(mk_sp(ident_hi, bound_hi));
+            let snippet = context.snippet(mk_sp(bound_lo, bound_hi));
             if contains_comment(snippet) {
                 return None;
             }
 
-            result = rewrite_assign_rhs_with(
+            // Rewrite rhs and combine lhs with pre-bound comment
+            let ident_hi = context
+                .snippet_provider
+                .span_after(item.span, &item.ident.as_str());
+            let ident_hi = context
+                .snippet_provider
+                .span_after(mk_sp(ident_hi, item.span.hi()), ":");
+            result = rewrite_assign_rhs_with_comments(
                 context,
                 result + ":",
                 generic_bounds,
                 shape,
                 RhsTactics::ForceNextLineWithoutIndent,
+                mk_sp(ident_hi, bound_lo),
+                true,
             )?;
         }
 
@@ -1199,6 +1206,8 @@ pub(crate) fn format_trait(
         }
         let pre_block_span = if !generics.where_clause.predicates.is_empty() {
             mk_sp(generics.where_clause.span.hi(), item.span.hi())
+        } else if !generic_bounds.is_empty() {
+            mk_sp(generic_bounds.last().unwrap().span().hi(), item.span.hi())
         } else {
             item.span
         };

tests/source/lhs-to-rhs-bewteen-comments/trait.rs

@@ -0,0 +1,52 @@
+// Based on issue #2055:
+pub trait A {}
+pub trait B {}
+pub trait C {}
+pub trait Foo1:
+A + C
++ B
+{}
+pub trait Foo2:
+// A and C
+A + C
++ B
+{}
+pub trait Foo3:
+/* A and C */
+A + C
++ B
+{}
+pub trait Foo4:// A and C
+A + C
++ B
+{}
+pub trait Foo5:/* A and C */
+A + C
++ B
+{}
+pub trait Foo6:/* A and C */A + C    + B{}
+
+// Other cases
+trait Person {
+fn name(&self) -> String;
+}
+trait Student:/* comment1 */Person/* comment2 */{
+fn university(&self) -> String;
+}
+trait Programmer/* comment1 */{
+fn fav_language(&self) -> String;
+}
+trait/* comment1 */CompSciStudent1:/* comment2 */Programmer + Student/* comment3 */{
+fn git_username(&self) -> String;
+}
+trait/* comment1 */CompSciStudent2:/* comment2 Longggggggggggggggggggggggggggggggggggggggggggggggggg */Programmer + Student/* comment3 */{
+fn git_username(&self) -> String;
+}
+trait/* comment1 */CompSciStudent3:// comment2
+Programmer + Student/* comment3 */{
+fn git_username(&self) -> String;
+}
+trait/* comment1 */CompSciStudent4:// comment2 Longgggggggggggggggggggggggggggggggggggggggggggggggggg
+Programmer + Student/* comment3 */{
+fn git_username(&self) -> String;
+}

tests/target/lhs-to-rhs-bewteen-comments/trait.rs

@@ -0,0 +1,51 @@
+// Based on issue #2055:
+pub trait A {}
+pub trait B {}
+pub trait C {}
+pub trait Foo1: A + C + B {}
+pub trait Foo2:
+    // A and C
+    A + C + B
+{
+}
+pub trait Foo3:
+    /* A and C */
+    A + C + B
+{
+}
+pub trait Foo4: // A and C
+    A + C + B
+{
+}
+pub trait Foo5: /* A and C */ A + C + B {}
+pub trait Foo6: /* A and C */ A + C + B {}
+
+// Other cases
+trait Person {
+    fn name(&self) -> String;
+}
+trait Student: /* comment1 */ Person /* comment2 */ {
+    fn university(&self) -> String;
+}
+trait Programmer /* comment1 */ {
+    fn fav_language(&self) -> String;
+}
+trait CompSciStudent1: /* comment2 */ Programmer + Student /* comment3 */ {
+    fn git_username(&self) -> String;
+}
+trait CompSciStudent2:
+    /* comment2 Longggggggggggggggggggggggggggggggggggggggggggggggggg */
+    Programmer + Student /* comment3 */
+{
+    fn git_username(&self) -> String;
+}
+trait CompSciStudent3: // comment2
+    Programmer + Student /* comment3 */
+{
+    fn git_username(&self) -> String;
+}
+trait CompSciStudent4: // comment2 Longgggggggggggggggggggggggggggggggggggggggggggggggggg
+    Programmer + Student /* comment3 */
+{
+    fn git_username(&self) -> String;
+}