Handle comments between trait generics and bounds

Author: davidBar-On

src/formatting/items.rs

@@ -1131,30 +1131,42 @@ pub(crate) fn format_trait(
         );
         result.push_str(&header);
 
+        // FIXME: rustfmt fails to format when there are comments before the ident.
+        if contains_comment(context.snippet(mk_sp(item.span.lo(), generics.span.lo()))) {
+            return None;
+        }
+
         let body_lo = context.snippet_provider.span_after(item.span, "{");
 
         let shape = Shape::indented(offset, context.config).offset_left(result.len())?;
         let generics_str =
             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,
             )?;
         }
 
@@ -1194,6 +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 +1,70 @@
+// 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;
+}
+/*comment1*/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:/* comment1 */Programmer + Student/* comment2 */{
+fn git_username(&self) -> String;
+}
+trait CompSciStudent2:/* comment1 Longggggggggggggggggggggggggggggggggggggggggggggggggg */Programmer + Student/* comment2 */{
+fn git_username(&self) -> String;
+}
+trait CompSciStudent3:// comment1
+Programmer + Student/* comment2 */{
+fn git_username(&self) -> String;
+}
+trait CompSciStudent4:// comment1 Longgggggggggggggggggggggggggggggggggggggggggggggggggg
+Programmer + Student/* comment2 */{
+fn git_username(&self) -> String;
+}
+
+// Comment before Ident
+trait /* comment1 */ Person {
+    fn fav_language(&self) -> String;
+}
+trait // comment1
+Person {
+    fn fav_language(&self) -> String;
+}
+trait /* comment 1 */ Programmer /* comment2 */ {
+    fn fav_language(&self) -> String;
+}
+trait /* comment1 */ CompSciStudent1: /* comment2 */ Programmer + Student /* comment3 */ {
+    fn git_username(&self) -> String;
+}

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

@@ -0,0 +1,70 @@
+// 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;
+}
+/*comment1*/
+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: /* comment1 */ Programmer + Student /* comment2 */ {
+    fn git_username(&self) -> String;
+}
+trait CompSciStudent2:
+    /* comment1 Longggggggggggggggggggggggggggggggggggggggggggggggggg */
+    Programmer + Student /* comment2 */
+{
+    fn git_username(&self) -> String;
+}
+trait CompSciStudent3: // comment1
+    Programmer + Student /* comment2 */
+{
+    fn git_username(&self) -> String;
+}
+trait CompSciStudent4: // comment1 Longgggggggggggggggggggggggggggggggggggggggggggggggggg
+    Programmer + Student /* comment2 */
+{
+    fn git_username(&self) -> String;
+}
+
+// Comment before Ident
+trait /* comment1 */ Person {
+    fn fav_language(&self) -> String;
+}
+trait // comment1
+Person {
+    fn fav_language(&self) -> String;
+}
+trait /* comment 1 */ Programmer /* comment2 */ {
+    fn fav_language(&self) -> String;
+}
+trait /* comment1 */ CompSciStudent1: /* comment2 */ Programmer + Student /* comment3 */ {
+    fn git_username(&self) -> String;
+}