Comments between assignment (without let) lhs and rhs handling

src/formatting/expr.rs

@@ -194,11 +194,11 @@ pub(crate) fn format_expr(
         ast::ExprKind::Path(ref qself, ref path) => {
             rewrite_path(context, PathContext::Expr, qself.as_ref(), path, shape)
         }
-        ast::ExprKind::Assign(ref lhs, ref rhs, _) => {
-            rewrite_assignment(context, lhs, rhs, None, shape)
+        ast::ExprKind::Assign(ref lhs, ref rhs, op_span) => {
+            rewrite_assignment(context, lhs, rhs, op_span, shape)
         }
         ast::ExprKind::AssignOp(ref op, ref lhs, ref rhs) => {
-            rewrite_assignment(context, lhs, rhs, Some(op), shape)
+            rewrite_assignment(context, lhs, rhs, op.span, shape)
         }
         ast::ExprKind::Continue(ref opt_label) => {
             let id_str = match *opt_label {
@@ -1895,19 +1895,24 @@ fn rewrite_assignment(
     context: &RewriteContext<'_>,
     lhs: &ast::Expr,
     rhs: &ast::Expr,
-    op: Option<&ast::BinOp>,
+    op_span: Span,
     shape: Shape,
 ) -> Option<String> {
-    let operator_str = match op {
-        Some(op) => context.snippet(op.span),
-        None => "=",
-    };
-
     // 1 = space between lhs and operator.
+    let operator_str = context.snippet(op_span);
     let lhs_shape = shape.sub_width(operator_str.len() + 1)?;
     let lhs_str = format!("{} {}", lhs.rewrite(context, lhs_shape)?, operator_str);
 
-    rewrite_assign_rhs(context, lhs_str, rhs, shape)
+    let comments_span = mk_sp(op_span.hi(), rhs.span.lo());
+    rewrite_assign_rhs_with_comments(
+        context,
+        lhs_str,
+        rhs,
+        shape,
+        RhsTactics::Default,
+        comments_span,
+        true,
+    )
 }
 
 /// Controls where to put the rhs.

tests/source/lhs-to-rhs-between-comments/assignment.rs

@@ -0,0 +1,76 @@
+// "=" Assignemnt
+fn main () {
+    let var = first;
+    var = second;
+    }
+    fn main () {
+    let var = /* Block comment */ first;
+    var = /* Block comment */ second;
+    }
+    fn main () {
+    let var = // Line comment
+    first;
+        var = // Line comment
+        second;
+    }
+    fn main () {
+    let var = /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ first;
+    var = /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ second;
+    }
+    fn main () {
+    let var = /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ first;
+    var = /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ second;
+    }
+    fn main () {
+    let var = /* Block comment line 1 
+    * Block comment line 2
+    * Block comment line 3 */ first;
+    var = /* Block comment line 1 
+    * Block comment line 2
+    * Block comment line 3 */ second;
+    var = /* Block comment line 1 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+    * Block comment line 2
+    * Block comment line 3 */ third;
+    var = /* Block comment line 1 
+    * Block comment line 2 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+    * Block comment line 3 */ forth;
+    }
+
+    // BinOp Assigment
+    fn main () {
+    let var = first;
+    var += second;
+    }
+    fn main () {
+    let var = /* Block comment */ first;
+    var -= /* Block comment */ second;
+    }
+    fn main () {
+    let var = // Line comment
+    first;
+    var *= // Line comment
+    second;
+    }
+    fn main () {
+    let var = /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ first;
+    var /= /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ second;
+    }
+    fn main () {
+    let var = /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ first;
+    var /= /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ second;
+    }
+    fn main () {
+    let var = /* Block comment line 1 
+    * Block comment line 2
+    * Block comment line 3 */ first;
+    var += /* Block comment line 1 
+    * Block comment line 2
+    * Block comment line 3 */ second;
+    var -= /* Block comment line 1 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+    * Block comment line 2
+    * Block comment line 3 */ third;
+    var *= /* Block comment line 1 
+    * Block comment line 2 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+    * Block comment line 3 */ forth;
+    }
+

tests/target/lhs-to-rhs-between-comments/assignment.rs

@@ -0,0 +1,97 @@
+// "=" Assignemnt
+fn main() {
+    let var = first;
+    var = second;
+}
+fn main() {
+    let var = /* Block comment */ first;
+    var = /* Block comment */ second;
+}
+fn main() {
+    let var = // Line comment
+        first;
+    var = // Line comment
+        second;
+}
+fn main() {
+    let var = /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggg */
+        first;
+    var = /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */
+        second;
+}
+fn main() {
+    let var =
+        /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */
+        first;
+    var =
+        /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */
+        second;
+}
+fn main() {
+    let var = /* Block comment line 1
+         * Block comment line 2
+         * Block comment line 3 */
+        first;
+    var = /* Block comment line 1
+         * Block comment line 2
+         * Block comment line 3 */
+        second;
+    var =
+        /* Block comment line 1 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+         * Block comment line 2
+         * Block comment line 3 */
+        third;
+    var = /* Block comment line 1
+         * Block comment line 2 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+         * Block comment line 3 */
+        forth;
+}
+
+// BinOp Assigment
+fn main() {
+    let var = first;
+    var += second;
+}
+fn main() {
+    let var = /* Block comment */ first;
+    var -= /* Block comment */ second;
+}
+fn main() {
+    let var = // Line comment
+        first;
+    var *= // Line comment
+        second;
+}
+fn main() {
+    let var = /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggg */
+        first;
+    var /= /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */
+        second;
+}
+fn main() {
+    let var =
+        /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */
+        first;
+    var /=
+        /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */
+        second;
+}
+fn main() {
+    let var = /* Block comment line 1
+         * Block comment line 2
+         * Block comment line 3 */
+        first;
+    var += /* Block comment line 1
+         * Block comment line 2
+         * Block comment line 3 */
+        second;
+    var -=
+        /* Block comment line 1 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+         * Block comment line 2
+         * Block comment line 3 */
+        third;
+    var *= /* Block comment line 1
+         * Block comment line 2 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+         * Block comment line 3 */
+        forth;
+}