Add handling of comments between assignment (withoyt let) lhs and rhs

Author: davidBar-On

src/formatting/expr.rs

@@ -1898,16 +1898,22 @@ fn rewrite_assignment(
     op: Option<&ast::BinOp>,
     shape: Shape,
 ) -> Option<String> {
-    let operator_str = match op {
-        Some(op) => context.snippet(op.span),
-        None => "=",
+    let span_hi = rhs.span.lo();
+    let (operator_str, span_lo) = match op {
+        Some(op) => (context.snippet(op.span), op.span.hi()),
+        None => {
+            let lo = lhs.span.hi();
+            let offset = context.snippet(mk_sp(lo, span_hi)).find_uncommented("=")? + 1;
+            ("=", lo + BytePos(offset as u32))
+        }
     };
 
     // 1 = space between lhs and operator.
     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 between_span = mk_sp(span_lo, span_hi);
+    rewrite_assign_rhs_with_span(context, lhs_str, rhs, shape, between_span)
 }
 
 /// Controls where to put the rhs.
@@ -1933,6 +1939,26 @@ pub(crate) fn rewrite_assign_rhs<S: Into<String>, R: Rewrite>(
     rewrite_assign_rhs_with(context, lhs, ex, shape, RhsTactics::Default)
 }
 
+// The left hand side must contain everything up to, and including, the
+// assignment operator.
+pub(crate) fn rewrite_assign_rhs_with_span<S: Into<String>, R: Rewrite>(
+    context: &RewriteContext<'_>,
+    lhs: S,
+    ex: &R,
+    shape: Shape,
+    between_span: Span,
+) -> Option<String> {
+    rewrite_assign_rhs_with_comments(
+        context,
+        lhs,
+        ex,
+        shape,
+        RhsTactics::Default,
+        between_span,
+        true,
+    )
+}
+
 pub(crate) fn rewrite_assign_rhs_expr<R: Rewrite>(
     context: &RewriteContext<'_>,
     lhs: &str,

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

@@ -0,0 +1,48 @@
+// "=" 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;
+    }
+    
+    // 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;
+    }
+    

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

@@ -0,0 +1,59 @@
+// "=" 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;
+}
+
+// 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;
+}