Fixed comment formatting issue between assignment operator and rhs (#4440)

* Fixed comment formatting issue between assignment

* rewrite_rhs_with_comments method

* Add more tests

* Added more test cases and optimized

* Removed extra new lines

* Removed accidentally pushed tmp file

Author: whizsid

Diff for: src/formatting/expr.rs

@@ -1985,6 +1985,32 @@ pub(crate) fn rewrite_assign_rhs_with<S: Into<String>, R: Rewrite>(
     Some(lhs + &rhs)
 }
 
+pub(crate) fn rewrite_assign_rhs_with_comments<S: Into<String>, R: Rewrite>(
+    context: &RewriteContext<'_>,
+    lhs: S,
+    ex: &R,
+    shape: Shape,
+    rhs_tactics: RhsTactics,
+    between_span: Span,
+    allow_extend: bool,
+) -> Option<String> {
+    let lhs = lhs.into();
+    let contains_comment = contains_comment(context.snippet(between_span));
+    let shape = if contains_comment {
+        shape.block_left(context.config.tab_spaces())?
+    } else {
+        shape
+    };
+    let rhs = rewrite_assign_rhs_expr(context, &lhs, ex, shape, rhs_tactics)?;
+
+    if contains_comment {
+        let rhs = rhs.trim_start();
+        combine_strs_with_missing_comments(context, &lhs, &rhs, between_span, shape, allow_extend)
+    } else {
+        Some(lhs + &rhs)
+    }
+}
+
 fn choose_rhs<R: Rewrite>(
     context: &RewriteContext<'_>,
     expr: &R,

Diff for: src/formatting/items.rs

@@ -19,7 +19,7 @@ use crate::formatting::{
     },
     expr::{
         is_empty_block, is_simple_block_stmt, rewrite_assign_rhs, rewrite_assign_rhs_expr,
-        rewrite_assign_rhs_with, RhsTactics,
+        rewrite_assign_rhs_with, rewrite_assign_rhs_with_comments, RhsTactics,
     },
     lists::{definitive_tactic, itemize_list, write_list, ListFormatting, Separator},
     macros::{rewrite_macro, MacroPosition},
@@ -1878,14 +1878,22 @@ fn rewrite_static(
     };
 
     if let Some(expr) = static_parts.expr_opt {
+        let comments_lo = context.snippet_provider.span_after(static_parts.span, "=");
+        let expr_lo = expr.span.lo();
+        let comments_span = mk_sp(comments_lo, expr_lo);
+
         let lhs = format!("{}{} =", prefix, ty_str);
+
         // 1 = ;
         let remaining_width = context.budget(offset.block_indent + 1);
-        rewrite_assign_rhs(
+        rewrite_assign_rhs_with_comments(
             context,
             &lhs,
             &**expr,
             Shape::legacy(remaining_width, offset.block_only()),
+            RhsTactics::Default,
+            comments_span,
+            true,
         )
         .and_then(|res| recover_comment_removed(res, static_parts.span, context))
         .or_else(|| {

Diff for: tests/source/issue-4427.rs

@@ -0,0 +1,31 @@
+const A: usize = 
+  // Some constant
+    2;
+
+const B: usize =   
+/* constant */
+3;
+
+const C :   usize   
+      = /* foo */5;
+
+const D: usize =    // baz
+/*    Some constant */
+            /* ba */
+ {  3  
+ // foo   
+    };
+const E:   usize=             /* foo */5;
+const F: usize =
+{
+        7
+    };
+const G: usize = /* foooooooooooooooooooooooooooooooooooooooooooooooooooooooo0000000000000000xx00 */ 5;
+                  const H: usize = /* asdfasdf */ match G > 1 {
+                    true => 1,
+                    false => 3,
+                };
+            
+                pub static FOO_BAR: Vec<u8> =    //f
+                {
+                    vec![]};

Diff for: tests/target/issue-4427.rs

@@ -0,0 +1,30 @@
+const A: usize =
+    // Some constant
+    2;
+
+const B: usize =
+    /* constant */
+    3;
+
+const C: usize = /* foo */ 5;
+
+const D: usize = // baz
+    /*    Some constant */
+    /* ba */
+    {
+        3
+        // foo
+    };
+const E: usize = /* foo */ 5;
+const F: usize = { 7 };
+const G: usize =
+    /* foooooooooooooooooooooooooooooooooooooooooooooooooooooooo0000000000000000xx00 */
+    5;
+const H: usize = /* asdfasdf */
+    match G > 1 {
+        true => 1,
+        false => 3,
+    };
+
+pub static FOO_BAR: Vec<u8> = //f
+    { vec![] };