fix(linter): panic in no-else-return (#6648)

closes #6636

crates/oxc_linter/src/rules/eslint/no_else_return.rs

@@ -263,8 +263,14 @@ fn left_offset_for_whitespace(ctx: &LintContext, position: u32) -> u32 {
         return position;
     }
 
-    let chars = ctx.source_text()[..(position as usize)].chars().rev();
-    let offset = chars.take_while(|c| c.is_whitespace()).count();
+    let mut offset = 0;
+    for c in ctx.source_text()[..(position as usize)].chars().rev() {
+        if !c.is_whitespace() {
+            break;
+        }
+        offset += c.len_utf8();
+    }
+
     debug_assert!(offset < u32::MAX as usize);
     offset as u32
 }
@@ -423,6 +429,7 @@ fn test() {
     ];
 
     let fail = vec![
+        ("if(0)return;else r", None),
         ("function foo1() { if (true) { return x; } else { return y; } }", None),
 ("function foo2() { if (true) { var x = bar; return x; } else { var y = baz; return y; } }", None),
 ("function foo3() { if (true) return x; else return y; }", None),
@@ -514,6 +521,7 @@ fn test() {
     ];
 
     let fix = vec![
+        ("if(0)return;else r", "if(0)return; r", None),
         ("function foo1() { if (true) { return x; } else { return y; } }", "function foo1() { if (true) { return x; } return y; }", None),
         ("function foo1() { if(true){ return x; }else{ return y; } }", "function foo1() { if(true){ return x; } return y; }", None),
 ("function foo2() { if (true) { var x = bar; return x; } else { var y = baz; return y; } }", "function foo2() { if (true) { var x = bar; return x; } var y = baz; return y; }", None),

crates/oxc_linter/src/snapshots/no_else_return.snap

@@ -1,6 +1,15 @@
 ---
 source: crates/oxc_linter/src/tester.rs
 ---
+  ⚠ eslint(no-else-return): Unnecessary 'else' after 'return'.
+   ╭─[no_else_return.tsx:1:6]
+ 1 │ if(0)return;else r
+   ·      ───┬─────┬──
+   ·         │     ╰── Making this `else` block unnecessary.
+   ·         ╰── This consequent block always returns,
+   ╰────
+  help: Remove the `else` block, moving its contents outside of the `if` statement.
+
   ⚠ eslint(no-else-return): Unnecessary 'else' after 'return'.
    ╭─[no_else_return.tsx:1:31]
  1 │ function foo1() { if (true) { return x; } else { return y; } }