Detect doubled unnecessary_parenthesis, but allow ternary and equality

lib/src/rules/unnecessary_parenthesis.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 
 import '../analyzer.dart';
@@ -100,11 +101,22 @@ class _Visitor extends SimpleAstVisitor<void> {
       }
     }
 
-    if (parent is ParenthesizedExpression) {
+    // Directly wrapped into parentheses already - always report.
+    if (parent is ParenthesizedExpression ||
+        parent is InterpolationExpression ||
+        (parent is ArgumentList && parent.arguments.length == 1) ||
+        (parent is IfStatement && node == parent.condition) ||
+        (parent is WhileStatement && node == parent.condition) ||
+        (parent is IfElement && node == parent.condition)) {
       rule.reportLint(node);
       return;
     }
 
+    // `(foo ? bar : baz)` is OK.
+    if (expression is ConditionalExpression) {
+      return;
+    }
+
     // `a..b = (c..d)` is OK.
     if (expression is CascadeExpression ||
         node.thisOrAncestorMatching(
@@ -121,6 +133,18 @@ class _Visitor extends SimpleAstVisitor<void> {
       return;
     }
 
+    // `foo = (a == b)` is OK, `return (count != 0)` is OK.
+    if (expression is BinaryExpression &&
+        (expression.operator.type == TokenType.EQ_EQ ||
+            expression.operator.type == TokenType.BANG_EQ)) {
+      if (parent is AssignmentExpression ||
+          parent is VariableDeclaration ||
+          parent is ReturnStatement ||
+          parent is YieldStatement) {
+        return;
+      }
+    }
+
     if (parent is Expression) {
       if (parent is BinaryExpression) return;
       if (parent is ConditionalExpression) return;

test_data/rules/unnecessary_parenthesis.dart

@@ -116,8 +116,41 @@ main() async {
   List<String> list = <String>[];
   (list[list.length]).toString(); // LINT
 
+  print(!({"a": "b"}["a"]!.isEmpty)); // LINT
+
+  print((1 + 2)); // LINT
+
+  print((1 == 1 ? 2 : 3)); // LINT
+  print('a'.substring((1 == 1 ? 2 : 3), 4)); // OK
+  var a1 = (1 == 1 ? 2 : 3); // OK
+  print('${(1 == 1 ? 2 : 3)}'); // LINT
+  print([(1 == 1 ? 2 : 3)]); // OK
+
+  var a2 = (1 == 1); // OK
+  a2 = (1 == 1); // OK
+  a2 = (1 == 1) || "".isEmpty; // OK
+  var a3 = (1 + 1); // LINT
 }
 
+bool test() {
+  if ((1 == 1 ? true : false)) // LINT
+  {
+    return true;
+  } else if ((1 == 1 ? true : false)) // LINT
+  {
+    return false;
+  }
+  if ((1 == 1)) // LINT
+  {
+    return (1 != 1); // OK
+  } else {
+    return (1 > 1); // LINT
+  }
+}
+
+int test2() => (1 == 1 ? 2 : 3); // OK
+bool test3() => (1 == 1); // LINT
+
 Invocation? invocation() => null;
 
 m({p}) => null;