Fix remove parentheses bugs (#32284)

* Add tests to catch bugs

* Change analyzer to fix two bugs

* Add test to make sure parentheses will be remove when conditional expression used as rhs, change the loop in ParenthesesExpressionExtension to break properly

src/EditorFeatures/CSharpTest/RemoveUnnecessaryParentheses/RemoveUnnecessaryParenthesesTests.cs

@@ -2227,6 +2227,57 @@ void M(int x)
     {
         var v = x+$$(+x);
     }
+}", new TestParameters(options: RemoveAllUnnecessaryParentheses));
+        }
+
+        [WorkItem(31103, "https://github.com/dotnet/roslyn/issues/31103")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryParentheses)]
+        public async Task TestMissingForConditionalRefAsLeftHandSideValue()
+        {
+            await TestMissingAsync(
+@"class Bar
+{
+    void Foo(bool cond, double a, double b)
+    {
+        [||](cond ? ref a : ref b) = 6.67e-11;
+    }
+}", new TestParameters(options: RemoveAllUnnecessaryParentheses));
+        }
+
+        [WorkItem(31103, "https://github.com/dotnet/roslyn/issues/31103")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryParentheses)]
+        public async Task TestConditionalExpressionAsRightHandSideValue()
+        {
+            await TestInRegularAndScript1Async(
+@"class Bar
+{
+    void Foo(bool cond, double a, double b)
+    {
+        double c = $$(cond ? a : b);
+    }
+}",
+@"class Bar
+{
+    void Foo(bool cond, double a, double b)
+    {
+        double c = cond ? a : b;
+    }
+}",
+parameters: new TestParameters(options: RemoveAllUnnecessaryParentheses));
+        }
+
+        [WorkItem(32085, "https://github.com/dotnet/roslyn/issues/32085")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryParentheses)]
+        public async Task TestMissingForNestedConditionalExpressionInLambda()
+        {
+            await TestMissingAsync(
+@"class Bar
+{
+    void Test(bool a)
+    {
+        Func<int, string> lambda =
+            number => (number + $""{ ($$a ? ""foo"" : ""bar"") }"");
+    }
 }", new TestParameters(options: RemoveAllUnnecessaryParentheses));
         }
     }

src/Workspaces/CSharp/Portable/Extensions/ParenthesizedExpressionSyntaxExtensions.cs

@@ -255,6 +255,14 @@ public static bool CanRemoveParentheses(this ParenthesizedExpressionSyntax node,
                 }
             }
 
+            // (condition ? ref a : ref b ) = SomeValue, parenthesis can't be removed for when conditional expression appears at left
+            // This syntax is only allowed since C# 7.2
+            if (expression.IsKind(SyntaxKind.ConditionalExpression) &&
+                node.IsLeftSideOfAnyAssignExpression())
+            {
+                return false;
+            }
+
             // Operator precedence cases:
             // - If the parent is not an expression, do not remove parentheses
             // - Otherwise, parentheses may be removed if doing so does not change operator associations.
@@ -270,13 +278,15 @@ private static bool RemovalMayIntroduceInterpolationAmbiguity(ParenthesizedExpre
             InterpolationSyntax interpolation = null;
             foreach (var ancestor in node.Parent.AncestorsAndSelf())
             {
-                switch (ancestor.Kind())
+                if (ancestor.IsKind(SyntaxKind.ParenthesizedExpression))
                 {
-                    case SyntaxKind.ParenthesizedExpression:
-                        return false;
-                    case SyntaxKind.Interpolation:
-                        interpolation = (InterpolationSyntax)ancestor;
-                        break;
+                    return false;
+                }
+
+                if (ancestor.IsKind(SyntaxKind.Interpolation))
+                {
+                    interpolation = (InterpolationSyntax)ancestor;
+                    break;
                 }
             }