Merge pull request microsoft#25342 from ajafff/factory-leftmost-expression

 getLeftmostExpression: handle AsExpression and NonNullExpression

Author: DanielRosenwasser

src/compiler/factory.ts

@@ -4354,19 +4354,17 @@ namespace ts {
                 case SyntaxKind.ConditionalExpression:
                     node = (<ConditionalExpression>node).condition;
                     continue;
-
                 case SyntaxKind.CallExpression:
                     if (stopAtCallExpressions) {
                         return node;
                     }
                     // falls through
+                case SyntaxKind.AsExpression:
                 case SyntaxKind.ElementAccessExpression:
                 case SyntaxKind.PropertyAccessExpression:
-                    node = (<CallExpression | PropertyAccessExpression | ElementAccessExpression>node).expression;
-                    continue;
-
+                case SyntaxKind.NonNullExpression:
                 case SyntaxKind.PartiallyEmittedExpression:
-                    node = (<PartiallyEmittedExpression>node).expression;
+                    node = (<CallExpression | PropertyAccessExpression | ElementAccessExpression | AsExpression | NonNullExpression | PartiallyEmittedExpression>node).expression;
                     continue;
             }
 

src/testRunner/tsconfig.json

@@ -39,7 +39,7 @@
         "unittests/extractTestHelpers.ts",
         "unittests/tsserverProjectSystem.ts",
         "unittests/typingsInstaller.ts",
-        
+
         "unittests/asserts.ts",
         "unittests/base64.ts",
         "unittests/builder.ts",
@@ -54,6 +54,7 @@
         "unittests/extractConstants.ts",
         "unittests/extractFunctions.ts",
         "unittests/extractRanges.ts",
+        "unittests/factory.ts",
         "unittests/hostNewLineSupport.ts",
         "unittests/incrementalParser.ts",
         "unittests/initializeTSConfig.ts",

src/testRunner/unittests/factory.ts

@@ -0,0 +1,24 @@
+namespace ts {
+    describe("FactoryAPI", () => {
+        describe("createArrowFunction", () => {
+            it("parenthesizes concise body if necessary", () => {
+                function checkBody(body: ConciseBody) {
+                    const node = createArrowFunction(
+                        /*modifiers*/ undefined,
+                        /*typeParameters*/ undefined,
+                        [],
+                        /*type*/ undefined,
+                        /*equalsGreaterThanToken*/ undefined,
+                        body,
+                    );
+                    assert.strictEqual(node.body.kind, SyntaxKind.ParenthesizedExpression);
+                }
+
+                checkBody(createObjectLiteral());
+                checkBody(createPropertyAccess(createObjectLiteral(), "prop"));
+                checkBody(createAsExpression(createPropertyAccess(createObjectLiteral(), "prop"), createTypeReferenceNode("T", /*typeArguments*/ undefined)));
+                checkBody(createNonNullExpression(createPropertyAccess(createObjectLiteral(), "prop")));
+            });
+        });
+    });
+}