Add missing parens in type serializer (#3743)

Author: weswigham

internal/transformers/tstransforms/typeserializer.go

@@ -260,7 +260,7 @@ func (s *metadataSerializer) serializeUnionOrIntersectionConstituents(types []*a
 			return s.f.NewIdentifier("Object") // Reduce to `any` in a union or intersection
 		}
 
-		if !s.strictNullChecks && (ast.IsLiteralTypeNode(typeNode) && typeNode.AsLiteralTypeNode().Literal.Kind == ast.KindNullKeyword) || typeNode.Kind == ast.KindUndefinedKeyword {
+		if !s.strictNullChecks && ((ast.IsLiteralTypeNode(typeNode) && typeNode.AsLiteralTypeNode().Literal.Kind == ast.KindNullKeyword) || typeNode.Kind == ast.KindUndefinedKeyword) {
 			continue // Elide null and undefined from unions for metadata, just like what we did prior to the implementation of strict null checks
 		}
 

testdata/baselines/reference/submodule/compiler/metadataOfUnionWithNull(strictnullchecks=true).js

@@ -70,7 +70,7 @@ __decorate([
 ], B.prototype, "y", void 0);
 __decorate([
     PropDeco,
-    __metadata("design:type", String)
+    __metadata("design:type", Object)
 ], B.prototype, "z", void 0);
 __decorate([
     PropDeco,

testdata/baselines/reference/submodule/compiler/metadataReferencedWithinFilteredUnion(strictnullchecks=true,target=es2015).js

@@ -54,7 +54,7 @@ class Class2 {
 exports.Class2 = Class2;
 __decorate([
     decorate,
-    __metadata("design:type", Class1_1.Class1),
+    __metadata("design:type", Object),
     __metadata("design:paramtypes", [])
 ], Class2.prototype, "maybeProp", null);
 __decorate([

testdata/baselines/reference/submoduleTriaged/compiler/metadataOfUnionWithNull(strictnullchecks=true).js.diff

@@ -153,11 +153,6 @@ conformance/moduleExportsElementAccessAssignment.js.diff
 ## https://github.com/microsoft/typescript-go/issues/3547
 conformance/typeFromPropertyAssignment39.js.diff
 
-# Decorator metadata reflects stable union type ordering
-## https://github.com/microsoft/typescript-go/issues/3548
-compiler/metadataOfUnionWithNull(strictnullchecks=true).js.diff
-compiler/metadataReferencedWithinFilteredUnion(strictnullchecks=true,target=es2015).js.diff
-
 # Missing generic type arguments no longer auto-filled with any (produces TS2314 errors)
 ## https://github.com/microsoft/typescript-go/issues/3549
 conformance/jsDeclarationsMissingGenerics(target=es2015).js.diff