Merge branch 'master' into symbolWriter2

Conflicts:	tests/baselines/reference/APISample_compile.types	tests/baselines/reference/APISample_linter.types	tests/baselines/reference/APISample_transform.types	tests/baselines/reference/APISample_watcher.types

Author: CyrusNajmabadi

src/compiler/checker.ts

@@ -4016,6 +4016,7 @@ module ts {
  if (source === numberType && target.flags & TypeFlags.Enum) return Ternary.True;
  }
  }
+ let saveErrorInfo = errorInfo;
  if (source.flags & TypeFlags.Union || target.flags & TypeFlags.Union) {
  if (relation === identityRelation) {
  if (source.flags & TypeFlags.Union && target.flags & TypeFlags.Union) {
@@ -4054,25 +4055,34 @@ module ts {
  return result;
  }
  }
- else {
- let saveErrorInfo = errorInfo;
- if (source.flags & TypeFlags.Reference && target.flags & TypeFlags.Reference && (<TypeReference>source).target === (<TypeReference>target).target) {
- // We have type references to same target type, see if relationship holds for all type arguments
- if (result = typesRelatedTo((<TypeReference>source).typeArguments, (<TypeReference>target).typeArguments, reportErrors)) {
- return result;
- }
+ else if (source.flags & TypeFlags.Reference && target.flags & TypeFlags.Reference && (<TypeReference>source).target === (<TypeReference>target).target) {
+ // We have type references to same target type, see if relationship holds for all type arguments
+ if (result = typesRelatedTo((<TypeReference>source).typeArguments, (<TypeReference>target).typeArguments, reportErrors)) {
+ return result;
  }
- // Even if relationship doesn't hold for type arguments, it may hold in a structural comparison
- // Report structural errors only if we haven't reported any errors yet
- let reportStructuralErrors = reportErrors && errorInfo === saveErrorInfo;
- // identity relation does not use apparent type
- let sourceOrApparentType = relation === identityRelation ? source : getApparentType(source);
- if (sourceOrApparentType.flags & TypeFlags.ObjectType && target.flags & TypeFlags.ObjectType &&
- (result = objectTypeRelatedTo(sourceOrApparentType, <ObjectType>target, reportStructuralErrors))) {
+ }
+
+ // Even if relationship doesn't hold for unions, type parameters, or generic type references,
+ // it may hold in a structural comparison.
+ // Report structural errors only if we haven't reported any errors yet
+ let reportStructuralErrors = reportErrors && errorInfo === saveErrorInfo;
+ // identity relation does not use apparent type
+ let sourceOrApparentType = relation === identityRelation ? source : getApparentType(source);
+ if (sourceOrApparentType.flags & TypeFlags.ObjectType && target.flags & TypeFlags.ObjectType) {
+ if (result = objectTypeRelatedTo(sourceOrApparentType, <ObjectType>target, reportStructuralErrors)) {
  errorInfo = saveErrorInfo;
  return result;
  }
  }
+ else if (source.flags & TypeFlags.TypeParameter && sourceOrApparentType.flags & TypeFlags.Union) {
+ // We clear the errors first because the following check often gives a better error than
+ // the union comparison above if it is applicable.
+ errorInfo = saveErrorInfo;
+ if (result = isRelatedTo(sourceOrApparentType, target, reportErrors)) {
+ return result;
+ }
+ }
+
  if (reportErrors) {
  headMessage = headMessage || Diagnostics.Type_0_is_not_assignable_to_type_1;
  let sourceType = typeToString(source);
@@ -12943,6 +12953,11 @@ module ts {
  }
  }
 
+ function isEvalOrArgumentsIdentifier(node: Node): boolean {
+ return node.kind === SyntaxKind.Identifier &&
+ ((<Identifier>node).text === "eval" || (<Identifier>node).text === "arguments");
+ }
+
  function checkGrammarConstructorTypeParameters(node: ConstructorDeclaration) {
  if (node.typeParameters) {
  return grammarErrorAtPos(getSourceFileOfNode(node), node.typeParameters.pos, node.typeParameters.end - node.typeParameters.pos, Diagnostics.Type_parameters_cannot_appear_on_a_constructor_declaration);