🤖 Pick PR #50601 (Allow {} to narrow in same specia...) into release-4.8

src/compiler/checker.ts

@@ -25255,14 +25255,19 @@ namespace ts {
  assumeTrue = !assumeTrue;
  }
  const valueType = getTypeOfExpression(value);
- if ((type.flags & TypeFlags.Unknown) && assumeTrue && (operator === SyntaxKind.EqualsEqualsEqualsToken || operator === SyntaxKind.ExclamationEqualsEqualsToken)) {
+ if (((type.flags & TypeFlags.Unknown) || isEmptyAnonymousObjectType(type) && !(valueType.flags & TypeFlags.Nullable)) &&
+ assumeTrue &&
+ (operator === SyntaxKind.EqualsEqualsEqualsToken || operator === SyntaxKind.ExclamationEqualsEqualsToken)
+ ) {
  if (valueType.flags & (TypeFlags.Primitive | TypeFlags.NonPrimitive)) {
  return valueType;
  }
  if (valueType.flags & TypeFlags.Object) {
  return nonPrimitiveType;
  }
- return type;
+ if (type.flags & TypeFlags.Unknown) {
+ return type;
+ }
  }
  if (valueType.flags & TypeFlags.Nullable) {
  if (!strictNullChecks) {

tests/baselines/reference/emptyAnonymousObjectNarrowing(strictnullchecks=false).js

@@ -0,0 +1,139 @@
+//// [emptyAnonymousObjectNarrowing.ts]
+declare let nonNull: {};
+if (nonNull === "foo") {
+ nonNull;
+}
+else {
+ nonNull;
+}
+
+declare let obj: { a: string };
+if (nonNull === obj) {
+ nonNull;
+}
+else {
+ nonNull;
+}
+
+function f1<T>(x: T) {
+ if (nonNull === x) {
+ nonNull;
+ }
+ else {
+ nonNull;
+ }
+}
+
+function f2<T extends object>(x: T) {
+ if (nonNull === x) {
+ nonNull;
+ }
+ else {
+ nonNull;
+ }
+}
+
+declare let union: "xyz" | { a: string } | undefined;
+if (nonNull === union) {
+ nonNull;
+}
+else {
+ nonNull;
+}
+
+if (nonNull === undefined) {
+ nonNull;
+}
+else {
+ nonNull;
+}
+
+if (nonNull === null) {
+ nonNull;
+}
+else {
+ nonNull;
+}
+
+if (nonNull == undefined) {
+ nonNull;
+}
+else {
+ nonNull;
+}
+
+// Repro from #50567
+const foo = (value: unknown): string => {
+ if (!value) {
+ return 'foo';
+ }
+ if (value === 'xyz') {
+ return value; // Type '{}' is not assignable to type 'string'.
+ }
+ return '';
+};
+
+
+//// [emptyAnonymousObjectNarrowing.js]
+if (nonNull === "foo") {
+ nonNull;
+}
+else {
+ nonNull;
+}
+if (nonNull === obj) {
+ nonNull;
+}
+else {
+ nonNull;
+}
+function f1(x) {
+ if (nonNull === x) {
+ nonNull;
+ }
+ else {
+ nonNull;
+ }
+}
+function f2(x) {
+ if (nonNull === x) {
+ nonNull;
+ }
+ else {
+ nonNull;
+ }
+}
+if (nonNull === union) {
+ nonNull;
+}
+else {
+ nonNull;
+}
+if (nonNull === undefined) {
+ nonNull;
+}
+else {
+ nonNull;
+}
+if (nonNull === null) {
+ nonNull;
+}
+else {
+ nonNull;
+}
+if (nonNull == undefined) {
+ nonNull;
+}
+else {
+ nonNull;
+}
+// Repro from #50567
+var foo = function (value) {
+ if (!value) {
+ return 'foo';
+ }
+ if (value === 'xyz') {
+ return value; // Type '{}' is not assignable to type 'string'.
+ }
+ return '';
+};

tests/baselines/reference/emptyAnonymousObjectNarrowing(strictnullchecks=false).symbols

@@ -0,0 +1,139 @@
+=== tests/cases/compiler/emptyAnonymousObjectNarrowing.ts ===
+declare let nonNull: {};
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+
+if (nonNull === "foo") {
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+}
+else {
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+}
+
+declare let obj: { a: string };
+>obj : Symbol(obj, Decl(emptyAnonymousObjectNarrowing.ts, 8, 11))
+>a : Symbol(a, Decl(emptyAnonymousObjectNarrowing.ts, 8, 18))
+
+if (nonNull === obj) {
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+>obj : Symbol(obj, Decl(emptyAnonymousObjectNarrowing.ts, 8, 11))
+
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+}
+else {
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+}
+
+function f1<T>(x: T) {
+>f1 : Symbol(f1, Decl(emptyAnonymousObjectNarrowing.ts, 14, 1))
+>T : Symbol(T, Decl(emptyAnonymousObjectNarrowing.ts, 16, 12))
+>x : Symbol(x, Decl(emptyAnonymousObjectNarrowing.ts, 16, 15))
+>T : Symbol(T, Decl(emptyAnonymousObjectNarrowing.ts, 16, 12))
+
+ if (nonNull === x) {
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+>x : Symbol(x, Decl(emptyAnonymousObjectNarrowing.ts, 16, 15))
+
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+ }
+ else {
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+ }
+}
+
+function f2<T extends object>(x: T) {
+>f2 : Symbol(f2, Decl(emptyAnonymousObjectNarrowing.ts, 23, 1))
+>T : Symbol(T, Decl(emptyAnonymousObjectNarrowing.ts, 25, 12))
+>x : Symbol(x, Decl(emptyAnonymousObjectNarrowing.ts, 25, 30))
+>T : Symbol(T, Decl(emptyAnonymousObjectNarrowing.ts, 25, 12))
+
+ if (nonNull === x) {
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+>x : Symbol(x, Decl(emptyAnonymousObjectNarrowing.ts, 25, 30))
+
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+ }
+ else {
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+ }
+}
+
+declare let union: "xyz" | { a: string } | undefined;
+>union : Symbol(union, Decl(emptyAnonymousObjectNarrowing.ts, 34, 11))
+>a : Symbol(a, Decl(emptyAnonymousObjectNarrowing.ts, 34, 28))
+
+if (nonNull === union) {
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+>union : Symbol(union, Decl(emptyAnonymousObjectNarrowing.ts, 34, 11))
+
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+}
+else {
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+}
+
+if (nonNull === undefined) {
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+>undefined : Symbol(undefined)
+
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+}
+else {
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+}
+
+if (nonNull === null) {
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+}
+else {
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+}
+
+if (nonNull == undefined) {
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+>undefined : Symbol(undefined)
+
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+}
+else {
+ nonNull;
+>nonNull : Symbol(nonNull, Decl(emptyAnonymousObjectNarrowing.ts, 0, 11))
+}
+
+// Repro from #50567
+const foo = (value: unknown): string => {
+>foo : Symbol(foo, Decl(emptyAnonymousObjectNarrowing.ts, 64, 5))
+>value : Symbol(value, Decl(emptyAnonymousObjectNarrowing.ts, 64, 13))
+
+ if (!value) {
+>value : Symbol(value, Decl(emptyAnonymousObjectNarrowing.ts, 64, 13))
+
+ return 'foo';
+ }
+ if (value === 'xyz') {
+>value : Symbol(value, Decl(emptyAnonymousObjectNarrowing.ts, 64, 13))
+
+ return value; // Type '{}' is not assignable to type 'string'.
+>value : Symbol(value, Decl(emptyAnonymousObjectNarrowing.ts, 64, 13))
+ }
+ return '';
+};
+