Don't register types mismatch if actual type satisfies any of required union's alternates

PiperOrigin-RevId: 512008241

Author: Closure Team

src/com/google/javascript/jscomp/TypeMismatch.java

@@ -70,6 +70,13 @@ void registerMismatch(Node location, JSType found, JSType required) {
       if (found.isSubtypeOf(required) || required.isSubtypeOf(found)) {
         return;
       }
+      if (required.isUnionType()) {
+        for (JSType requiredAltType : required.toMaybeUnionType().getAlternates()) {
+          if (requiredAltType.isSubtypeOf(found)) {
+            return;
+          }
+        }
+      }
 
       if (bothAreNotTemplateTypes(found, required)) {
         this.mismatches.add(TypeMismatch.create(found, required, location));

test/com/google/javascript/jscomp/TypeValidatorTest.java

@@ -334,6 +334,16 @@ public void testSubclass() {
     this.assertThatRecordedMismatches().isEmpty();
   }
 
+  @Test
+  public void testUnionsMismatch() {
+    testWarning(
+        "/** @param {number|string} x */\n"
+            + "function f(x) {}\n"
+            + "f(/** @type {boolean|string} */ ('a'));",
+        TYPE_MISMATCH_WARNING);
+    this.assertThatRecordedMismatches().isEmpty();
+  }
+
   @Test
   public void testModuloNullUndef1() {
     testSame(