fix infinite recursion in template type checking

PiperOrigin-RevId: 615186462

Author: sjamesr

src/com/google/javascript/rhino/jstype/SubtypeChecker.java

@@ -263,6 +263,16 @@ private boolean isSubtypeHelper(JSType subtype, JSType supertype) {
   private boolean isObjectSubtypeHelper(ObjectType subtype, ObjectType supertype) {
     TemplateTypeMap subtypeParams = subtype.getTemplateTypeMap();
     TemplateTypeMap supertypeParams = supertype.getTemplateTypeMap();
+    boolean subAndSuperAreSameBaseType = false;
+    if (subtype.isTemplatizedType() && supertype.isTemplatizedType()) {
+      TemplatizedType templatizedSubType = subtype.toMaybeTemplatizedType();
+      TemplatizedType templatizedSuperType = supertype.toMaybeTemplatizedType();
+      ObjectType superTypeReferencedType = templatizedSuperType.getReferencedType();
+      ObjectType subTypeReferencedType = templatizedSubType.getReferencedType();
+      if (subTypeReferencedType.equals(superTypeReferencedType)) {
+        subAndSuperAreSameBaseType = true;
+      }
+    }
     boolean bivarantMatch = false;
 
     /*
@@ -284,7 +294,9 @@ private boolean isObjectSubtypeHelper(ObjectType subtype, ObjectType supertype)
       bivarantMatch = true;
     }
 
-    if (this.isUsingStructuralTyping && supertype.isStructuralType()) {
+    if (!subAndSuperAreSameBaseType
+        && this.isUsingStructuralTyping
+        && supertype.isStructuralType()) {
       /*
        * Do this before considering templatization in general.
        *
@@ -293,7 +305,7 @@ private boolean isObjectSubtypeHelper(ObjectType subtype, ObjectType supertype)
        */
       return this.isStructuralSubtypeHelper(
           subtype, supertype, PropertyOptionality.VOIDABLE_PROPS_ARE_OPTIONAL);
-    } else if (supertype.isRecordType()) {
+    } else if (!subAndSuperAreSameBaseType && supertype.isRecordType()) {
       /*
        * Anonymous record types are always considered structurally when supertypes.
        *

test/com/google/javascript/jscomp/integration/AdvancedOptimizationsIntegrationTest.java

@@ -216,11 +216,6 @@ public void testFoldSpread() {
 
   @Test
   public void testBug303058080() {
-    // TODO: b/303058080 - Actually fix the problem this test records.
-    // The problem is a timeout, so as-written this test doesn't actually trigger the timeout.
-    // See the comment below for how to modify this test case to cause the timeout for
-    // investigation.
-
     // Avoid including the transpilation library
     useNoninjectingCompiler = true;
     CompilerOptions options = createCompilerOptions();
@@ -259,11 +254,11 @@ public void testBug303058080() {
                     "var Bar = function() {};",
                     "",
                     "/**",
-                    " * @return {!Foo<?>}", // Change `?` to `T` to trigger the timeout
+                    " * @return {!Foo<T>}",
                     " */",
                     "Bar.prototype.flatten = function() {};")
                 .buildExternsFile("externs.js"));
-    // The timeout happens while processing the externs, so there's no need to have any input
+    // The timeout happened while processing the externs, so there's no need to have any input
     // code.
     test(options, "", "");
   }