`MoreTypes.isTypeOf` returns false for `ErrorType` rather than throwing.

Throwing `IllegalArgumentException` can mask the real source of a problem, or prevent code that would have handled the `ErrorType` from running. The `ErrorType` typically (maybe always) corresponds to an identifier in the source code, so it is in fact a class, just one that doesn't exist.

RELNOTES=MoreTypes.isTypeOf returns false for ErrorType rather than throwing.
PiperOrigin-RevId: 369464743

2 files changed, 21 insertions, 0 deletions

diff --git a/common/src/main/java/com/google/auto/common/MoreTypes.java b/common/src/main/java/com/google/auto/common/MoreTypes.java
index b84432f4..af433aa0 100644
--- a/common/src/main/java/com/google/auto/common/MoreTypes.java
+++ b/common/src/main/java/com/google/auto/common/MoreTypes.java
@@ -836,6 +836,11 @@ public final class MoreTypes {
     }
 
     @Override
+    public Boolean visitError(ErrorType errorType, Void p) {
+      return false;
+    }
+
+    @Override
     public Boolean visitPrimitive(PrimitiveType type, Void p) {
       switch (type.getKind()) {
         case BOOLEAN:
diff --git a/common/src/test/java/com/google/auto/common/MoreTypesTest.java b/common/src/test/java/com/google/auto/common/MoreTypesTest.java
index 3cd360db..ff33ffc1 100644
--- a/common/src/test/java/com/google/auto/common/MoreTypesTest.java
+++ b/common/src/test/java/com/google/auto/common/MoreTypesTest.java
@@ -18,6 +18,7 @@ package com.google.auto.common;
 import static com.google.common.truth.Truth.assertThat;
 import static javax.lang.model.type.TypeKind.NONE;
 import static javax.lang.model.type.TypeKind.VOID;
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.fail;
 
 import com.google.common.base.Function;
@@ -471,6 +472,21 @@ public class MoreTypesTest {
     }
   }
 
+  @Test
+  public void testIsTypeOf() {
+    Types types = compilationRule.getTypes();
+    PrimitiveType intType = types.getPrimitiveType(TypeKind.INT);
+    TypeMirror integerType = types.boxedClass(intType).asType();
+    WildcardType wildcardType = types.getWildcardType(null, null);
+    expect.that(MoreTypes.isTypeOf(int.class, intType)).isTrue();
+    expect.that(MoreTypes.isTypeOf(Integer.class, integerType)).isTrue();
+    expect.that(MoreTypes.isTypeOf(Integer.class, intType)).isFalse();
+    expect.that(MoreTypes.isTypeOf(int.class, integerType)).isFalse();
+    expect.that(MoreTypes.isTypeOf(Integer.class, FAKE_ERROR_TYPE)).isFalse();
+    assertThrows(
+        IllegalArgumentException.class, () -> MoreTypes.isTypeOf(Integer.class, wildcardType));
+  }
+
   // The type of every field here is such that casting to it provokes an "unchecked" warning.
   @SuppressWarnings("unused")
   private static class Unchecked<T> {