Don't crash when trying to qualify ambiguous simple names

Discovered while validating 2.4.0 release (#1639)

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=313496085

Author: cushon

check_api/src/main/java/com/google/errorprone/fixes/SuggestedFixes.java

@@ -381,7 +381,9 @@ public static String qualifyType(VisitorState state, SuggestedFix.Builder fix, S
     // Check if the simple name is already visible.
     String simpleName = Iterables.getLast(components);
     Symbol simpleNameSymbol = FindIdentifiers.findIdent(simpleName, state, KindSelector.VAL_TYP);
-    if (simpleNameSymbol != null && simpleNameSymbol.getQualifiedName().contentEquals(typeName)) {
+    if (simpleNameSymbol != null
+        && !simpleNameSymbol.getKind().equals(ElementKind.OTHER)
+        && simpleNameSymbol.getQualifiedName().contentEquals(typeName)) {
       return simpleName;
     }
 

core/src/test/java/com/google/errorprone/bugpatterns/NonCanonicalTypeTest.java

@@ -126,4 +126,29 @@ public void negative() {
             "}")
         .doTest();
   }
+
+  @Test
+  public void qualifiedName_ambiguous() {
+    compilationHelper
+        .addSourceLines(
+            "Test.java",
+            "interface A {",
+            "  interface N {}",
+            "}",
+            "interface B extends A {}",
+            "class C implements D {}",
+            "interface E extends D {",
+            "  interface N extends D.N {}",
+            "}",
+            "interface D {",
+            "  interface N {}",
+            "}",
+            "class Test extends C implements E {",
+            "  // BUG: Diagnostic contains: A.N",
+            "  private B.N f() {",
+            "    return null;",
+            "  }",
+            "}")
+        .doTest();
+  }
 }