Introduce HasTypeArguments matcher

refaster-support/src/main/java/tech/picnic/errorprone/refaster/matchers/HasTypeArguments.java

@@ -0,0 +1,38 @@
+package tech.picnic.errorprone.refaster.matchers;
+
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.matchers.Matcher;
+import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.MethodInvocationTree;
+import com.sun.source.tree.NewClassTree;
+import com.sun.source.tree.ParameterizedTypeTree;
+import com.sun.source.tree.Tree;
+
+/** A matcher of expressions with type arguments. */
+public final class HasTypeArguments implements Matcher<ExpressionTree> {
+  private static final long serialVersionUID = 1L;
+
+  /** Instantiates a new {@link HasTypeArguments} instance. */
+  public HasTypeArguments() {}
+
+  @Override
+  public boolean matches(ExpressionTree tree, VisitorState state) {
+    switch (tree.getKind()) {
+      case METHOD_INVOCATION:
+        return !((MethodInvocationTree) tree).getTypeArguments().isEmpty();
+      case NEW_CLASS:
+        NewClassTree classTree = (NewClassTree) tree;
+        if (!classTree.getTypeArguments().isEmpty()) {
+          return true;
+        }
+
+        if (classTree.getIdentifier().getKind() != Tree.Kind.PARAMETERIZED_TYPE) {
+          return false;
+        }
+
+        return !((ParameterizedTypeTree) classTree.getIdentifier()).getTypeArguments().isEmpty();
+      default:
+        return false;
+    }
+  }
+}

refaster-support/src/test/java/tech/picnic/errorprone/refaster/matchers/HasTypeArgumentsTest.java

@@ -0,0 +1,83 @@
+package tech.picnic.errorprone.refaster.matchers;
+
+import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
+
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.CompilationTestHelper;
+import com.google.errorprone.bugpatterns.BugChecker;
+import org.junit.jupiter.api.Test;
+
+final class HasTypeArgumentsTest {
+  @Test
+  void matches() {
+    CompilationTestHelper.newInstance(MatcherTestChecker.class, getClass())
+        .addSourceLines(
+            "A.java",
+            "import com.google.common.collect.ImmutableSet;",
+            "import java.util.ArrayList;",
+            "import java.util.List;",
+            "",
+            "class A {",
+            "  Object negative1() {",
+            "    return alwaysNull();",
+            "  }",
+            "",
+            "  Object negative2() {",
+            "    return new Object();",
+            "  }",
+            "",
+            "  List<Integer> negative3() {",
+            "    return new ArrayList<>();",
+            "  }",
+            "",
+            "  Foo negative4() {",
+            "    return new Foo(\"foo\");",
+            "  }",
+            "",
+            "  <E> ImmutableSet<E> positive1() {",
+            "    // BUG: Diagnostic contains:",
+            "    return ImmutableSet.<E>builder().build();",
+            "  }",
+            "",
+            "  <E> ImmutableSet<E> positive2() {",
+            "    // BUG: Diagnostic contains:",
+            "    return new ImmutableSet.Builder<E>().build();",
+            "  }",
+            "",
+            "  Foo positive3() {",
+            "    // BUG: Diagnostic contains:",
+            "    return new <List<Object>>Foo(List.of());",
+            "  }",
+            "",
+            "  private static <T> T alwaysNull() {",
+            "    return null;",
+            "  }",
+            "",
+            "  public static class Foo {",
+            "    private final Object value;",
+            "",
+            "    public Foo(Object value) {",
+            "      this.value = value;",
+            "    }",
+            "",
+            "    public <E extends List<Object>> Foo(E value) {",
+            "      this.value = value;",
+            "    }",
+            "  }",
+            "}")
+        .doTest();
+  }
+
+  /** A {@link BugChecker} that simply delegates to {@link HasTypeArguments}. */
+  @BugPattern(summary = "Flags expressions matched by `HasTypeArguments`", severity = ERROR)
+  public static final class MatcherTestChecker extends AbstractMatcherTestChecker {
+    private static final long serialVersionUID = 1L;
+
+    // XXX: This is a false positive reported by Checkstyle. See
+    // https://github.com/checkstyle/checkstyle/issues2/10161#issuecomment-1242732120.
+    @SuppressWarnings("RedundantModifier")
+    public MatcherTestChecker() {
+      super(new HasTypeArguments());
+    }
+  }
+}