Add a suggested fix to TreeToString by searching for an available Vis…

…itorState.

(And move it to TreeToString to match the check name.)

RELNOTES: N/A

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=227496488

core/src/main/java/com/google/errorprone/bugpatterns/TreeToStringChecker.java → core/src/main/java/com/google/errorprone/bugpatterns/TreeToString.java

@@ -18,32 +18,39 @@
 
 import static com.google.errorprone.BugPattern.ProvidesFix.NO_FIX;
 import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.util.ASTHelpers.getReceiver;
+import static com.google.errorprone.util.ASTHelpers.isSubtype;
 
 import com.google.common.base.Optional;
 import com.google.errorprone.BugPattern;
 import com.google.errorprone.VisitorState;
 import com.google.errorprone.fixes.Fix;
+import com.google.errorprone.fixes.SuggestedFix;
 import com.google.errorprone.matchers.Matcher;
 import com.google.errorprone.matchers.Matchers;
 import com.google.errorprone.predicates.TypePredicate;
 import com.google.errorprone.predicates.TypePredicates;
 import com.google.errorprone.util.ASTHelpers;
+import com.google.errorprone.util.FindIdentifiers;
 import com.sun.source.tree.ClassTree;
 import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.MethodInvocationTree;
 import com.sun.source.tree.Tree;
 import com.sun.tools.javac.code.Type;
 
 /**
- * Flags com.sun.source.tree.Tree#toString usage in {@link BugChecker}s.
+ * Flags {@code com.sun.source.tree.Tree#toString} usage in {@link BugChecker}s.
  *
  * @author bhagwani@google.com (Sumit Bhagwani)
  */
 @BugPattern(
     name = "TreeToString",
-    summary = "Tree.toString shouldn't be used",
+    summary =
+        "Tree#toString shouldn't be used for Trees deriving from the code being "
+            + "compiled, as it discards whitespace and comments.",
     severity = WARNING,
     providesFix = NO_FIX)
-public class TreeToStringChecker extends AbstractToString {
+public class TreeToString extends AbstractToString {
 
   private static final Matcher<ClassTree> IS_BUGCHECKER =
       Matchers.isSubtypeOf("com.google.errorprone.bugpatterns.BugChecker");
@@ -61,7 +68,7 @@ private static boolean treeToStringInBugChecker(Type type, VisitorState state) {
 
   @Override
   protected TypePredicate typePredicate() {
-    return TreeToStringChecker::treeToStringInBugChecker;
+    return TreeToString::treeToStringInBugChecker;
   }
 
   @Override
@@ -71,11 +78,36 @@ protected Optional<String> descriptionMessageForDefaultMatch(Type type, VisitorS
 
   @Override
   protected Optional<Fix> implicitToStringFix(ExpressionTree tree, VisitorState state) {
-    return Optional.absent();
+    return fix(tree, tree, state);
   }
 
   @Override
   protected Optional<Fix> toStringFix(Tree parent, ExpressionTree tree, VisitorState state) {
-    return Optional.absent();
+    if (!(parent instanceof MethodInvocationTree)) {
+      return Optional.absent();
+    }
+    ExpressionTree receiver = getReceiver((ExpressionTree) parent);
+    if (receiver == null) {
+      return Optional.absent();
+    }
+    return fix(receiver, parent, state);
+  }
+
+  private static Optional<Fix> fix(Tree target, Tree replace, VisitorState state) {
+    return Optional.fromJavaUtil(
+        FindIdentifiers.findAllIdents(state).stream()
+            .filter(
+                s ->
+                    isSubtype(
+                        s.type,
+                        state.getTypeFromString("com.google.errorprone.VisitorState"),
+                        state))
+            .findFirst()
+            .map(
+                s ->
+                    SuggestedFix.replace(
+                        replace,
+                        String.format(
+                            "%s.getSourceForNode(%s)", s, state.getSourceForNode(target)))));
   }
 }

core/src/main/java/com/google/errorprone/scanner/BuiltInCheckerSuppliers.java

@@ -252,7 +252,7 @@
 import com.google.errorprone.bugpatterns.ThrowNull;
 import com.google.errorprone.bugpatterns.ThrowsUncheckedException;
 import com.google.errorprone.bugpatterns.ToStringReturnsNull;
-import com.google.errorprone.bugpatterns.TreeToStringChecker;
+import com.google.errorprone.bugpatterns.TreeToString;
 import com.google.errorprone.bugpatterns.TruthAssertExpected;
 import com.google.errorprone.bugpatterns.TruthConstantAsserts;
 import com.google.errorprone.bugpatterns.TruthSelfEquals;
@@ -686,7 +686,7 @@ public static ScannerSupplier errorChecks() {
           ThreeLetterTimeZoneID.class,
           TimeUnitConversionChecker.class,
           ToStringReturnsNull.class,
-          TreeToStringChecker.class,
+          TreeToString.class,
           TruthAssertExpected.class,
           TruthConstantAsserts.class,
           TruthIncompatibleType.class,

core/src/test/java/com/google/errorprone/bugpatterns/TreeToStringCheckerTest.java → core/src/test/java/com/google/errorprone/bugpatterns/TreeToStringTest.java

@@ -21,11 +21,11 @@
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
-/** Unit tests for {@link TreeToStringChecker}. */
+/** Unit tests for {@link TreeToString}. */
 @RunWith(JUnit4.class)
-public class TreeToStringCheckerTest {
+public class TreeToStringTest {
   private final CompilationTestHelper testHelper =
-      CompilationTestHelper.newInstance(TreeToStringChecker.class, getClass());
+      CompilationTestHelper.newInstance(TreeToString.class, getClass());
 
   @Test
   public void noMatch() {
@@ -70,7 +70,7 @@ public void matchInABugChecker() {
             "@BugPattern(name = \"Example\", summary = \"\", severity = SeverityLevel.ERROR)",
             "public class ExampleChecker extends BugChecker implements ClassTreeMatcher {",
             "  @Override public Description matchClass(ClassTree tree, VisitorState state) {",
-            "    // BUG: Diagnostic contains: TreeToString",
+            "    // BUG: Diagnostic contains: state.getSourceForNode(tree).contains",
             "    if (tree.toString().contains(\"match\")) {",
             "      return describeMatch(tree);",
             "    }",