/**
 * Check for duplicate case labels in a switch statement Eg: switch (foo) { case 1: case 1: }
 *
 * <p>This is normally an indication of a programmer error.
 *
 * <p>Inspired by ESLint
 * (https://github.com/eslint/eslint/blob/master/lib/rules/no-duplicate-case.js)
 *
 * <p>TODO(moz): Move this into {@link CheckSuspiciousCode}.
 */
public final class CheckDuplicateCase extends AbstractPostOrderCallback
    implements HotSwapCompilerPass {
  public static final DiagnosticType DUPLICATE_CASE =
      DiagnosticType.warning("JSC_DUPLICATE_CASE", "Duplicate case in a switch statement.");

  private final AbstractCompiler compiler;

  public CheckDuplicateCase(AbstractCompiler compiler) {
    this.compiler = compiler;
  }

  @Override
  public void process(Node externs, Node root) {
    NodeTraversal.traverseEs6(compiler, root, this);
  }

  @Override
  public void hotSwapScript(Node scriptRoot, Node originalRoot) {
    NodeTraversal.traverseEs6(compiler, scriptRoot, this);
  }

  @Override
  public void visit(NodeTraversal t, Node n, Node parent) {
    if (n.isSwitch()) {
      Set<String> cases = new HashSet<>();
      for (Node curr = n.getSecondChild(); curr != null; curr = curr.getNext()) {
        String source = compiler.toSource(curr.getFirstChild());
        if (!cases.add(source)) {
          t.report(curr, DUPLICATE_CASE);
        }
      }
    }
  }
}
예제 #2
0
public final class MissingProvideException extends CompilationException.Single {

  private static final long serialVersionUID = 1L;

  private static final DiagnosticType MISSING_PROVIDE =
      DiagnosticType.error("PLOVR_MISSING_PROVIDE", "Missing provide for {0} in {1}");

  private final JsInput input;

  private final String missingProvide;

  // TODO(bolinfest): Get the line number and character offset where the
  // error occurred so it is possible to link to it.

  /**
   * @param input the file that contains the goog.require() call.
   * @param missingProvide the thing that was required.
   */
  MissingProvideException(JsInput input, String missingProvide) {
    super(String.format("Missing provide for %s in %s", missingProvide, input.getName()));
    this.input = input;
    this.missingProvide = missingProvide;
  }

  @Override
  public CompilationError createCompilationError() {
    final int lineno = -1;
    final int charno = -1;
    JSError jsError =
        JSError.make(
            getInput().getName(),
            lineno,
            charno,
            CheckLevel.ERROR,
            MISSING_PROVIDE,
            getMissingProvide(),
            getInput().getName());
    return new CompilationError(jsError);
  }

  public JsInput getInput() {
    return input;
  }

  public String getMissingProvide() {
    return missingProvide;
  }
}
/**
 * @author [email protected] (Ben Lickly)
 * @author [email protected] (Dimitris Vardoulakis)
 */
public final class JSTypeCreatorFromJSDoc {
  public static final DiagnosticType INVALID_GENERICS_INSTANTIATION =
      DiagnosticType.warning(
          "JSC_NTI_INVALID_GENERICS_INSTANTIATION",
          "Invalid generics instantiation for {0}.\n"
              + "Expected {1} type argument(s), but found {2}");

  public static final DiagnosticType EXTENDS_NON_OBJECT =
      DiagnosticType.warning("JSC_NTI_EXTENDS_NON_OBJECT", "{0} extends non-object type {1}.\n");

  public static final DiagnosticType EXTENDS_NOT_ON_CTOR_OR_INTERF =
      DiagnosticType.warning(
          "JSC_NTI_EXTENDS_NOT_ON_CTOR_OR_INTERF",
          "@extends used without @constructor or @interface for {0}.\n");

  public static final DiagnosticType INHERITANCE_CYCLE =
      DiagnosticType.warning(
          "JSC_NTI_INHERITANCE_CYCLE", "Cycle detected in inheritance chain of type {0}");

  public static final DiagnosticType DICT_IMPLEMENTS_INTERF =
      DiagnosticType.warning(
          "JSC_NTI_DICT_IMPLEMENTS_INTERF",
          "Class {0} is a dict. Dicts can't implement interfaces");

  public static final DiagnosticType IMPLEMENTS_WITHOUT_CONSTRUCTOR =
      DiagnosticType.warning(
          "JSC_NTI_IMPLEMENTS_WITHOUT_CONSTRUCTOR",
          "@implements used without @constructor or @interface for {0}");

  // Not part of ALL_DIAGNOSTICS because it should not be enabled with
  // --jscomp_error=newCheckTypes. It should only be enabled explicitly.
  public static final DiagnosticType CONFLICTING_SHAPE_TYPE =
      DiagnosticType.disabled(
          "JSC_NTI_CONFLICTING_SHAPE_TYPE",
          "{1} cannot extend this type; {0}s can only extend {0}s");

  public static final DiagnosticType CONFLICTING_EXTENDED_TYPE =
      DiagnosticType.warning(
          "JSC_NTI_CONFLICTING_EXTENDED_TYPE",
          "{1} cannot extend this type; {0}s can only extend {0}s");

  public static final DiagnosticType CONFLICTING_IMPLEMENTED_TYPE =
      DiagnosticType.warning(
          "JSC_NTI_CONFLICTING_IMPLEMENTED_TYPE",
          "{0} cannot implement this type; "
              + "an interface can only extend, but not implement interfaces");

  public static final DiagnosticType UNION_IS_UNINHABITABLE =
      DiagnosticType.warning(
          "JSC_NTI_UNION_IS_UNINHABITABLE",
          "Union of {0} with {1} would create an impossible type");

  public static final DiagnosticType NEW_EXPECTS_OBJECT_OR_TYPEVAR =
      DiagnosticType.warning(
          "JSC_NTI_NEW_EXPECTS_OBJECT_OR_TYPEVAR",
          "The \"new:\" annotation only accepts object types and type variables; " + "found {0}");

  public static final DiagnosticType BAD_ARRAY_TYPE_SYNTAX =
      DiagnosticType.warning(
          "JSC_NTI_BAD_ARRAY_TYPE_SYNTAX",
          "The [] type syntax is not supported. Please use Array.<T> instead");

  public static final DiagnosticType CANNOT_MAKE_TYPEVAR_NON_NULL =
      DiagnosticType.warning(
          "JSC_NTI_CANNOT_MAKE_TYPEVAR_NON_NULL",
          "Cannot use ! to restrict type variable type.\n"
              + "Prefer to make type argument non-nullable and add "
              + "null explicitly where needed (e.g. through ?T or T|null)");

  public static final DiagnosticType CIRCULAR_TYPEDEF_ENUM =
      DiagnosticType.warning(
          "JSC_NTI_CIRCULAR_TYPEDEF_ENUM", "Circular typedefs/enums are not allowed");

  public static final DiagnosticType ENUM_WITH_TYPEVARS =
      DiagnosticType.warning(
          "JSC_NTI_ENUM_WITH_TYPEVARS", "An enum type cannot include type variables");

  public static final DiagnosticType ENUM_IS_TOP =
      DiagnosticType.warning(
          "JSC_NTI_ENUM_IS_TOP",
          "An enum type cannot be *. " + "Use ? if you do not want the elements checked");

  // TODO(dimvar): This may prove to be too strict, may revisit.
  public static final DiagnosticType ENUM_IS_UNION =
      DiagnosticType.warning("JSC_NTI_ENUM_IS_UNION", "An enum type cannot be a union type");

  public static final DiagnosticType WRONG_PARAMETER_ORDER =
      DiagnosticType.warning(
          "JSC_NTI_WRONG_PARAMETER_ORDER",
          "Wrong parameter order: required parameters are first, " + "then optional, then varargs");

  public static final DiagnosticType IMPLEMENTS_NON_INTERFACE =
      DiagnosticType.warning(
          "JSC_NTI_IMPLEMENTS_NON_INTERFACE", "Cannot implement non-interface {0}");

  public static final DiagnosticType EXTENDS_NON_INTERFACE =
      DiagnosticType.warning("JSC_NTI_EXTENDS_NON_INTERFACE", "Cannot extend non-interface {0}");

  public static final DiagnosticType FUNCTION_WITH_NONFUNC_JSDOC =
      DiagnosticType.warning(
          "JSC_NTI_FUNCTION_WITH_NONFUNC_JSDOC",
          "The function is annotated with a non-function jsdoc. " + "Ignoring jsdoc");

  public static final DiagnosticType TEMPLATED_GETTER_SETTER =
      DiagnosticType.warning(
          "JSC_NTI_TEMPLATED_GETTER_SETTER", "@template can't be used with getters/setters");

  public static final DiagnosticType TWO_JSDOCS =
      DiagnosticType.warning("JSC_NTI_TWO_JSDOCS", "Found two JsDoc comments for {0}");

  public static final DiagnosticGroup ALL_DIAGNOSTICS =
      new DiagnosticGroup(
          BAD_ARRAY_TYPE_SYNTAX,
          CANNOT_MAKE_TYPEVAR_NON_NULL,
          CIRCULAR_TYPEDEF_ENUM,
          CONFLICTING_EXTENDED_TYPE,
          CONFLICTING_IMPLEMENTED_TYPE,
          DICT_IMPLEMENTS_INTERF,
          ENUM_IS_TOP,
          ENUM_IS_UNION,
          ENUM_WITH_TYPEVARS,
          EXTENDS_NON_INTERFACE,
          EXTENDS_NON_OBJECT,
          EXTENDS_NOT_ON_CTOR_OR_INTERF,
          FUNCTION_WITH_NONFUNC_JSDOC,
          IMPLEMENTS_NON_INTERFACE,
          IMPLEMENTS_WITHOUT_CONSTRUCTOR,
          INHERITANCE_CYCLE,
          INVALID_GENERICS_INSTANTIATION,
          NEW_EXPECTS_OBJECT_OR_TYPEVAR,
          TEMPLATED_GETTER_SETTER,
          TWO_JSDOCS,
          UNION_IS_UNINHABITABLE,
          WRONG_PARAMETER_ORDER);

  private final CodingConvention convention;
  private final UniqueNameGenerator nameGen;

  // Used to communicate state between methods when resolving enum types
  private int howmanyTypeVars = 0;

  /** Exception for when unrecognized type names are encountered */
  public static class UnknownTypeException extends Exception {
    UnknownTypeException(String cause) {
      super(cause);
    }
  }

  private Set<JSError> warnings = new LinkedHashSet<>();
  // Unknown type names indexed by JSDoc AST node at which they were found.
  private Map<Node, String> unknownTypeNames = new LinkedHashMap<>();

  public JSTypeCreatorFromJSDoc(CodingConvention convention, UniqueNameGenerator nameGen) {
    this.qmarkFunctionDeclared =
        new FunctionAndSlotType(
            null, FunctionTypeBuilder.qmarkFunctionBuilder().buildDeclaration());
    this.convention = convention;
    this.nameGen = nameGen;
  }

  private FunctionAndSlotType qmarkFunctionDeclared;
  private static final boolean NULLABLE_TYPES_BY_DEFAULT = true;

  public JSType maybeMakeNullable(JSType t) {
    if (NULLABLE_TYPES_BY_DEFAULT) {
      return JSType.join(JSType.NULL, t);
    }
    return t;
  }

  public JSType getDeclaredTypeOfNode(
      JSDocInfo jsdoc, RawNominalType ownerType, DeclaredTypeRegistry registry) {
    return getDeclaredTypeOfNode(
        jsdoc,
        registry,
        ownerType == null ? ImmutableList.<String>of() : ownerType.getTypeParameters());
  }

  private JSType getDeclaredTypeOfNode(
      JSDocInfo jsdoc, DeclaredTypeRegistry registry, ImmutableList<String> typeParameters) {
    if (jsdoc == null) {
      return null;
    }
    return getTypeFromJSTypeExpression(jsdoc.getType(), registry, typeParameters);
  }

  public Set<JSError> getWarnings() {
    return warnings;
  }

  public Map<Node, String> getUnknownTypesMap() {
    return unknownTypeNames;
  }

  private JSType getTypeFromJSTypeExpression(
      JSTypeExpression expr, DeclaredTypeRegistry registry, ImmutableList<String> typeParameters) {
    if (expr == null) {
      return null;
    }
    return getTypeFromComment(expr.getRoot(), registry, typeParameters);
  }

  // Very similar to JSTypeRegistry#createFromTypeNodesInternal
  // n is a jsdoc node, not an AST node; the same class (Node) is used for both
  private JSType getTypeFromComment(
      Node n, DeclaredTypeRegistry registry, ImmutableList<String> typeParameters) {
    try {
      return getTypeFromCommentHelper(n, registry, typeParameters);
    } catch (UnknownTypeException e) {
      return JSType.UNKNOWN;
    }
  }

  private JSType getMaybeTypeFromComment(
      Node n, DeclaredTypeRegistry registry, ImmutableList<String> typeParameters) {
    try {
      return getTypeFromCommentHelper(n, registry, typeParameters);
    } catch (UnknownTypeException e) {
      return null;
    }
  }

  private JSType getTypeFromCommentHelper(
      Node n, DeclaredTypeRegistry registry, ImmutableList<String> typeParameters)
      throws UnknownTypeException {
    Preconditions.checkNotNull(n);
    if (typeParameters == null) {
      typeParameters = ImmutableList.of();
    }
    switch (n.getType()) {
      case Token.LC:
        return getRecordTypeHelper(n, registry, typeParameters);
      case Token.EMPTY: // for function types that don't declare a return type
        return JSType.UNKNOWN;
      case Token.VOID:
        // TODO(dimvar): void can be represented in 2 ways: Token.VOID and a
        // Token.STRING whose getString() is "void".
        // Change jsdoc parsing to only have one representation.
        return JSType.UNDEFINED;
      case Token.LB:
        warnings.add(JSError.make(n, BAD_ARRAY_TYPE_SYNTAX));
        return JSType.UNKNOWN;
      case Token.STRING:
        return getNamedTypeHelper(n, registry, typeParameters);
      case Token.PIPE:
        {
          // The way JSType.join works, Subtype|Supertype is equal to Supertype,
          // so when programmers write un-normalized unions, we normalize them
          // silently. We may also want to warn.
          JSType union = JSType.BOTTOM;
          for (Node child = n.getFirstChild(); child != null; child = child.getNext()) {
            // TODO(dimvar): When the union has many things, we join and throw
            // away types, except the result of the last join. Very inefficient.
            // Consider optimizing.
            JSType nextType = getTypeFromCommentHelper(child, registry, typeParameters);
            if (nextType.isUnknown()) {
              return JSType.UNKNOWN;
            }
            JSType nextUnion = JSType.join(union, nextType);
            if (nextUnion.isBottom()) {
              warnings.add(
                  JSError.make(n, UNION_IS_UNINHABITABLE, nextType.toString(), union.toString()));
              return JSType.UNKNOWN;
            }
            union = nextUnion;
          }
          return union;
        }
      case Token.BANG:
        {
          JSType nullableType =
              getTypeFromCommentHelper(n.getFirstChild(), registry, typeParameters);
          if (nullableType.isTypeVariable()) {
            warnings.add(JSError.make(n, CANNOT_MAKE_TYPEVAR_NON_NULL));
          }
          return nullableType.removeType(JSType.NULL);
        }
      case Token.QMARK:
        {
          Node child = n.getFirstChild();
          if (child == null) {
            return JSType.UNKNOWN;
          } else {
            return JSType.join(
                JSType.NULL, getTypeFromCommentHelper(child, registry, typeParameters));
          }
        }
      case Token.STAR:
        return JSType.TOP;
      case Token.FUNCTION:
        return getFunTypeHelper(n, registry, typeParameters);
      default:
        throw new IllegalArgumentException(
            "Unsupported type exp: " + Token.name(n.getType()) + " " + n.toStringTree());
    }
  }

  // Looks at the type AST without evaluating it
  private boolean isUnionWithUndefined(Node n) {
    if (n == null || n.getType() != Token.PIPE) {
      return false;
    }
    for (Node child : n.children()) {
      if (child.getType() == Token.VOID
          || child.getType() == Token.STRING
              && (child.getString().equals("void") || child.getString().equals("undefined"))) {
        return true;
      }
    }
    return false;
  }

  private JSType getRecordTypeHelper(
      Node n, DeclaredTypeRegistry registry, ImmutableList<String> typeParameters)
      throws UnknownTypeException {
    Map<String, Property> props = new LinkedHashMap<>();
    for (Node propNode = n.getFirstFirstChild(); propNode != null; propNode = propNode.getNext()) {
      boolean isPropDeclared = propNode.getType() == Token.COLON;
      Node propNameNode = isPropDeclared ? propNode.getFirstChild() : propNode;
      String propName = propNameNode.getString();
      if (propName.startsWith("'") || propName.startsWith("\"")) {
        propName = propName.substring(1, propName.length() - 1);
      }
      JSType propType =
          !isPropDeclared
              ? JSType.UNKNOWN
              : getTypeFromCommentHelper(propNode.getLastChild(), registry, typeParameters);
      Property prop;
      if (propType.equals(JSType.UNDEFINED) || isUnionWithUndefined(propNode.getLastChild())) {
        prop = Property.makeOptional(null, propType, propType);
      } else {
        prop = Property.make(propType, propType);
      }
      props.put(propName, prop);
    }
    return JSType.fromObjectType(ObjectType.fromProperties(props));
  }

  private JSType getNamedTypeHelper(
      Node n, DeclaredTypeRegistry registry, ImmutableList<String> outerTypeParameters)
      throws UnknownTypeException {
    String typeName = n.getString();
    switch (typeName) {
      case "boolean":
        return JSType.BOOLEAN;
      case "null":
        return JSType.NULL;
      case "number":
        return JSType.NUMBER;
      case "string":
        return JSType.STRING;
      case "undefined":
      case "void":
        return JSType.UNDEFINED;
      case "Function":
        return maybeMakeNullable(registry.getCommonTypes().qmarkFunction());
      case "Object":
        // We don't generally handle parameterized Object<...>, but we want to
        // at least not warn about inexistent properties on it, so we type it
        // as @dict.
        return maybeMakeNullable(n.hasChildren() ? JSType.TOP_DICT : JSType.TOP_OBJECT);
      default:
        return lookupTypeByName(typeName, n, registry, outerTypeParameters);
    }
  }

  private JSType lookupTypeByName(
      String name, Node n, DeclaredTypeRegistry registry, ImmutableList<String> outerTypeParameters)
      throws UnknownTypeException {
    String tvar = UniqueNameGenerator.findGeneratedName(name, outerTypeParameters);
    if (tvar != null) {
      return JSType.fromTypeVar(tvar);
    }
    Declaration decl = registry.getDeclaration(QualifiedName.fromQualifiedString(name), true);
    if (decl == null) {
      unknownTypeNames.put(n, name);
      throw new UnknownTypeException("Unhandled type: " + name);
    }
    // It's either a typedef, an enum, a type variable or a nominal type
    if (decl.getTypedef() != null) {
      return getTypedefType(decl.getTypedef(), registry);
    }
    if (decl.getEnum() != null) {
      return getEnumPropType(decl.getEnum(), registry);
    }
    if (decl.isTypeVar()) {
      howmanyTypeVars++;
      return decl.getTypeOfSimpleDecl();
    }
    if (decl.getNominal() != null) {
      return getNominalTypeHelper(decl.getNominal(), n, registry, outerTypeParameters);
    }
    return JSType.UNKNOWN;
  }

  private JSType getTypedefType(Typedef td, DeclaredTypeRegistry registry) {
    resolveTypedef(td, registry);
    return td.getType();
  }

  public void resolveTypedef(Typedef td, DeclaredTypeRegistry registry) {
    Preconditions.checkState(
        td != null,
        "getTypedef should only be " + "called when we know that the typedef is defined");
    if (td.isResolved()) {
      return;
    }
    JSTypeExpression texp = td.getTypeExpr();
    JSType tdType;
    if (texp == null) {
      warnings.add(
          JSError.make(td.getTypeExprForErrorReporting().getRoot(), CIRCULAR_TYPEDEF_ENUM));
      tdType = JSType.UNKNOWN;
    } else {
      tdType = getTypeFromJSTypeExpression(texp, registry, null);
    }
    td.resolveTypedef(tdType);
  }

  private JSType getEnumPropType(EnumType e, DeclaredTypeRegistry registry) {
    resolveEnum(e, registry);
    return e.getPropType();
  }

  public void resolveEnum(EnumType e, DeclaredTypeRegistry registry) {
    Preconditions.checkState(
        e != null, "getEnum should only be " + "called when we know that the enum is defined");
    if (e.isResolved()) {
      return;
    }
    JSTypeExpression texp = e.getTypeExpr();
    JSType enumeratedType;
    if (texp == null) {
      warnings.add(JSError.make(e.getTypeExprForErrorReporting().getRoot(), CIRCULAR_TYPEDEF_ENUM));
      enumeratedType = JSType.UNKNOWN;
    } else {
      int numTypeVars = howmanyTypeVars;
      enumeratedType = getTypeFromJSTypeExpression(texp, registry, null);
      if (howmanyTypeVars > numTypeVars) {
        warnings.add(JSError.make(texp.getRoot(), ENUM_WITH_TYPEVARS));
        enumeratedType = JSType.UNKNOWN;
        howmanyTypeVars = numTypeVars;
      } else if (enumeratedType.isTop()) {
        warnings.add(JSError.make(texp.getRoot(), ENUM_IS_TOP));
        enumeratedType = JSType.UNKNOWN;
      } else if (enumeratedType.isUnion()) {
        warnings.add(JSError.make(texp.getRoot(), ENUM_IS_UNION));
        enumeratedType = JSType.UNKNOWN;
      }
    }
    e.resolveEnum(enumeratedType);
  }

  private JSType getNominalTypeHelper(
      RawNominalType rawType,
      Node n,
      DeclaredTypeRegistry registry,
      ImmutableList<String> outerTypeParameters)
      throws UnknownTypeException {
    NominalType uninstantiated = rawType.getAsNominalType();
    if (!rawType.isGeneric() && !n.hasChildren()) {
      return rawType.getInstanceWithNullability(NULLABLE_TYPES_BY_DEFAULT);
    }
    ImmutableList.Builder<JSType> typeList = ImmutableList.builder();
    if (n.hasChildren()) {
      // Compute instantiation of polymorphic class/interface.
      Preconditions.checkState(n.getFirstChild().isBlock(), n);
      for (Node child : n.getFirstChild().children()) {
        typeList.add(getTypeFromCommentHelper(child, registry, outerTypeParameters));
      }
    }
    ImmutableList<JSType> typeArguments = typeList.build();
    ImmutableList<String> typeParameters = rawType.getTypeParameters();
    int typeArgsSize = typeArguments.size();
    int typeParamsSize = typeParameters.size();
    if (typeArgsSize != typeParamsSize) {
      // We used to also warn when (typeArgsSize < typeParamsSize), but it
      // happens so often that we stopped. Array, Object and goog.Promise are
      // common culprits, but many other types as well.
      if (typeArgsSize > typeParamsSize) {
        warnings.add(
            JSError.make(
                n,
                INVALID_GENERICS_INSTANTIATION,
                uninstantiated.getName(),
                String.valueOf(typeParamsSize),
                String.valueOf(typeArgsSize)));
      }
      return maybeMakeNullable(
          JSType.fromObjectType(
              ObjectType.fromNominalType(
                  uninstantiated.instantiateGenerics(
                      fixLengthOfTypeList(typeParameters.size(), typeArguments)))));
    }
    return maybeMakeNullable(
        JSType.fromObjectType(
            ObjectType.fromNominalType(uninstantiated.instantiateGenerics(typeArguments))));
  }

  private static List<JSType> fixLengthOfTypeList(int desiredLength, List<JSType> typeList) {
    int length = typeList.size();
    if (length == desiredLength) {
      return typeList;
    }
    ImmutableList.Builder<JSType> builder = ImmutableList.builder();
    for (int i = 0; i < desiredLength; i++) {
      builder.add(i < length ? typeList.get(i) : JSType.UNKNOWN);
    }
    return builder.build();
  }

  // Computes a type from a jsdoc that includes a function type, rather than
  // one that includes @param, @return, etc.
  private JSType getFunTypeHelper(
      Node jsdocNode, DeclaredTypeRegistry registry, ImmutableList<String> typeParameters)
      throws UnknownTypeException {
    FunctionTypeBuilder builder = new FunctionTypeBuilder();
    fillInFunTypeBuilder(jsdocNode, null, registry, typeParameters, builder);
    return registry.getCommonTypes().fromFunctionType(builder.buildFunction());
  }

  private void fillInFunTypeBuilder(
      Node jsdocNode,
      RawNominalType ownerType,
      DeclaredTypeRegistry registry,
      ImmutableList<String> typeParameters,
      FunctionTypeBuilder builder)
      throws UnknownTypeException {
    Node child = jsdocNode.getFirstChild();
    if (child.getType() == Token.THIS) {
      if (ownerType == null) {
        builder.addReceiverType(getThisOrNewType(child.getFirstChild(), registry, typeParameters));
      }
      child = child.getNext();
    } else if (child.getType() == Token.NEW) {
      Node newTypeNode = child.getFirstChild();
      JSType t = getThisOrNewType(newTypeNode, registry, typeParameters);
      if (!t.isSubtypeOf(JSType.TOP_OBJECT) && (!t.hasTypeVariable() || t.hasScalar())) {
        warnings.add(JSError.make(newTypeNode, NEW_EXPECTS_OBJECT_OR_TYPEVAR, t.toString()));
      }
      builder.addNominalType(t);
      child = child.getNext();
    }
    if (child.getType() == Token.PARAM_LIST) {
      for (Node arg = child.getFirstChild(); arg != null; arg = arg.getNext()) {
        try {
          switch (arg.getType()) {
            case Token.EQUALS:
              builder.addOptFormal(
                  getTypeFromCommentHelper(arg.getFirstChild(), registry, typeParameters));
              break;
            case Token.ELLIPSIS:
              Node restNode = arg.getFirstChild();
              builder.addRestFormals(
                  restNode == null
                      ? JSType.UNKNOWN
                      : getTypeFromCommentHelper(restNode, registry, typeParameters));
              break;
            default:
              builder.addReqFormal(getTypeFromCommentHelper(arg, registry, typeParameters));
              break;
          }
        } catch (FunctionTypeBuilder.WrongParameterOrderException e) {
          warnings.add(JSError.make(jsdocNode, WRONG_PARAMETER_ORDER));
          builder.addPlaceholderFormal();
        }
      }
      child = child.getNext();
    }
    builder.addRetType(getTypeFromCommentHelper(child, registry, typeParameters));
  }

  private JSType getThisOrNewType(
      Node n, DeclaredTypeRegistry registry, ImmutableList<String> typeParameters) {
    JSType t = getTypeFromComment(n, registry, typeParameters);
    return t.isSingletonObjWithNull() ? t.removeType(JSType.NULL) : t;
  }

  private ImmutableSet<NominalType> getImplementedInterfaces(
      JSDocInfo jsdoc, DeclaredTypeRegistry registry, ImmutableList<String> typeParameters) {
    return getInterfacesHelper(jsdoc, registry, typeParameters, true);
  }

  private ImmutableSet<NominalType> getExtendedInterfaces(
      JSDocInfo jsdoc, DeclaredTypeRegistry registry, ImmutableList<String> typeParameters) {
    return getInterfacesHelper(jsdoc, registry, typeParameters, false);
  }

  private ImmutableSet<NominalType> getInterfacesHelper(
      JSDocInfo jsdoc,
      DeclaredTypeRegistry registry,
      ImmutableList<String> typeParameters,
      boolean implementedIntfs) {
    ImmutableSet.Builder<NominalType> builder = ImmutableSet.builder();
    for (JSTypeExpression texp :
        (implementedIntfs ? jsdoc.getImplementedInterfaces() : jsdoc.getExtendedInterfaces())) {
      Node expRoot = texp.getRoot();
      JSType interfaceType = getMaybeTypeFromComment(expRoot, registry, typeParameters);
      if (interfaceType != null) {
        NominalType nt = interfaceType.getNominalTypeIfSingletonObj();
        if (nt != null && nt.isInterface()) {
          builder.add(nt);
        } else if (implementedIntfs) {
          warnings.add(JSError.make(expRoot, IMPLEMENTS_NON_INTERFACE, interfaceType.toString()));
        } else {
          warnings.add(JSError.make(expRoot, EXTENDS_NON_INTERFACE, interfaceType.toString()));
        }
      }
    }
    return builder.build();
  }

  public static class FunctionAndSlotType {
    public JSType slotType;
    public DeclaredFunctionType functionType;

    public FunctionAndSlotType(JSType slotType, DeclaredFunctionType functionType) {
      this.slotType = slotType;
      this.functionType = functionType;
    }
  }

  /**
   * Consumes either a "classic" function jsdoc with @param, @return, etc, or a jsdoc with @type
   * {function ...} and finds the types of the formal parameters and the return value. It returns a
   * builder because the callers of this function must separately handle @constructor, @interface,
   * etc.
   *
   * <p>constructorType is non-null iff this function is a constructor or interface declaration.
   */
  public FunctionAndSlotType getFunctionType(
      JSDocInfo jsdoc,
      String functionName,
      Node declNode,
      RawNominalType constructorType,
      RawNominalType ownerType,
      DeclaredTypeRegistry registry) {
    FunctionTypeBuilder builder = new FunctionTypeBuilder();
    if (ownerType != null) {
      builder.addReceiverType(ownerType.getInstanceAsJSType());
    }
    try {
      if (jsdoc != null && jsdoc.getType() != null) {
        JSType simpleType = getDeclaredTypeOfNode(jsdoc, ownerType, registry);
        if (simpleType.isUnknown() || simpleType.isTop()) {
          return qmarkFunctionDeclared;
        }
        FunctionType funType = simpleType.getFunType();
        if (funType != null) {
          JSType slotType = simpleType.isFunctionType() ? null : simpleType;
          DeclaredFunctionType declType = funType.toDeclaredFunctionType();
          if (ownerType != null && funType.getThisType() == null) {
            declType = declType.withReceiverType(ownerType.getInstanceAsJSType());
          }
          return new FunctionAndSlotType(slotType, declType);
        } else {
          warnings.add(JSError.make(declNode, FUNCTION_WITH_NONFUNC_JSDOC));
          jsdoc = null;
        }
      }
      DeclaredFunctionType declType =
          getFunTypeFromTypicalFunctionJsdoc(
              jsdoc, functionName, declNode, constructorType, ownerType, registry, builder);
      return new FunctionAndSlotType(null, declType);
    } catch (FunctionTypeBuilder.WrongParameterOrderException e) {
      warnings.add(JSError.make(declNode, WRONG_PARAMETER_ORDER));
      return qmarkFunctionDeclared;
    }
  }

  private static class ParamIterator {
    /** The parameter names from the JSDocInfo. Only set if 'params' is null. */
    Iterator<String> paramNames;

    /** The PARAM_LIST node containing the function parameters. Only set if 'paramNames' is null. */
    Node params;

    int index = -1;

    ParamIterator(Node params, JSDocInfo jsdoc) {
      Preconditions.checkArgument(params != null || jsdoc != null);
      if (params != null) {
        this.params = params;
        this.paramNames = null;
      } else {
        this.params = null;
        this.paramNames = jsdoc.getParameterNames().iterator();
      }
    }

    boolean hasNext() {
      if (paramNames != null) {
        return paramNames.hasNext();
      }
      return index + 1 < params.getChildCount();
    }

    String nextString() {
      if (paramNames != null) {
        return paramNames.next();
      }
      index++;
      return params.getChildAtIndex(index).getString();
    }

    Node getNode() {
      if (paramNames != null) {
        return null;
      }
      return params.getChildAtIndex(index);
    }
  }

  private DeclaredFunctionType getFunTypeFromTypicalFunctionJsdoc(
      JSDocInfo jsdoc,
      String functionName,
      Node funNode,
      RawNominalType constructorType,
      RawNominalType ownerType,
      DeclaredTypeRegistry registry,
      FunctionTypeBuilder builder) {
    ImmutableList.Builder<String> typeParamsBuilder = ImmutableList.builder();
    ImmutableList<String> typeParameters = ImmutableList.of();
    Node parent = funNode.getParent();

    // TODO(dimvar): need more @template warnings
    // - warn for multiple @template annotations
    // - warn for @template annotation w/out usage

    boolean ignoreJsdoc = false;
    if (jsdoc != null) {
      if (constructorType != null) {
        // We have created new names for these type variables in GTI, don't
        // create new ones here.
        typeParamsBuilder.addAll(constructorType.getTypeParameters());
      } else {
        for (String typeParam : jsdoc.getTemplateTypeNames()) {
          typeParamsBuilder.add(this.nameGen.getNextName(typeParam));
        }
      }
      // We don't properly support the type transformation language; we treat
      // its type variables as ordinary type variables.
      for (String typeParam : jsdoc.getTypeTransformations().keySet()) {
        typeParamsBuilder.add(this.nameGen.getNextName(typeParam));
      }
      typeParameters = typeParamsBuilder.build();
      if (!typeParameters.isEmpty()) {
        if (parent.isSetterDef() || parent.isGetterDef()) {
          ignoreJsdoc = true;
          jsdoc = null;
          warnings.add(JSError.make(funNode, TEMPLATED_GETTER_SETTER));
        } else {
          builder.addTypeParameters(typeParameters);
        }
      }
    }
    if (ownerType != null) {
      typeParamsBuilder.addAll(ownerType.getTypeParameters());
      typeParameters = typeParamsBuilder.build();
    }

    fillInFormalParameterTypes(jsdoc, funNode, typeParameters, registry, builder, ignoreJsdoc);
    fillInReturnType(jsdoc, funNode, parent, typeParameters, registry, builder, ignoreJsdoc);
    if (jsdoc == null) {
      return builder.buildDeclaration();
    }

    // Look at other annotations, eg, @constructor
    NominalType parentClass =
        getMaybeParentClass(jsdoc, functionName, funNode, typeParameters, registry);
    ImmutableSet<NominalType> implementedIntfs =
        getImplementedInterfaces(jsdoc, registry, typeParameters);
    if (constructorType == null && jsdoc.isConstructorOrInterface()) {
      // Anonymous type, don't register it.
      return builder.buildDeclaration();
    } else if (jsdoc.isConstructor()) {
      handleConstructorAnnotation(
          functionName, funNode, constructorType, parentClass, implementedIntfs, registry, builder);
    } else if (jsdoc.isInterface()) {
      handleInterfaceAnnotation(
          jsdoc,
          functionName,
          funNode,
          constructorType,
          implementedIntfs,
          typeParameters,
          registry,
          builder);
    } else if (!implementedIntfs.isEmpty()) {
      warnings.add(JSError.make(funNode, IMPLEMENTS_WITHOUT_CONSTRUCTOR, functionName));
    }

    if (jsdoc.hasThisType()) {
      Node thisRoot = jsdoc.getThisType().getRoot();
      Preconditions.checkState(thisRoot.getType() == Token.BANG);
      builder.addReceiverType(getThisOrNewType(thisRoot.getFirstChild(), registry, typeParameters));
    }

    return builder.buildDeclaration();
  }

  private void fillInFormalParameterTypes(
      JSDocInfo jsdoc,
      Node funNode,
      ImmutableList<String> typeParameters,
      DeclaredTypeRegistry registry,
      FunctionTypeBuilder builder,
      boolean ignoreJsdoc /* for when the jsdoc is malformed */) {
    boolean ignoreFunNode = !funNode.isFunction();
    Node params = ignoreFunNode ? null : funNode.getSecondChild();
    ParamIterator iterator = new ParamIterator(params, jsdoc);
    while (iterator.hasNext()) {
      String pname = iterator.nextString();
      Node param = iterator.getNode();
      ParameterKind p = ParameterKind.REQUIRED;
      if (param != null && convention.isOptionalParameter(param)) {
        p = ParameterKind.OPTIONAL;
      } else if (param != null && convention.isVarArgsParameter(param)) {
        p = ParameterKind.REST;
      }
      ParameterType inlineParamType =
          (ignoreJsdoc || ignoreFunNode || param.getJSDocInfo() == null)
              ? null
              : parseParameter(param.getJSDocInfo().getType(), p, registry, typeParameters);
      ParameterType fnParamType = inlineParamType;
      JSTypeExpression jsdocExp = jsdoc == null ? null : jsdoc.getParameterType(pname);
      if (jsdocExp != null) {
        if (inlineParamType == null) {
          fnParamType = parseParameter(jsdocExp, p, registry, typeParameters);
        } else {
          warnings.add(JSError.make(param, TWO_JSDOCS, "formal parameter " + pname));
        }
      }
      JSType t = null;
      if (fnParamType != null) {
        p = fnParamType.kind;
        t = fnParamType.type;
      }
      switch (p) {
        case REQUIRED:
          builder.addReqFormal(t);
          break;
        case OPTIONAL:
          builder.addOptFormal(t);
          break;
        case REST:
          builder.addRestFormals(t != null ? t : JSType.UNKNOWN);
          break;
      }
    }
  }

  private void fillInReturnType(
      JSDocInfo jsdoc,
      Node funNode,
      Node parent,
      ImmutableList<String> typeParameters,
      DeclaredTypeRegistry registry,
      FunctionTypeBuilder builder,
      boolean ignoreJsdoc /* for when the jsdoc is malformed */) {
    JSDocInfo inlineRetJsdoc = ignoreJsdoc ? null : funNode.getFirstChild().getJSDocInfo();
    JSTypeExpression retTypeExp = jsdoc == null ? null : jsdoc.getReturnType();
    if (parent.isSetterDef() && retTypeExp == null) {
      // inline returns for getters/setters are not parsed
      builder.addRetType(JSType.UNDEFINED);
    } else if (inlineRetJsdoc != null) {
      builder.addRetType(getDeclaredTypeOfNode(inlineRetJsdoc, registry, typeParameters));
      if (retTypeExp != null) {
        warnings.add(JSError.make(funNode, TWO_JSDOCS, "the return type"));
      }
    } else {
      builder.addRetType(getTypeFromJSTypeExpression(retTypeExp, registry, typeParameters));
    }
  }

  private NominalType getMaybeParentClass(
      JSDocInfo jsdoc,
      String functionName,
      Node funNode,
      ImmutableList<String> typeParameters,
      DeclaredTypeRegistry registry) {
    if (!jsdoc.hasBaseType()) {
      return null;
    }
    if (!jsdoc.isConstructor()) {
      warnings.add(JSError.make(funNode, EXTENDS_NOT_ON_CTOR_OR_INTERF, functionName));
      return null;
    }
    Node docNode = jsdoc.getBaseType().getRoot();
    JSType extendedType = getMaybeTypeFromComment(docNode, registry, typeParameters);
    if (extendedType == null) {
      return null;
    }
    NominalType parentClass = extendedType.getNominalTypeIfSingletonObj();
    if (parentClass != null && parentClass.isClass()) {
      return parentClass;
    }
    if (parentClass == null) {
      warnings.add(
          JSError.make(funNode, EXTENDS_NON_OBJECT, functionName, extendedType.toString()));
    } else {
      Preconditions.checkState(parentClass.isInterface());
      warnings.add(JSError.make(funNode, CONFLICTING_EXTENDED_TYPE, "constructor", functionName));
    }
    return null;
  }

  private void handleConstructorAnnotation(
      String functionName,
      Node funNode,
      RawNominalType constructorType,
      NominalType parentClass,
      ImmutableSet<NominalType> implementedIntfs,
      DeclaredTypeRegistry registry,
      FunctionTypeBuilder builder) {
    String className = constructorType.toString();
    NominalType builtinObject = registry.getCommonTypes().getObjectType();
    if (parentClass == null && !functionName.equals("Object")) {
      parentClass = builtinObject;
    }
    if (parentClass != null) {
      if (!constructorType.addSuperClass(parentClass)) {
        warnings.add(JSError.make(funNode, INHERITANCE_CYCLE, className));
      } else if (parentClass != builtinObject) {
        if (constructorType.isStruct() && !parentClass.isStruct()) {
          warnings.add(JSError.make(funNode, CONFLICTING_SHAPE_TYPE, "struct", className));
        } else if (constructorType.isDict() && !parentClass.isDict()) {
          warnings.add(JSError.make(funNode, CONFLICTING_SHAPE_TYPE, "dict", className));
        }
      }
    }
    if (constructorType.isDict() && !implementedIntfs.isEmpty()) {
      warnings.add(JSError.make(funNode, DICT_IMPLEMENTS_INTERF, className));
    }
    boolean noCycles = constructorType.addInterfaces(implementedIntfs);
    Preconditions.checkState(noCycles);
    builder.addNominalType(constructorType.getInstanceAsJSType());
  }

  private void handleInterfaceAnnotation(
      JSDocInfo jsdoc,
      String functionName,
      Node funNode,
      RawNominalType constructorType,
      ImmutableSet<NominalType> implementedIntfs,
      ImmutableList<String> typeParameters,
      DeclaredTypeRegistry registry,
      FunctionTypeBuilder builder) {
    if (!implementedIntfs.isEmpty()) {
      warnings.add(JSError.make(funNode, CONFLICTING_IMPLEMENTED_TYPE, functionName));
    }
    ImmutableSet<NominalType> extendedInterfaces =
        getExtendedInterfaces(jsdoc, registry, typeParameters);
    boolean noCycles =
        constructorType.addInterfaces(
            extendedInterfaces.isEmpty()
                ? ImmutableSet.of(registry.getCommonTypes().getObjectType())
                : extendedInterfaces);
    if (!noCycles) {
      warnings.add(JSError.make(funNode, INHERITANCE_CYCLE, constructorType.toString()));
    }
    builder.addNominalType(constructorType.getInstanceAsJSType());
  }

  // /** @param {...?} var_args */ function f(var_args) { ... }
  // var_args shouldn't be used in the body of f
  public static boolean isRestArg(JSDocInfo funJsdoc, String formalParamName) {
    if (funJsdoc == null) {
      return false;
    }
    JSTypeExpression texp = funJsdoc.getParameterType(formalParamName);
    Node jsdocNode = texp == null ? null : texp.getRoot();
    return jsdocNode != null && jsdocNode.getType() == Token.ELLIPSIS;
  }

  private ParameterType parseParameter(
      JSTypeExpression jsdoc,
      ParameterKind p,
      DeclaredTypeRegistry registry,
      ImmutableList<String> typeParameters) {
    if (jsdoc == null) {
      return null;
    }
    return parseParameter(jsdoc.getRoot(), p, registry, typeParameters);
  }

  private ParameterType parseParameter(
      Node jsdoc,
      ParameterKind p,
      DeclaredTypeRegistry registry,
      ImmutableList<String> typeParameters) {
    if (jsdoc == null) {
      return null;
    }
    switch (jsdoc.getType()) {
      case Token.EQUALS:
        p = ParameterKind.OPTIONAL;
        jsdoc = jsdoc.getFirstChild();
        break;
      case Token.ELLIPSIS:
        p = ParameterKind.REST;
        jsdoc = jsdoc.getFirstChild();
        break;
    }
    JSType t = getMaybeTypeFromComment(jsdoc, registry, typeParameters);
    return new ParameterType(t, p);
  }

  private static class ParameterType {
    private JSType type;
    private ParameterKind kind;

    ParameterType(JSType type, ParameterKind kind) {
      this.type = type;
      this.kind = kind;
    }
  }

  private static enum ParameterKind {
    REQUIRED,
    OPTIONAL,
    REST,
  }
}
/**
 * Checks when a function is annotated as returning {SomeType} (nullable) but actually always
 * returns {!SomeType}, i.e. never returns null.
 */
public final class CheckNullableReturn implements HotSwapCompilerPass, NodeTraversal.Callback {
  final AbstractCompiler compiler;

  public static final DiagnosticType NULLABLE_RETURN =
      DiagnosticType.warning(
          "JSC_NULLABLE_RETURN",
          "This function''s return type is nullable, but it always returns a "
              + "non-null value. Consider making the return type non-nullable.");

  public static final DiagnosticType NULLABLE_RETURN_WITH_NAME =
      DiagnosticType.warning(
          "JSC_NULLABLE_RETURN_WITH_NAME",
          "The return type of the function \"{0}\" is nullable, but it always "
              + "returns a non-null value. Consider making the return type "
              + "non-nullable.");

  private static final Predicate<Node> NULLABLE_RETURN_PREDICATE =
      new Predicate<Node>() {
        @Override
        public boolean apply(Node input) {
          // Check for null because the control flow graph's implicit return node is
          // represented by null, so this value might be input.
          if (input == null || !input.isReturn()) {
            return false;
          }
          Node returnValue = input.getFirstChild();
          return returnValue != null && isNullable(returnValue);
        }
      };

  public CheckNullableReturn(AbstractCompiler compiler) {
    this.compiler = compiler;
  }

  public static boolean hasReturnDeclaredNullable(Node n) {
    return n.isBlock()
        && n.hasChildren()
        && isReturnTypeNullable(n.getParent())
        && !hasSingleThrow(n);
  }

  @Override
  public void visit(NodeTraversal t, Node n, Node parent) {
    // Do the checks when 'n' is the block node and 'parent' is the function
    // node, so that getControlFlowGraph will return the graph inside
    // the function, rather than the graph of the enclosing scope.
    if (hasReturnDeclaredNullable(n) && !canReturnNull(t.getControlFlowGraph())) {
      String fnName = NodeUtil.getNearestFunctionName(parent);
      if (fnName != null && !fnName.isEmpty()) {
        compiler.report(t.makeError(parent, NULLABLE_RETURN_WITH_NAME, fnName));
      } else {
        compiler.report(t.makeError(parent, NULLABLE_RETURN));
      }
    }
  }

  /** @return whether the blockNode contains only a single "throw" child node. */
  private static boolean hasSingleThrow(Node blockNode) {
    if (blockNode.getChildCount() == 1 && blockNode.getFirstChild().getType() == Token.THROW) {
      // Functions consisting of a single "throw FOO" can be actually abstract,
      // so do not check their return type nullability.
      return true;
    }

    return false;
  }

  /**
   * @return True if n is a function node which is explicitly annotated as returning a nullable
   *     type, other than {?}.
   */
  private static boolean isReturnTypeNullable(Node n) {
    if (n == null || !n.isFunction()) {
      return false;
    }
    FunctionType functionType = n.getJSType().toMaybeFunctionType();
    if (functionType == null) {
      // If the JSDoc declares a non-function type on a function node, we still shouldn't crash.
      return false;
    }
    JSType returnType = functionType.getReturnType();
    if (returnType == null || returnType.isUnknownType() || !returnType.isNullable()) {
      return false;
    }
    JSDocInfo info = NodeUtil.getBestJSDocInfo(n);
    return info != null && info.hasReturnType();
  }

  /** @return True if the given ControlFlowGraph could return null. */
  public static boolean canReturnNull(ControlFlowGraph<Node> graph) {
    CheckPathsBetweenNodes<Node, ControlFlowGraph.Branch> test =
        new CheckPathsBetweenNodes<>(
            graph,
            graph.getEntry(),
            graph.getImplicitReturn(),
            NULLABLE_RETURN_PREDICATE,
            Predicates.<DiGraphEdge<Node, ControlFlowGraph.Branch>>alwaysTrue());

    return test.somePathsSatisfyPredicate();
  }

  /**
   * @return True if the node represents a nullable value. Essentially, this is just
   *     n.getJSType().isNullable(), but for purposes of this pass, the expression {@code x || null}
   *     is considered nullable even if x is always truthy. This often happens with expressions like
   *     {@code arr[i] || null}: The compiler doesn't know that arr[i] can be undefined.
   */
  private static boolean isNullable(Node n) {
    return n.getJSType().isNullable() || (n.isOr() && n.getLastChild().isNull());
  }

  @Override
  public boolean shouldTraverse(NodeTraversal nodeTraversal, Node n, Node parent) {
    return true;
  }

  @Override
  public void process(Node externs, Node root) {
    NodeTraversal.traverseEs6(compiler, root, this);
  }

  @Override
  public void hotSwapScript(Node scriptRoot, Node originalRoot) {
    NodeTraversal.traverseEs6(compiler, originalRoot, this);
  }
}