com.google.javascript.jscomp

Class CheckMissingReturn

java.lang.Object

com.google.javascript.jscomp.CheckMissingReturn

All Implemented Interfaces:

NodeTraversal.Callback, NodeTraversal.ScopedCallback

class CheckMissingReturn
extends java.lang.Object
implements NodeTraversal.ScopedCallback

Checks functions for missing return statements. Return statements are only expected for functions with return type information. Functions with empty bodies are ignored. NOTE(dimvar): Do not convert this pass to use TypeI. The pass is only used with the old type checker. The new type inference checks missing returns on its own.

Field Summary

Fields

Modifier and Type	Field and Description
private AbstractCompiler	compiler
private CodingConvention	convention
private static com.google.common.base.Predicate<DiGraph.DiGraphEdge<Node,ControlFlowGraph.Branch>>	GOES_THROUGH_TRUE_CONDITION_PREDICATE
private static com.google.common.base.Predicate<Node>	IS_RETURN
(package private) static DiagnosticType	MISSING_RETURN_STATEMENT

Constructor Summary

Constructors

Constructor and Description
CheckMissingReturn(AbstractCompiler compiler)

Method Summary

Modifier and Type	Method and Description
void	enterScope(NodeTraversal t) Called immediately after entering a new scope.
void	exitScope(NodeTraversal t) Called immediately before exiting a scope.
private JSType	explicitReturnExpected(Node scope) Determines if the given scope should explicitly return.
private boolean	fastAllPathsReturnCheck(ControlFlowGraph<Node> cfg) Fast check to see if all execution paths contain a return statement.
private static boolean	isEmptyFunction(Node function)
private boolean	isVoidOrUnknown(JSType returnType)
boolean	shouldTraverse(NodeTraversal nodeTraversal, Node n, Node parent) Visits a node in pre order (before visiting its children) and decides whether this node's children should be traversed.
void	visit(NodeTraversal t, Node n, Node parent) Visits a node in postorder (after its children have been visited).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

MISSING_RETURN_STATEMENT

static final DiagnosticType MISSING_RETURN_STATEMENT

compiler

private final AbstractCompiler compiler

convention

private final CodingConvention convention

IS_RETURN

private static final com.google.common.base.Predicate<Node> IS_RETURN

GOES_THROUGH_TRUE_CONDITION_PREDICATE

private static final com.google.common.base.Predicate<DiGraph.DiGraphEdge<Node,ControlFlowGraph.Branch>> GOES_THROUGH_TRUE_CONDITION_PREDICATE

Constructor Detail

CheckMissingReturn

CheckMissingReturn(AbstractCompiler compiler)

Method Detail

enterScope

public void enterScope(NodeTraversal t)

Description copied from interface: NodeTraversal.ScopedCallback

Called immediately after entering a new scope. The new scope can be accessed through t.getScope()

Specified by:

enterScope in interface NodeTraversal.ScopedCallback

fastAllPathsReturnCheck

private boolean fastAllPathsReturnCheck(ControlFlowGraph<Node> cfg)

Fast check to see if all execution paths contain a return statement. May spuriously report that a return statement is missing.

Returns:

true if all paths return, converse not necessarily true

exitScope

public void exitScope(NodeTraversal t)

Description copied from interface: NodeTraversal.ScopedCallback

Called immediately before exiting a scope. The ending scope can be accessed through t.getScope()

Specified by:

exitScope in interface NodeTraversal.ScopedCallback

shouldTraverse

public boolean shouldTraverse(NodeTraversal nodeTraversal,
                              Node n,
                              Node parent)

Description copied from interface: NodeTraversal.Callback

Visits a node in pre order (before visiting its children) and decides whether this node's children should be traversed. If children are traversed, they will be visited by NodeTraversal.Callback.visit(NodeTraversal, Node, Node) in postorder.

Implementations can have side effects (e.g. modifying the parse tree).

Specified by:

shouldTraverse in interface NodeTraversal.Callback

Returns:

whether the children of this node should be visited

visit

public void visit(NodeTraversal t,
                  Node n,
                  Node parent)

Description copied from interface: NodeTraversal.Callback

Visits a node in postorder (after its children have been visited). A node is visited only if all its parents should be traversed (NodeTraversal.Callback.shouldTraverse(NodeTraversal, Node, Node)).

Implementations can have side effects (e.g. modifying the parse tree).

Specified by:

visit in interface NodeTraversal.Callback

explicitReturnExpected

private JSType explicitReturnExpected(Node scope)

Determines if the given scope should explicitly return. All functions with non-void or non-unknown return types must have explicit returns. Exception: Constructors which specifically specify a return type are used to allow invocation without requiring the "new" keyword. They have an implicit return type. See unit tests.

Returns:

If a return type is expected, returns it. Otherwise, returns null.

isEmptyFunction

private static boolean isEmptyFunction(Node function)

Returns:

true if function represents a JavaScript function with an empty body

isVoidOrUnknown

private boolean isVoidOrUnknown(JSType returnType)

Returns:

true if returnType is void, unknown, or a union containing void or unknown