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Closure Compiler is a JavaScript optimizing compiler. It parses your
JavaScript, analyzes it, removes dead code and rewrites and minimizes
what's left. It also checks syntax, variable references, and types, and
warns about common JavaScript pitfalls. It is used in many of Google's
JavaScript apps, including Gmail, Google Web Search, Google Maps, and
Google Docs.
/*
* Copyright 2016 The Closure Compiler Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.javascript.jscomp;
import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.jscomp.NodeTraversal.Callback;
import com.google.javascript.rhino.Node;
/**
* Report an error if the user forgot to call super() in the constructor of an ES6 class.
* We don't require that the super() call be the first statement in the constructor, because doing
* so would break J2CL-compiled code.
*/
final class CheckMissingSuper extends AbstractPostOrderCallback implements HotSwapCompilerPass {
static final DiagnosticType MISSING_CALL_TO_SUPER =
DiagnosticType.error("JSC_MISSING_CALL_TO_SUPER", "constructor is missing a call to super()");
static final DiagnosticType THIS_BEFORE_SUPER =
DiagnosticType.error("JSC_THIS_BEFORE_SUPER", "cannot access this before calling super()");
private final AbstractCompiler compiler;
public CheckMissingSuper(AbstractCompiler compiler) {
this.compiler = compiler;
}
@Override
public void process(Node externs, Node root) {
TranspilationPasses.processCheck(compiler, root, this);
}
@Override
public void hotSwapScript(Node scriptRoot, Node originalRoot) {
TranspilationPasses.hotSwapCheck(compiler, scriptRoot, this);
}
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
if (n.isClass()) {
Node superclass = n.getSecondChild();
if (superclass.isEmpty()) {
return;
}
Node constructor =
NodeUtil.getFirstPropMatchingKey(NodeUtil.getClassMembers(n), "constructor");
if (constructor == null) {
return;
}
FindSuper finder = new FindSuper();
NodeTraversal.traverseEs6(compiler, NodeUtil.getFunctionBody(constructor), finder);
if (!finder.found) {
t.report(constructor, MISSING_CALL_TO_SUPER);
}
}
}
private static final class FindSuper implements Callback {
boolean found = false;
@Override
public boolean shouldTraverse(NodeTraversal nodeTraversal, Node n, Node parent) {
return !found;
}
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
if (n.isThis()) {
t.report(n, THIS_BEFORE_SUPER);
}
if (n.isSuper() && parent.isCall()) {
found = true;
return;
}
}
}
}