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make #889 more efficient and flexible

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This commit is contained in:
Sebastian McKenzie 2015-02-26 15:24:12 +11:00
parent 3f146b54ff
commit 751557aef1
1 changed files with 36 additions and 30 deletions
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66
src/babel/transformation/transformers/es6/parameters.rest.js
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@ -1,33 +1,40 @@
var util = require("../../../util");
var t = require("../../../types");
var isNumber = require("lodash/lang/isNumber");
var util = require("../../../util");
var t = require("../../../types");
exports.check = t.isRestElement;
var memberExpressionVisitor = {
var memberExpressionOptimisationVisitor = {
enter(node, parent, scope, state) {
if (t.isScope(node, parent) && !scope.bindingIdentifierEquals(state.name, state.outerDeclar)) {
// check if this scope has a local binding that will shadow the rest parameter
if (t.isScope(node, parent) && !scope.bindingIdentifierEquals(state.name, state.outerBinding)) {
return this.skip();
}
// skip over functions as whatever `arguments` we reference inside will refer
// to the wrong function
if (t.isFunctionDeclaration(node) || t.isFunctionExpression(node)) {
state.isOptimizable = false;
return this.stop();
state.noOptimise = true;
scope.traverse(node, memberExpressionOptimisationVisitor, state);
state.noOptimise = false;
return this.skip();
}
// is this a referenced identifier and is it referencing the rest parameter?
if (!t.isReferencedIdentifier(node, parent, { name: state.name })) return;
if (t.isMemberExpression(parent)) {
if (!state.noOptimise && t.isMemberExpression(parent) && parent.computed) {
// if we know that this member expression is referencing a number then we can safely
// optimise it
var prop = parent.property;
if (typeof prop.value === "number" ||
t.isUnaryExpression(prop) ||
t.isBinaryExpression(prop)) {
state.candidates.push({ node, parent });
if (isNumber(prop.value) || t.isUnaryExpression(prop) || t.isBinaryExpression(prop)) {
optimizeMemberExpression(node, parent, state.method.params.length);
state.hasShorthand = true;
return;
}
}
state.isOptimizable = false;
this.stop();
state.longForm = true;
}
};
@ -39,7 +46,7 @@ function optimizeMemberExpression(node, parent, offset) {
node.name = "arguments";
prop.value += offset;
prop.raw = String(prop.value);
} else {
} else { // Identifier
node.name = "arguments";
newExpr = t.binaryExpression("+", prop, t.literal(offset));
parent.property = newExpr;
@ -71,23 +78,22 @@ exports.Function = function (node, parent, scope) {
node.body.body.unshift(declar);
}
// check if rest is used only in member expressions
var restOuterDeclar = scope.getBindingIdentifier(rest.name);
var state = {
name: rest.name,
outerDeclar: restOuterDeclar,
isOptimizable: true,
candidates: []
};
scope.traverse(node, memberExpressionVisitor, state);
// check if rest is used in member expressions and optimise for those cases
if (state.isOptimizable) {
for (let i = 0, count = state.candidates.length; i < count; ++i) {
let candidate = state.candidates[i];
optimizeMemberExpression(candidate.node, candidate.parent, node.params.length, state.strictMode);
}
return;
}
var state = {
outerBinding: scope.getBindingIdentifier(rest.name),
hasShorthand: true,
longForm: false,
method: node,
name: rest.name,
};
scope.traverse(node, memberExpressionOptimisationVisitor, state);
// we only have shorthands and there's no other references
if (!state.longForm && state.hasShorthand) return;
//
var start = t.literal(node.params.length);
var key = scope.generateUidIdentifier("key");