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Make let a contextual keyword

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This commit is contained in:
Daniel Tschinder
2019-01-21 19:46:40 -08:00
parent 65febdd13a
commit 178f2d7949
24 changed files with 636 additions and 42 deletions
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77
packages/babel-parser/src/parser/statement.js
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@@ -3,8 +3,13 @@
import * as N from "../types";
import { types as tt, type TokenType } from "../tokenizer/types";
import ExpressionParser from "./expression";
import { isIdentifierChar } from "../util/identifier";
import {
isIdentifierChar,
isIdentifierStart,
keywordRelationalOperator,
} from "../util/identifier";
import { lineBreak, skipWhiteSpace } from "../util/whitespace";
import * as charCodes from "charcodes";
// Reused empty array added for node fields that are always empty.
@@ -71,6 +76,33 @@ export default class StatementParser extends ExpressionParser {
return this.finishNode(node, "InterpreterDirective");
}
isLet() {
if (!this.isContextual("let")) {
return false;
}
skipWhiteSpace.lastIndex = this.state.pos;
const skip = skipWhiteSpace.exec(this.state.input);
// $FlowIgnore
const next = this.state.pos + skip[0].length;
const nextCh = this.state.input.charCodeAt(next);
if (
(nextCh === charCodes.leftCurlyBrace &&
!lineBreak.test(this.state.input.slice(this.state.end, next))) ||
nextCh === charCodes.leftSquareBracket
) {
return true;
}
if (isIdentifierStart(nextCh)) {
let pos = next + 1;
while (isIdentifierChar(this.state.input.charCodeAt(pos))) {
++pos;
}
const ident = this.state.input.slice(next, pos);
if (!keywordRelationalOperator.test(ident)) return true;
}
return false;
}
// Parse a single statement.
//
// If expecting a statement and finding a slash operator, parse a
@@ -86,8 +118,14 @@ export default class StatementParser extends ExpressionParser {
}
parseStatementContent(declaration: boolean, topLevel: ?boolean): N.Statement {
const starttype = this.state.type;
let starttype = this.state.type;
const node = this.startNode();
let kind;
if (this.isLet()) {
starttype = tt._var;
kind = "let";
}
// Most types of statements are recognized by the keyword they
// start with. Many are trivial to parse, some require a bit of
@@ -129,12 +167,11 @@ export default class StatementParser extends ExpressionParser {
case tt._try:
return this.parseTryStatement(node);
case tt._let:
case tt._const:
if (!declaration) this.unexpected(); // NOTE: falls through to _var
case tt._var:
return this.parseVarStatement(node, starttype);
kind = kind || this.state.value;
if (!declaration && kind !== "var") this.unexpected();
return this.parseVarStatement(node, kind);
case tt._while:
return this.parseWhileStatement(node);
@@ -424,18 +461,19 @@ export default class StatementParser extends ExpressionParser {
return this.parseFor(node, null);
}
if (this.match(tt._var) || this.match(tt._let) || this.match(tt._const)) {
const isLet = this.isLet();
if (this.match(tt._var) || this.match(tt._const) || isLet) {
const init = this.startNode();
const varKind = this.state.type;
const kind = isLet ? "let" : this.state.value;
this.next();
this.parseVar(init, true, varKind);
this.parseVar(init, true, kind);
this.finishNode(init, "VariableDeclaration");
if (this.match(tt._in) || this.isContextual("of")) {
if (init.declarations.length === 1) {
const declaration = init.declarations[0];
const isForInInitializer =
varKind === tt._var &&
kind === "var" &&
declaration.init &&
declaration.id.type != "ObjectPattern" &&
declaration.id.type != "ArrayPattern" &&
@@ -606,7 +644,7 @@ export default class StatementParser extends ExpressionParser {
parseVarStatement(
node: N.VariableDeclaration,
kind: TokenType,
kind: "var" | "let" | "const",
): N.VariableDeclaration {
this.next();
this.parseVar(node, false, kind);
@@ -862,12 +900,11 @@ export default class StatementParser extends ExpressionParser {
parseVar(
node: N.VariableDeclaration,
isFor: boolean,
kind: TokenType,
kind: "var" | "let" | "const",
): N.VariableDeclaration {
const declarations = (node.declarations = []);
const isTypescript = this.hasPlugin("typescript");
// $FlowFixMe
node.kind = kind.keyword;
node.kind = kind;
for (;;) {
const decl = this.startNode();
this.parseVarHead(decl);
@@ -875,7 +912,7 @@ export default class StatementParser extends ExpressionParser {
decl.init = this.parseMaybeAssign(isFor);
} else {
if (
kind === tt._const &&
kind === "const" &&
!(this.match(tt._in) || this.isContextual("of"))
) {
// `const` with no initializer is allowed in TypeScript.
@@ -1638,11 +1675,7 @@ export default class StatementParser extends ExpressionParser {
}
this.parseDecorators(false);
return this.parseClass(expr, true, true);
} else if (
this.match(tt._let) ||
this.match(tt._const) ||
this.match(tt._var)
) {
} else if (this.match(tt._const) || this.match(tt._var) || this.isLet()) {
return this.raise(
this.state.start,
"Only expressions, functions or classes are allowed as the `default` export.",
@@ -1661,7 +1694,7 @@ export default class StatementParser extends ExpressionParser {
isExportDefaultSpecifier(): boolean {
if (this.match(tt.name)) {
return this.state.value !== "async";
return this.state.value !== "async" && this.state.value !== "let";
}
if (!this.match(tt._default)) {
@@ -1710,9 +1743,9 @@ export default class StatementParser extends ExpressionParser {
return (
this.state.type.keyword === "var" ||
this.state.type.keyword === "const" ||
this.state.type.keyword === "let" ||
this.state.type.keyword === "function" ||
this.state.type.keyword === "class" ||
this.isLet() ||
this.isAsyncFunction()
);
}