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fix: the LHS in for-of loop should not start with let (#13049)

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* fix: the LHS in for-of loop should not start with let

* Update packages/babel-parser/src/parser/statement.js

Co-authored-by: Nicolò Ribaudo <nicolo.ribaudo@gmail.com>

Co-authored-by: Nicolò Ribaudo <nicolo.ribaudo@gmail.com>
This commit is contained in:
Huáng Jùnliàng
2021-03-29 16:54:23 -04:00
committed by GitHub
parent 5c0d2f6032
commit 8efbac4a5d
4 changed files with 155 additions and 5 deletions
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1
packages/babel-parser/src/parser/error-message.js
View File

@@ -57,6 +57,7 @@ export const ErrorMessages = Object.freeze({
"'from' is not allowed as an identifier after 'export default'",
ForInOfLoopInitializer:
"%0 loop variable declaration may not have an initializer",
ForOfLet: "The left-hand side of a for-of loop may not start with 'let'.",
GeneratorInSingleStatementContext:
"Generators can only be declared at the top level or inside a block",
IllegalBreakContinue: "Unsyntactic %0",

26
packages/babel-parser/src/parser/statement.js
View File

@@ -125,6 +125,19 @@ export default class StatementParser extends ExpressionParser {
if (!this.isContextual("let")) {
return false;
}
return this.isLetKeyword(context);
}
/**
* Assuming we have seen a contextual `let`, check if it starts a variable declaration
so that `left` should be interpreted as a `let` keyword.
*
* @param {?string} context When `context` is non nullish, it will return early and _skip_ checking
if the next token after `let` is `{` or a keyword relational operator
* @returns {boolean}
* @memberof StatementParser
*/
isLetKeyword(context: ?string): boolean {
const next = this.nextTokenStart();
const nextCh = this.input.charCodeAt(next);
// For ambiguous cases, determine if a LexicalDeclaration (or only a
@@ -511,7 +524,8 @@ export default class StatementParser extends ExpressionParser {
return this.parseFor(node, null);
}
const isLet = this.isLet();
const startsWithLet = this.isContextual("let");
const isLet = startsWithLet && this.isLetKeyword();
if (this.match(tt._var) || this.match(tt._const) || isLet) {
const init = this.startNode();
const kind = isLet ? "let" : this.state.value;
@@ -533,11 +547,13 @@ export default class StatementParser extends ExpressionParser {
const refExpressionErrors = new ExpressionErrors();
const init = this.parseExpression(true, refExpressionErrors);
if (this.match(tt._in) || this.isContextual("of")) {
const isForOf = this.isContextual("of");
if (isForOf || this.match(tt._in)) {
if (isForOf && startsWithLet) {
this.raise(init.start, Errors.ForOfLet);
}
this.toAssignable(init, /* isLHS */ true);
const description = this.isContextual("of")
? "for-of statement"
: "for-in statement";
const description = isForOf ? "for-of statement" : "for-in statement";
this.checkLVal(init, description);
return this.parseForIn(node, init, awaitAt);
} else {