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LibJS: Function declarations in if statement clauses

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https://tc39.es/ecma262/#sec-functiondeclarations-in-ifstatement-statement-clauses

B.3.4 FunctionDeclarations in IfStatement Statement Clauses

The following augments the IfStatement production in 13.6:

    IfStatement[Yield, Await, Return] :
        if ( Expression[+In, ?Yield, ?Await] ) FunctionDeclaration[?Yield, ?Await, ~Default] else Statement[?Yield, ?Await, ?Return]
        if ( Expression[+In, ?Yield, ?Await] ) Statement[?Yield, ?Await, ?Return] else FunctionDeclaration[?Yield, ?Await, ~Default]
        if ( Expression[+In, ?Yield, ?Await] ) FunctionDeclaration[?Yield, ?Await, ~Default] else FunctionDeclaration[?Yield, ?Await, ~Default]
        if ( Expression[+In, ?Yield, ?Await] ) FunctionDeclaration[?Yield, ?Await, ~Default]

This production only applies when parsing non-strict code. Code matching
this production is processed as if each matching occurrence of
FunctionDeclaration[?Yield, ?Await, ~Default] was the sole
StatementListItem of a BlockStatement occupying that position in the
source code. The semantics of such a synthetic BlockStatement includes
the web legacy compatibility semantics specified in B.3.3.
This commit is contained in:
Linus Groh 2020-10-31 13:37:09 +00:00 • committed by Andreas Kling
parent 778011dac6
commit a598a2c19d
Notes: sideshowbarker 2024-07-19 01:37:13 +09:00
2 changed files with 66 additions and 4 deletions
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29
Libraries/LibJS/Parser.cpp
View file

@ -1616,17 +1616,38 @@ NonnullRefPtr<CatchClause> Parser::parse_catch_clause()
NonnullRefPtr<IfStatement> Parser::parse_if_statement()
{
auto parse_function_declaration_as_block_statement = [&] {
// https://tc39.es/ecma262/#sec-functiondeclarations-in-ifstatement-statement-clauses
// Code matching this production is processed as if each matching occurrence of
// FunctionDeclaration[?Yield, ?Await, ~Default] was the sole StatementListItem
// of a BlockStatement occupying that position in the source code.
ScopePusher scope(*this, ScopePusher::Let);
auto block = create_ast_node<BlockStatement>();
block->append(parse_declaration());
block->add_functions(m_parser_state.m_function_scopes.last());
return block;
};
consume(TokenType::If);
consume(TokenType::ParenOpen);
auto predicate = parse_expression(0);
consume(TokenType::ParenClose);
auto consequent = parse_statement();
RefPtr<Statement> consequent;
if (!m_parser_state.m_strict_mode && match(TokenType::Function))
consequent = parse_function_declaration_as_block_statement();
else
consequent = parse_statement();
RefPtr<Statement> alternate;
if (match(TokenType::Else)) {
consume(TokenType::Else);
alternate = parse_statement();
consume();
if (!m_parser_state.m_strict_mode && match(TokenType::Function))
alternate = parse_function_declaration_as_block_statement();
else
alternate = parse_statement();
}
return create_ast_node<IfStatement>(move(predicate), move(consequent), move(alternate));
return create_ast_node<IfStatement>(move(predicate), move(*consequent), move(alternate));
}
NonnullRefPtr<Statement> Parser::parse_for_statement()

41
Libraries/LibJS/Tests/if-statement-function-declaration.js Normal file
View file

@ -0,0 +1,41 @@
describe("function declarations in if statement clauses", () => {
test("if clause", () => {
if (true) function foo() {}
if (false) function bar() {}
expect(typeof globalThis.foo).toBe("function");
expect(typeof globalThis.bar).toBe("undefined");
});
test("else clause", () => {
if (false);
else function foo() {}
if (true);
else function bar() {}
expect(typeof globalThis.foo).toBe("function");
expect(typeof globalThis.bar).toBe("undefined");
});
test("if and else clause", () => {
if (true) function foo() {}
else function bar() {}
expect(typeof globalThis.foo).toBe("function");
expect(typeof globalThis.bar).toBe("undefined");
});
test("syntax error in strict mode", () => {
expect(`
"use strict";
if (true) function foo() {}
`).not.toEval();
expect(`
"use strict";
if (false);
else function foo() {}
`).not.toEval();
expect(`
"use strict";
if (false) function foo() {}
else function bar() {}
`).not.toEval();
});
});