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LibJS: Correctly parse yield-from expressions

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This commit implements parsing for `yield *expr`, and the multiple
ways something can or can't be parsed like that.
Also makes yield-from a TODO in the bytecode generator.
Behold, the glory of javascript syntax:
```js
// 'yield' = expression in generators.
function* foo() {
    yield
    *bar; // <- Syntax error here, expression can't start with *
}

// 'yield' = identifier anywhere else.
function foo() {
    yield
    *bar; // Perfectly fine, this is just `yield * bar`
}
```
This commit is contained in:
Ali Mohammad Pur 2021-06-14 15:46:41 +04:30 committed by Linus Groh
parent d374295a26
commit 3194177dce
Notes: sideshowbarker 2024-07-18 12:15:02 +09:00 
Author: https://github.com/alimpfard
Commit: https://github.com/SerenityOS/serenity/commit/3194177dce7
Pull-request: https://github.com/SerenityOS/serenity/pull/8050
Reviewed-by: https://github.com/linusg
5 changed files with 67 additions and 42 deletions
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5
Userland/Libraries/LibJS/AST.h
View file

@ -348,13 +348,15 @@ public:
class YieldExpression final : public Expression {
public:
explicit YieldExpression(SourceRange source_range, RefPtr<Expression> argument)
explicit YieldExpression(SourceRange source_range, RefPtr<Expression> argument, bool is_yield_from)
: Expression(move(source_range))
, m_argument(move(argument))
, m_is_yield_from(is_yield_from)
{
}
Expression const* argument() const { return m_argument; }
bool is_yield_from() const { return m_is_yield_from; }
virtual Value execute(Interpreter&, GlobalObject&) const override;
virtual void dump(int indent) const override;
@ -362,6 +364,7 @@ public:
private:
RefPtr<Expression> m_argument;
bool m_is_yield_from { false };
};
class ReturnStatement final : public Statement {

3
Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
View file

@ -721,6 +721,9 @@ void YieldExpression::generate_bytecode(Bytecode::Generator& generator) const
{
VERIFY(generator.is_in_generator_function());
if (m_is_yield_from)
TODO();
if (m_argument)
m_argument->generate_bytecode(generator);

92
Userland/Libraries/LibJS/Parser.cpp
View file

@ -496,7 +496,9 @@ NonnullRefPtr<ClassExpression> Parser::parse_class_expression(bool expect_class_
if (match(TokenType::Extends)) {
consume();
super_class = parse_primary_expression();
auto [expression, should_continue_parsing] = parse_primary_expression();
super_class = move(expression);
(void)should_continue_parsing;
}
consume(TokenType::CurlyOpen);
@ -612,11 +614,11 @@ NonnullRefPtr<ClassExpression> Parser::parse_class_expression(bool expect_class_
return create_ast_node<ClassExpression>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }, move(class_name), move(constructor), move(super_class), move(methods));
}
NonnullRefPtr<Expression> Parser::parse_primary_expression()
Parser::PrimaryExpressionParseResult Parser::parse_primary_expression()
{
auto rule_start = push_start();
if (match_unary_prefixed_expression())
return parse_unary_prefixed_expression();
return { parse_unary_prefixed_expression() };
switch (m_parser_state.m_current_token.type()) {
case TokenType::ParenOpen: {
@ -625,7 +627,7 @@ NonnullRefPtr<Expression> Parser::parse_primary_expression()
if ((match(TokenType::ParenClose) || match(TokenType::Identifier) || match(TokenType::TripleDot)) && !try_parse_arrow_function_expression_failed_at_position(paren_position)) {
auto arrow_function_result = try_parse_arrow_function_expression(true);
if (!arrow_function_result.is_null())
return arrow_function_result.release_nonnull();
return { arrow_function_result.release_nonnull() };
set_try_parse_arrow_function_expression_failed_at_position(paren_position, true);
}
@ -634,24 +636,24 @@ NonnullRefPtr<Expression> Parser::parse_primary_expression()
if (is<FunctionExpression>(*expression)) {
static_cast<FunctionExpression&>(*expression).set_cannot_auto_rename();
}
return expression;
return { move(expression) };
}
case TokenType::This:
consume();
return create_ast_node<ThisExpression>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() });
return { create_ast_node<ThisExpression>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }) };
case TokenType::Class:
return parse_class_expression(false);
return { parse_class_expression(false) };
case TokenType::Super:
consume();
if (!m_parser_state.m_allow_super_property_lookup)
syntax_error("'super' keyword unexpected here");
return create_ast_node<SuperExpression>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() });
return { create_ast_node<SuperExpression>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }) };
case TokenType::Identifier: {
read_as_identifier:;
if (!try_parse_arrow_function_expression_failed_at_position(position())) {
auto arrow_function_result = try_parse_arrow_function_expression(false);
if (!arrow_function_result.is_null())
return arrow_function_result.release_nonnull();
return { arrow_function_result.release_nonnull() };
set_try_parse_arrow_function_expression_failed_at_position(position(), true);
}
@ -671,47 +673,47 @@ NonnullRefPtr<Expression> Parser::parse_primary_expression()
++i;
}
}
return create_ast_node<Identifier>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }, string, argument_index);
return { create_ast_node<Identifier>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }, string, argument_index) };
}
case TokenType::NumericLiteral:
return create_ast_node<NumericLiteral>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }, consume_and_validate_numeric_literal().double_value());
return { create_ast_node<NumericLiteral>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }, consume_and_validate_numeric_literal().double_value()) };
case TokenType::BigIntLiteral:
return create_ast_node<BigIntLiteral>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }, consume().value());
return { create_ast_node<BigIntLiteral>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }, consume().value()) };
case TokenType::BoolLiteral:
return create_ast_node<BooleanLiteral>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }, consume().bool_value());
return { create_ast_node<BooleanLiteral>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }, consume().bool_value()) };
case TokenType::StringLiteral:
return parse_string_literal(consume());
return { parse_string_literal(consume()) };
case TokenType::NullLiteral:
consume();
return create_ast_node<NullLiteral>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() });
return { create_ast_node<NullLiteral>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }) };
case TokenType::CurlyOpen:
return parse_object_expression();
return { parse_object_expression() };
case TokenType::Function:
return parse_function_node<FunctionExpression>();
return { parse_function_node<FunctionExpression>() };
case TokenType::BracketOpen:
return parse_array_expression();
return { parse_array_expression() };
case TokenType::RegexLiteral:
return parse_regexp_literal();
return { parse_regexp_literal() };
case TokenType::TemplateLiteralStart:
return parse_template_literal(false);
return { parse_template_literal(false) };
case TokenType::New: {
auto new_start = position();
auto new_target_result = try_parse_new_target_expression();
if (!new_target_result.is_null()) {
if (!m_parser_state.m_in_function_context)
syntax_error("'new.target' not allowed outside of a function", new_start);
return new_target_result.release_nonnull();
return { new_target_result.release_nonnull() };
}
return parse_new_expression();
return { parse_new_expression() };
}
case TokenType::Yield:
if (!m_parser_state.m_in_generator_function_context)
goto read_as_identifier;
return parse_yield_expression();
return { parse_yield_expression(), false };
default:
expected("primary expression");
consume();
return create_ast_node<ErrorExpression>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() });
return { create_ast_node<ErrorExpression>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }) };
}
}
@ -1024,23 +1026,25 @@ NonnullRefPtr<TemplateLiteral> Parser::parse_template_literal(bool is_tagged)
NonnullRefPtr<Expression> Parser::parse_expression(int min_precedence, Associativity associativity, const Vector<TokenType>& forbidden)
{
auto rule_start = push_start();
auto expression = parse_primary_expression();
auto [expression, should_continue_parsing] = parse_primary_expression();
while (match(TokenType::TemplateLiteralStart)) {
auto template_literal = parse_template_literal(true);
expression = create_ast_node<TaggedTemplateLiteral>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }, move(expression), move(template_literal));
}
while (match_secondary_expression(forbidden)) {
int new_precedence = g_operator_precedence.get(m_parser_state.m_current_token.type());
if (new_precedence < min_precedence)
break;
if (new_precedence == min_precedence && associativity == Associativity::Left)
break;
if (should_continue_parsing) {
while (match_secondary_expression(forbidden)) {
int new_precedence = g_operator_precedence.get(m_parser_state.m_current_token.type());
if (new_precedence < min_precedence)
break;
if (new_precedence == min_precedence && associativity == Associativity::Left)
break;
Associativity new_associativity = operator_associativity(m_parser_state.m_current_token.type());
expression = parse_secondary_expression(move(expression), new_precedence, new_associativity);
while (match(TokenType::TemplateLiteralStart)) {
auto template_literal = parse_template_literal(true);
expression = create_ast_node<TaggedTemplateLiteral>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }, move(expression), move(template_literal));
Associativity new_associativity = operator_associativity(m_parser_state.m_current_token.type());
expression = parse_secondary_expression(move(expression), new_precedence, new_associativity);
while (match(TokenType::TemplateLiteralStart)) {
auto template_literal = parse_template_literal(true);
expression = create_ast_node<TaggedTemplateLiteral>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }, move(expression), move(template_literal));
}
}
}
if (match(TokenType::Comma) && min_precedence <= 1) {
@ -1303,9 +1307,19 @@ NonnullRefPtr<YieldExpression> Parser::parse_yield_expression()
auto rule_start = push_start();
consume(TokenType::Yield);
RefPtr<Expression> argument;
if (match_expression())
argument = parse_expression(0);
return create_ast_node<YieldExpression>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }, move(argument));
bool yield_from = false;
if (!m_parser_state.m_current_token.trivia_contains_line_terminator()) {
if (match(TokenType::Asterisk)) {
consume();
yield_from = true;
}
if (yield_from || match_expression())
argument = parse_expression(0);
}
return create_ast_node<YieldExpression>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }, move(argument), yield_from);
}
NonnullRefPtr<ReturnStatement> Parser::parse_return_statement()

7
Userland/Libraries/LibJS/Parser.h
View file

@ -44,6 +44,11 @@ public:
Vector<FunctionNode::Parameter> parse_formal_parameters(int& function_length, u8 parse_options = 0);
RefPtr<BindingPattern> parse_binding_pattern();
struct PrimaryExpressionParseResult {
NonnullRefPtr<Expression> result;
bool should_continue_parsing_as_expression { true };
};
NonnullRefPtr<Declaration> parse_declaration();
NonnullRefPtr<Statement> parse_statement();
NonnullRefPtr<BlockStatement> parse_block_statement();
@ -66,7 +71,7 @@ public:
NonnullRefPtr<DebuggerStatement> parse_debugger_statement();
NonnullRefPtr<ConditionalExpression> parse_conditional_expression(NonnullRefPtr<Expression> test);
NonnullRefPtr<Expression> parse_expression(int min_precedence, Associativity associate = Associativity::Right, const Vector<TokenType>& forbidden = {});
NonnullRefPtr<Expression> parse_primary_expression();
PrimaryExpressionParseResult parse_primary_expression();
NonnullRefPtr<Expression> parse_unary_prefixed_expression();
NonnullRefPtr<RegExpLiteral> parse_regexp_literal();
NonnullRefPtr<ObjectExpression> parse_object_expression();

2
Userland/Libraries/LibJS/Tests/syntax/generators.js
View file

@ -12,7 +12,7 @@ describe("parsing freestanding generators", () => {
expect(`function foo() { yield; }`).toEval();
expect(`function foo() { yield 3; }`).not.toEval();
});
test.skip("yield-from expression", () => {
test("yield-from expression", () => {
expect(`function* foo() { yield *bar; }`).toEval();
expect(`function* foo() { yield *(yield); }`).toEval();
expect(`function* foo() { yield