Only start a destructuring pattern at the head of an AssignmentExpression - #1652
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Only start a destructuring pattern at the head of an AssignmentExpression#1652andreasrosdal wants to merge 4 commits into
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`[a] = b` and `{a} = b` are AssignmentExpressions whose target happens to
be written like a literal. They are only reachable through
AssignmentExpression : LeftHandSideExpression = AssignmentExpression, so an
array or object literal anywhere else in an expression cannot begin one:
`0 || [a] = b` has no production, because a LogicalORExpression is not a
valid assignment target.
js_parse_postfix_expr() decides purely by peeking past the closing bracket
for a '=', without knowing where in the expression it is, so it accepts
programs with no parse:
0 || [a] = b; // -> 1
0 || {p:a} = b; // -> [object Object]
V8 rejects both with "Invalid left-hand side in assignment".
Add PF_PATTERN, set by js_parse_assign_expr2() when it starts the
ConditionalExpression that may turn out to be an assignment target, and
threaded down the unary/binary chain. Every recursive call that descends
into a non-leftmost operand clears it, so only the leftmost literal is
considered.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014mv33YvfHz7t9mmkituBnn
Covers the positions where an object/array literal must stay a literal (binary, short circuit, unary and private-name-in operands) and the head positions that must keep parsing as a pattern: statement level, both branches of a conditional, comma elements, call arguments, literal elements, initialisers, default parameter values, arrow bodies and the three for loop forms. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01K6eRbuuuCujKgQkrHgvMrc
`#field in {} = 0` must be an early SyntaxError. It was not one because the
`{}` was taken for a destructuring pattern on the strength of the `=` that
follows, which is exactly what this change stops; test262's
private-field-invalid-assignment-target now passes in both modes.
Leaving the two entries behind makes the full test262 run exit non-zero for
errors that are fixed rather than new. Also covers the construct in the
local test, next to the array form already there.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01K6eRbuuuCujKgQkrHgvMrc
The rule is positional, so the test is mostly a list of positions. Added the ones the first round did not name: a NewExpression callee and argument, an update operand, a member access or call on a literal, an optional chain, every compound assignment operator, the head of each statement that takes a full Expression, an argument, array element, property value and spread, the operand of yield and await, a class field initialiser, a default parameter value, a template substitution and the tag of a tagged template.
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[a] = band{a} = bare AssignmentExpressions whose target happens to be written like a literal. They are only reachable throughAssignmentExpression : LeftHandSideExpression = AssignmentExpression, so an array or object literal anywhere else in an expression cannot begin one —0 || [a] = bhas no parse, because a LogicalORExpression is not a valid assignment target.js_parse_postfix_expr()decides purely by peeking past the closing bracket for a=, without knowing where in the expression it is, so it accepts programs with no parse:V8 rejects both with Invalid left-hand side in assignment.
Add
PF_PATTERN, set byjs_parse_assign_expr2()when it starts the ConditionalExpression that may turn out to be an assignment target, and threaded down the unary/binary chain. Every recursive call that descends into a non-leftmost operand clears it, so only the leftmost literal is considered.Testing
No change against master in any of:
language/expressions/assignmentlanguage/destructuringlanguage/statements/for-oflanguage/expressions/arrow-functionlanguage/statements/variablelanguage/expressions/conditional🤖 Generated with Claude Code
https://claude.ai/code/session_014mv33YvfHz7t9mmkituBnn
Generated by Claude Code