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fix(ast): accept every simple target in destructuring assignment patterns - #5596
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A destructuring assignment target that is not an object or array literal
must be a simple assignment target, and a parenthesized identifier or
property access is one. `ArrayLiteral::to_pattern` and
`ObjectLiteral::to_pattern` only knew bare identifiers and property
accesses, so `[(a), b] = list`, `({ a: (b) } = obj)`, `[...(x)] = list`
and `({...(o.p)} = obj)` were rejected. Any other target is now refined
through `AssignTarget::from_expression_simple`, which also rejects `eval`
and `arguments` in strict code (`[eval] = list`, `({ arguments } = obj)`
were accepted). A parenthesized pattern such as `[({a})] = list` stays an
error.
Object patterns also accept nested patterns and initializers under
computed and numeric property names (`({ [k]: [x] } = obj)`,
`({ 0: x = 1 } = list)`). An initializer is named only when its target is
an unparenthesized identifier (IsIdentifierRef), as the assignment parser
already does, so `[(x) = function () {}] = []` no longer names the
function. A parenthesized object or array literal is not a pattern in a
for-in/of head: `for (([x]) of list)` is a syntax error.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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It changes the following:
ArrayLiteral::to_pattern/ObjectLiteral::to_patternaccept any simple assignment target (viaAssignTarget::from_expression_simple), including parenthesized ones:[(a), b] = list,({ a: (b) } = obj),[...(x)] = list,({...(o.p)} = obj).evalandargumentsare rejected as destructuring targets in strict code ([eval] = list,({ a: eval } = obj),({ arguments } = obj),[...eval] = listwere accepted).({ [k]: [x] } = obj),({ 0: x = 1 } = list).to_pattern; it was already named by the assignment parser only when the target is an unparenthesized identifier (IsIdentifierRef), so[(x) = function () {}] = []no longer names the functionx.for (([x]) of list);is a SyntaxError.Spec: AssignmentTargetType and the destructuring assignment early errors. Fixes test262
staging/sm/expressions/destructuring-pattern-parenthesized.js,staging/sm/destructuring/order.jsandstaging/sm/destructuring/order-super.js. Found while embedding Boa in the Southstar browser.Tested with a new parser unit test (
destructuring_assignment_simple_targets).🤖 Generated with Claude Code