test262: Function conformance fixes (wave 13) - #70
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Implement Function.prototype.bind (ES2024 §20.2.3.2) for the reachable subset: return a new function that prepends the saved bound arguments to its own call arguments and applies the target. As with call/apply, the thisArg is dropped (a plain function carries no receiver in this model) and the bound function does not carry the target's own length/name/ prototype properties, which would need a full function-object model. The bound closure's arity is the target length minus the number of bound arguments (floored at 0, per SetFunctionLength) so remaining call arguments forward correctly. Raises test/built-ins/Function/prototype from 17 to 30 passing.
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Implements
Function.prototype.bind(ES2024 §20.2.3.2) for the reachable subset.What
func_bind/2returns a partially-applied function: it prepends the saved bound arguments to each call's own arguments and applies the target. Bound closure arity = target length − #bound args (floored at 0, per SetFunctionLength), so remaining call args forward correctly; extra trailing args are dropped by the same arity-fitting call/apply already use.x.bind(...)inlower.gleambesidecall/apply(func_bindop); a non-function receiver delegates to a same-named userbindmethod.Deviations (documented, gated on absent function-object model)
thisArgis dropped — plain functions carry no receiver in this model (same as call/apply).length/name/prototype; property-bearing function objects are out of scope for v1.Impact
test/built-ins/Function/prototype: pass 17 → 30 (+13), runtime_error 36 → 21. No pass regressions. New spec-driven tests appended tojs_compiler_test.gleam.Out of scope (honest): the bulk of the remaining Function/prototype failures are gated on a full function-object model (
.length/.name/prototype/caller/argumentspoisoning), real this-binding,Object.defineProperty, theargumentsobject,[[Construct]]on bound functions, and theFunctionconstructor /eval(permanent AOT boundary).