perry-codegen Phase 2: String.matchAll codegen not implemented #317

What happened

Perry's codegen aborts with a hard "not yet supported" message on any use of String.prototype.matchAll(regex):

perry-codegen Phase 2: expression StringMatchAll not yet supported

Surfaced compiling effect/src/internal/cause.ts (func 140) during the #309 compat sweep.

What you expected

MDN spec for String.prototype.matchAll: returns an iterator of all matches of a (global) regex against a string. Standard ES2020 surface, widely used.

Minimal reproduction

const text = "key=val&foo=bar&baz=qux";
const re = /([a-z]+)=([a-z]+)/g;
for (const m of text.matchAll(re)) {
  console.log(m[1], "->", m[2]);
}

perry compile repro.ts -o /tmp/out
# fails with: perry-codegen Phase 2: expression StringMatchAll not yet supported

Likely fix site

The HIR variant Expr::StringMatchAll already exists (the error message comes from a missing codegen arm), so HIR lowering is done. Adding the codegen arm in crates/perry-codegen/src/expr.rs and a runtime helper in crates/perry-runtime/src/string.rs (or a regex-aware path) should be a contained change. Consider matching the iterator-protocol shape String.prototype.match with the global flag already produces (returns array, not iterator) — matchAll is the iterator version.

Environment

• Perry version: 0.5.405
• Host OS: macOS 26.4 (arm64)
• Target: native
• Effect version: 3.21.2 (where this surfaced)

Discovered as part of the #309 long tail.