agra 08f263c6e4 fix(ir): open a fresh defer window when lowering a lambda body (issue 0073) ...

A closure literal declared inside a `defer` body segfaulted the compiler.
Root cause: lowerLambda never opened its own `func_defer_base` window. Every
other function-lowering entry (lowerFunction / monomorphizeFunction /
monomorphizePackFn) saves func_defer_base, sets it to defer_stack.items.len, and
restores it — lowerLambda didn't. So a lambda's `return` drained the ENCLOSING
function's defers; when the defer body itself declared the lambda, draining
re-lowered the lambda, which returned, which drained again → infinite recursion
→ stack-overflow SIGSEGV (the failable variant surfaced one frame out, in
expandCallDefaults→lookupFn reading a clobbered scope).

Fix: lowerLambda now saves func_defer_base + the defer_stack length, sets the
base to the current length (a fresh window), and restores both on exit — so a
lambda's `return` drains only its own defers.

Regression: examples/0310-closures-closure-literal-in-defer.sx — a closure
declared and called inside a `defer`; verifies `body` then `defer closure: 42`
at scope exit (exit 0). Issue 0073 marked RESOLVED; repro promoted from
issues/0073-*.sx.

zig build, zig build test, tests/run_examples.sh (358/0) all green.

2026-06-02 23:29:49 +03:00

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