A module with a top-level statement, imported as source, fails with "Global is referenced by parentless instruction" #447

A module that has a top-level statement fails to compile when another module imports it as source, i.e. without -shared. This happens under every memory model. The error is invalid LLVM IR:

export_tl.ts:

export function twice(n: number) {
    return n * 2;
}

print("module init");

import_tl.ts:

import "./export_tl";

function main() {
    print(twice(21));
    print("done.");
}

test-runner -mm=gc import_tl.ts export_tl.ts
Global is referenced by parentless instruction!
ptr @puts
; ModuleID = 'LLVMDialectModule'
  call addrspace(0) void @puts(ptr getelementptr inbounds nuw (i8, ptr @s_..., i64 8))
tslang: error: Failed to emit LLVM IR

The result is the same under -mm=rc, and with export const k = 5; in place of the function. Removing the top-level print makes it compile. The same pair with -shared also compiles and runs.

It looks as if the imported module's top-level code is generated with no enclosing function, or into one that is then dropped. The puts call is left with no parent.

Found during -mm=own phase 6 (#445, spec §20.5).