Type checker: `store <var> as <builtin> of ...` inside an included file fails inference ('Could not infer type') — follow-on to #547

[logbie]

Summary

Follow-on to #547 (fixed in #550). The analyzer half is fixed — a stdlib call inside an included action no longer reports 'X' is not a function. But the type checker still cannot infer the type of a variable that is assigned a builtin-function result inside an included file, and it is fatal:

error[ERROR]: Type error in included file 'mod.wfl': Type error at line 2, column 5: Could not infer type for variable 'full'

Environment

• WFL 26.7.1 (main @ 1dad16a, i.e. after Fix parser, analyzer, and typechecker for documented forms and includes #550), Linux release build

Minimal reproduction

mod.wfl:

define action called h with parameters s:
    store full as wflhash256 of s
    return full
end action

main.wfl:

include from "mod.wfl"
store r as call h with "x"
display "R=" with r

wfl main.wfl →

error[ERROR]: Type error in included file 'mod.wfl': Type error at line 2, column 5: Could not infer type for variable 'full'

Also reproduces with parse_json (store p as parse_json of s) and, in my project, string_split, trim, touppercase, wflhash256_with_salt.

What works (scoping the bug)

Case	Result
store full as wflhash256 of s in an included file	❌ fatal "Could not infer type"
same line in the main file	✅ works
return substring of (wflhash256 of s) and 0 and 8 (inlined, no named var) in an included file	✅ works
store inner as call some_action with s (action-call result, not builtin) in an included file	✅ works

So it is specifically store <var> as <builtin-call> inside an included file. Inlining the builtin call (no intermediate variable) or storing an action-call result both type-check fine.

Likely cause

The #550 analyzer change taught the semantic analyzer to recognize builtins inside included files, but the type checker doesn't infer builtin return types in the include path — so a variable bound to a builtin result gets Unknown/uninferable and the type checker aborts. It probably needs the same "recognize builtins" treatment the analyzer got, applied to type inference (return-type lookup) for included files.

Impact

Any real shared library that binds a stdlib result to a variable (hashing, JSON parsing, text munging) still can't be included — the program aborts before running. Current workaround is to inline every builtin call or to concatenate sources at build time. With this fixed, include from would finally work for stdlib-using libraries end to end.

Repro test idea

Extending tests/docs_parser_and_include_fixes_test.rs: an included file with store x as wflhash256 of "a" (and a parse_json variant) called from the main program should run and type-check, not abort.