v3: keep same-named types from using str methods of other modules

[medvednikov]

Summary

A program importing both toml and x.json2 failed to compile with V3:

import toml
import x.json2

struct TestStruct {
	key string
}

fn main() {
	t := toml.decode[TestStruct]('key = "val"')!
	println(t.str())
	println(json2.encode[TestStruct](t))
}

src.c: error: initializing 'json2__Any' with an expression of incompatible type 'toml__Any'
    json2__Any __return_array_value_8 = *(toml__Any*)(array_get(__return_array_5, __return_array_idx_7));

Root cause: toml.Any.string() falls back to a.str(), which stringifies the []Any variant. Method lookup then consults receiver_method_suffix_index, which is keyed by short receiver spellings ([]Any.str, Any.str). Only json2 declares such methods, so []toml.Any resolved to json2.[]Any.str and the transformer emitted an element-copy conversion from []toml.Any to []json2.Any. The same lookup also let bmod.Any pick amod.Any.str, and made an explicit toml_array.str() fail in the checker with cannot use receiver `[]toml.Any` as `[]json2.Any` .

Fix:

• types: suffix_indexed_method_fits_receiver rejects a suffix-index hit when it was declared in a different module from the receiver's struct, sum type or enum. Arrays and maps are checked by their element/value type. The check applies in concrete_method_signature_key and in the checker's unique_receiver_method_suffix_match callers. Aliases, interfaces and structs with embedded fields keep the old lookup, because they can legitimately inherit methods declared in other modules (e.g. an embedded veb.Context).
• transform: resolve_receiver_method_for_type applies the same check to its suffix match and to the declared_receiver_method fallback. The fallback is only rejected when the index shows another module registered the method. Bare receiver types declared in the current module (Any inside toml) are qualified before asking the checker, so they don't resolve through a stale checker module.

Validation

• New vlib/v/tests/same_name_types_str_methods/:
  • Local modules withstr and nostr mirror json2.Any and toml.Any. The test covers sum type, array, map, struct and enum stringification (.str(), interpolation, a module-side .str() fallback).
  • toml_and_json2_test.v is the reported program.
  • Both fail on master (checker error / C compile error) and pass with this change.
• ./v -silent test vlib/v/transform/: 17/17 pass.
• ./v -silent test vlib/toml/ vlib/json2/: 106 passed, 1 skipped.
• ./v -silent test vlib/v/types/: 30/31 pass. checker_ownership_alias_test.v hangs in the -d ownership prescan on master too, in other checkouts as well.
• ./v -silent vlib/v/compiler_errors_test.v: 1720 passed. The one failure, anon_struct_private_field_err, also fails on master.
• ./v -silent test vlib/v/tests/: 2285 passed, 13 failed. All 13 fail the same way on master: builtin_overflow_test, check_in_is_consistency_test, enum_bitfield_test, enum_from_generic_static_method_test, failing_tests_test, fn_call_mut_ref_args_test, fn_with_opt_or_res_of_multi_return_test, for_in_containers_of_fixed_array_test, for_in_ref_arr_test, struct_aligned_test, struct_heap_large_fixed_array_test, vls/goto_def_test, vls/autocomplete_module_test.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-24T12:41:15.800652Z	3df0eda	Manual request

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[medvednikov]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Breezy!

Reviewed commit: 3df0edaea0

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