v3: parse pointer-bearing generic args like Foo[fn (&T) int] as type args

[medvednikov]

Summary

is_fixed_array_len_text decides whether the text inside Base[...] is a fixed-array length or a generic type argument. It treated any & after the first character as a bitwise-and length operator. So foo.Foo[fn (&Baz) int] was read as a fixed array of foo.Foo with length fn (&Baz) int, and field access failed with error: `[fn (&Baz) int]foo.Foo` has no property `value` . Fn-field calls through it became unknown functions. This happened in every context (globals, locals, struct fields, params), and also for Foo[[]&T], Foo[map[K]&T], Foo[?&T], Foo[&&T], Foo[Box[&T]], Foo[chan &T] and Foo[fn () &T].

The checker now:

• never treats argument text that starts with type-only syntax (&, ?, !, [, ..., map[, fn, chan, thread, shared, atomic, mut) as a length;
• ignores &/- nested inside brackets.

The transform and cgen typeof helpers share the same heuristic. They get the same &/?/! prefix check, so ?&T and &&T instances are not mangled as fixed arrays later on.

The alias form from the report (type Bar = fn (&Baz) int, __global global_value foo.Foo[Bar]) already compiles and runs correctly on current master. foo__Foo_fn_ptr_Baz_int__set, the function the report says is missing, is the name V3 gives the inline instance's set method.

Fixes #28884

Validation

• New vlib/v/tests/generic_fn_ptr_arg_28884/ covers:

  • the alias and inline fn-type globals;
  • locals, a struct field and a mut param;
  • named-param and pointer-returning fn types;
  • the nested pointer forms above.

  It stores real fns and calls them through the containers. 1/1 passed; it fails on master.

• ./v -silent vlib/v/compiler_errors_test.v: 1720 passed, 1 failed (modules/anon_struct_private_field_err, same failure on master)

• ./v -silent test vlib/v/gen/c/: 27/27 passed

• ./v -silent test vlib/v/tests/generics/: 321/321 passed

• ./v -silent test vlib/v/transform/: 17/17 passed

• ./v -silent test vlib/v/types/: 30 passed; checker_ownership_alias_test.v hangs, as it does on master (V3: checker_ownership_alias_test.v never finishes compiling (-d ownership compiler spins at 100% CPU) #28923)

• typeof, fixed-array and __global tests in vlib/v/tests: 42/42 passed

[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 2026-09-24T12:41:40.824690Z	cbd9c57	PR opened

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