BFM-decomp/cookbook/C0125.md

§114 — The THIRD decl axis: a CALLEE the draft declares differently from the target TU (Phase 29 T76/T77)

Three axes can make a templated family draft fail conflicting types, and the sweep pipeline handled only two of them:

axis	whose signature	lever
the draft's own definition	func_X itself vs the shared header	reconcile_def_sig (§109)
DATA externs	D_XXXX	scope_data_externs (§8d) + scope_tu_externs (§103)
a CALLEE	func_Y that the draft calls	cast_call_sites (§17a-1/§20) — was not in the pipeline

The third axis was the whole reason the byte-identical family tier measured 0 of 682 (T76). Three independent diagnoses had already named it and none of them was the family's own function:

func_80173A60 -> conflicting types for func_80173B4C    (a callee)
func_8012F40C -> conflicting types for RotTransPers     (a PsyQ LIBRARY symbol)
0x80143d28    -> conflicting types for ApplyMatrixSV    (likewise)

cast_call_sites already solves exactly this — rewrite the callee's decl to the TU's canonical signature (killing the in-TU conflict while keeping the symbol in scope) and cast each call site back to the draft's intended signature; gcc folds the cast of a known symbol to a direct jal, so it is codegen-neutral. It lived only in gate_stage, which the family sweep deliberately does not use (§T3: gate_stage's transforms perturb a correct remapped draft). Wiring it into the sweep took func_80173A60 from 0/135 to 135/135.

Two details that matter when wiring it:

• Build the canonical map from the TARGET sibling's TU, via cpp (canonical_map(ov, src_file=tu) → cdecl.tu_scope). A raw-text scan cannot see a macro-injected declaration, and engine_core.h is ~23.5k continuation lines inside ~1,800 macros — so the map would return nothing for exactly the callees that conflict (§51g LAW 7).
• Read the TU after any TU-side edit is on disk, so the map reflects the environment the draft will actually meet.

The law: conflicting types for X — read X. When X is not the function being templated, no amount of work on the definition's signature or the shared header will help, and both will look like plausible next steps. Three diagnoses named a callee before anyone checked whether the pipeline could act on one.

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