Move the pure protocol/impl conformance lookups into one module,
src/ir/protocols.zig, behind a *Lowering facade (ProtocolResolver), mirroring
GenericResolver / CallResolver. Per PLAN-ARCH A4.2 ("move pure lookup first;
keep emission in Lowering"), this increment moves only the read-only queries:
- getProtocolInfo (is a type a registered protocol + its method table),
- hasImplPlain (have the (protocol, type) thunks been materialized),
- packArgConformsTo (impl-declaration-level conformance for ..xs: P).
Registration (registerProtocolDecl / registerImplBlock / registerParamImpl) and
all IR emission (createProtocolThunk / buildProtocolValue / tryUserConversion /
getOrCreateThunks) stay in Lowering for the later increments. The state maps
(protocol_thunk_map / param_impl_map on Lowering, protocol_decl_map /
protocol_ast_map in ProgramIndex) stay put; the facade reads them via self.l.* —
no map migration.
Lowering keeps getProtocolInfo as a thin pub wrapper (~9 callers incl.
calls.zig); hasImplPlain + packArgConformsTo are deleted (no fallback), their 3
call sites (computeHasImpl x2, the pack-conformance check x1) routed through
self.protocolResolver(). formatTypeName widened to pub (the lookups use it);
protocolResolver() accessor added.
protocols.test.zig (wired into the barrel) drives ProtocolResolver directly:
getProtocolInfo (registered vs builtin/plain-struct + wrapper delegation),
hasImplPlain (thunk-map materialization), packArgConformsTo (non-parameterised
requires <ty>.<m> in fn_ast_map; trivially-true for an erased protocol value;
false for unknown protocol).
zig build, zig build test, tests/run_examples.sh (357/0) all green — no .ir
snapshot churn; the 0410/0411/0412 rejection anchors still pass.
