Add CI check comparing @specs against inferred type signatures

make check_specs runs lib/elixir/scripts/compare_specs_and_signatures.exs,
which translates stdlib @SPEC declarations into Module.Types.Descr types
and compares them against the compiler-inferred signatures (ExCk chunk)
with semantic subtyping, slice-wise per spec clause. Residue that cannot
be auto-triaged is executed against concrete witnesses (rejection-sampled
in-domain values plus doctest-mined calls) in sandboxed tasks.

The gate fails on witness-proven findings, lattice contradictions, and
any divergence not acknowledged in compare_specs_exclusions.txt; stale
exclusions only warn. Witness sampling is PRNG-seeded so runs are
deterministic on a given build. Wired into the deterministic CI matrix
entry, ~11s per run.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: lukaszsamson

.github/workflows/ci.yml

@@ -97,6 +97,10 @@ jobs:
           name: TestCoverage
           path: cover/*
 
+      - name: Check specs vs inferred type signatures
+        if: ${{ matrix.deterministic }}
+        run: make check_specs
+
       - name: Check reproducible builds
         if: ${{ matrix.deterministic }}
         run: taskset 1 make check_reproducible

Makefile

@@ -26,7 +26,7 @@ GIT_TAG = $(strip $(shell head="$(call GIT_REVISION)"; git tag --points-at $$hea
 SOURCE_DATE_EPOCH_PATH = lib/elixir/tmp/ebin_reproducible
 SOURCE_DATE_EPOCH_FILE = $(SOURCE_DATE_EPOCH_PATH)/SOURCE_DATE_EPOCH
 
-.PHONY: cover install install_man build_plt clean_plt dialyze test check_reproducible clean clean_elixir clean_man format docs Docs.zip Precompiled.zip zips
+.PHONY: cover install install_man build_plt clean_plt dialyze test check_reproducible check_specs clean clean_elixir clean_man format docs Docs.zip Precompiled.zip zips
 .NOTPARALLEL:
 
 #==> Functions
@@ -141,6 +141,11 @@ install: compile
 	done
 	"$(MAKE)" install_man
 
+check_specs: compile
+	$(Q) echo "==> Checking @specs against inferred type signatures..."
+	$(Q) bin/elixir lib/elixir/scripts/compare_specs_and_signatures.exs \
+	     --exclusions lib/elixir/scripts/compare_specs_exclusions.txt
+
 check_reproducible: compile
 	$(Q) echo "==> Checking for reproducible builds..."
 	$(Q) rm -rf lib/*/tmp/ebin_reproducible/