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+# Fallback-zero verification (Stage 1 Task 3).
+#
+# self-host-test.janet checks observable RESULTS but not WHICH path ran — a form
+# that silently fell back to the interpreter still "passes" there. This harness
+# checks the path: it runs the portable analyzer (jolt.analyzer/analyze, via
+# backend/analyze-form) on a corpus of NON-STATEFUL forms and asserts NONE raise
+# :jolt/uncompilable — i.e. the self-hosted analyzer actually COMPILED them.
+#
+# As analyzer↔compiler.janet parity grows (Stage 1), move forms from the
+# "intentional fallback" sanity list into the must-compile corpus. The day the
+# fallback set equals the frozen intentional stateful set, the Janet bootstrap
+# compiler is retireable.
+#
+# Mechanism: backend/analyze-form throws (a "jolt/uncompilable: …" string) for a
+# punted form; (protect …) turns that into [false msg]. [true ir] == compiled.
+
+(import ../../src/jolt/backend :as backend)
+(use ../../src/jolt/api)
+(use ../../src/jolt/reader)
+
+(def ctx (init))
+
+(defn- analyzes? [s]
+  # true if the analyzer produced IR (compiled), false if it punted/uncompilable.
+  (def r (protect (backend/analyze-form ctx (parse-string s))))
+  (and (r 0) true))
+
+# --- Must compile: pure, non-stateful value production. NONE may punt. ---
+(def must-compile
+  [# set literals (Task 1)
+   "#{1 2 3}" "#{}" "#{:a :b :c}" "#{(inc 0) 2}" "(conj #{1 2} 3)"
+   "[#{1 2} {:s #{3}}]" "(let [x 5] #{x (inc x)})"
+   # other literals
+   "[1 2 3]" "{:a 1 :b 2}" "{:k (inc 0)}" "[[1] [2 3]]" "42" ":kw" "\"str\""
+   # control flow + binding
+   "(+ 1 2)" "(if true 1 2)" "(do 1 2 3)" "(let [a 1 b 2] (+ a b))"
+   "(fn [x] (* x x))" "(fn ([a] a) ([a b] (+ a b)))"
+   "(loop [i 0] (if (< i 3) (recur (inc i)) i))"
+   "(quote (a b c))" "(throw (ex-info \"x\" {}))"
+   "(try (inc 1) (catch :default e e))"
+   # def + calls into core
+   "(def answer 42)" "(map inc [1 2 3])" "(reduce + 0 [1 2 3])"
+   "(get {:a 1} :a)" "(vec (range 5))"])
+
+# --- Intentional fallback (sanity sample): these SHOULD punt to the interpreter.
+# Not the frozen set (that's Task 2) — just a few to confirm the boundary holds
+# in the punt direction so the harness can't pass by compiling everything.
+(def must-punt
+  ["(ns foo.bar)" "(defmacro m [x] x)" "(require (quote [clojure.string]))"
+   "(set? #{1 2})" "(letfn [(f [n] (g n)) (g [n] (f n))] (f 1))"])
+
+(var fails @[])
+(each s must-compile
+  (unless (analyzes? s) (array/push fails (string "FALLBACK (should compile): " s))))
+(each s must-punt
+  (when (analyzes? s) (array/push fails (string "COMPILED (should punt): " s))))
+
+(printf "fallback-zero: %d must-compile + %d must-punt — %d failures"
+        (length must-compile) (length must-punt) (length fails))
+(when (> (length fails) 0)
+  (print "\nFailures:")
+  (each f fails (printf "  %s" f))
+  (os/exit 1))
+(print "fallback-zero: OK (analyzer compiled the full non-stateful corpus)")