P-037 A2.2-1: decide argument relevance by value flow, not by syntax

Treatment-only (frontend/roslyn/OwnSharp.Extractor, spec/), under the frozen
taxonomy of §10.6 (F0' bb557e1). The instrument is untouched; the after-
comparison is still against R with population T.

The A2.1 producer decided whether a call was relevant by whether it could
represent the argument: a handle under a cast, an `as`, a `!`, a `?:`, a `??`
or a switch expression came out `opaque`, and the whole call record vanished.
A' (5a0de07) had already broken that coupling for params/ref/out/unstable-
owned slots; this extends the same separation to every argument shape the
freeze classifies, and does it semantically:

- BuildGuardedFacts classifies each argument's VALUE with a small walker over
  Roslyn IOperation (Classify): a built-in identity or reference conversion
  that invokes no user-defined operator is transparent (the fact is the
  unwrapped var/param); `?:`, `??`, a switch expression and an `as` the static
  type does not guarantee are may-value (relevance kept, slot opaque); a
  user-defined conversion, implicit or explicit, however spelled, is a hidden
  call and never relevance; everything else stays opaque and irrelevant.
  Conversions are read at every IConversionOperation on the path and at the
  argument's InConversion, because `(Box)r` already has type Box at the call.
- The argument operation is matched by span containment: Roslyn attaches it
  to the innermost expression (`(r)` and `r!` carry the syntax of `r`), so a
  node-identity match silently dropped exactly the transparent wrappers.
- No `mentions`: opaque is opaque (§10.6.5).

Pins:
- corpus/p037-shapes, 12 new shapes recorded with a2_expect contracts:
  transparent cast / identity cast / as-upcast / bang captured with `var s`;
  may-value conditional / coalesce / switch / as-downcast captured with an
  opaque slot; negatives userconv-implicit, userconv-explicit, cast-nonhandle
  and mayvalue-userconv-arm carry no guarded_facts at all. The 14 existing
  shapes, the three A' relevance witnesses included, are byte-identical.
- corpus/p037-relevance/probe: a2_2_1_observed measured with this walker;
  exactly the eight transparent and may-value rows moved to sidecar_call,
  every other row reads as at A'. tests/test_p037_relevance_freeze.py pins
  that (indirect rows never captured; direct and call-like rows unmoved; no
  captured row lost).
- scripts/p037_sidecar_inertness.py: 27 documents, 59 sidecars, inert on
  both engines, python == rust. spec/OwnIR.md §5.2 states the value-flow rule.

Refs #304

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QfeUtLRm6KFRWcTGQZxQQb

Author: claude

corpus/p037-relevance/README.md

@@ -41,6 +41,9 @@ row into a checked `captured` / `excluded_by_rule:<name>` assertion.
 
 ## What moves this census
 
+A2.2-1 landed: the eight transparent and may-value rows read `sidecar_call` in
+`a2_2_1_observed`, measured with the walker; every other row reads as at A'.
+
 Only an A2.2 step, deliberately, one row at a time: a transparent wrapper
 becomes `captured` in A2.2-1, a call-like form in A2.2-2, an orphan record
 appears in A2.2-3. A row that moves without a step meaning to move it is a

corpus/p037-relevance/probe/expected.json

@@ -4,6 +4,7 @@
   "why": "One method per argument shape through which a disposable local can reach a callee, with the conversion edge on the way. Each is classified against the frozen taxonomy; `a2_1_observed` records what the corrected A2.1 extractor (A') emitted for it, measured, not assumed, so the A2.2 steps move a named row, never a number.",
   "observed_at": "5a0de070af241a2612859153887ad6ae04afcce2",
   "observed_at_note": "A' = corrected A2.1 treatment (PR #363), landed via main@23e3203; the extractor is byte-identical between A' and that merge. The superseded A (dce26ed) is not a measurement point.",
+  "a2_2_1_note": "Measured with the A2.2-1 extractor (the IOperation value-flow walker) from the tree this file is committed in, before the commit: the SHA that carries this file is the SHA it was measured at. A2.2-1 promises exactly the transparent and may-value rows move to sidecar_call; every other row must read as it did at A'.",
   "observed_vocabulary": {
     "sidecar_call": "a function record with a guarded_facts call fact for the probe call",
     "record_without_call_fact": "a function record exists but carries no call fact for the probe call",
@@ -27,155 +28,180 @@
     "Plain": {
       "class": "direct",
       "conversion": "reference_upcast",
-      "a2_1_observed": "sidecar_call"
+      "a2_1_observed": "sidecar_call",
+      "a2_2_1_observed": "sidecar_call"
     },
     "PlainSame": {
       "class": "direct",
       "conversion": "none",
       "note": "identity binding to a NON-consuming callee: the legacy pass reads the pass as an escape, no tracked local remains, no record at all; the orphan carrier's case (\u00a710.6.6), and a direct flow",
-      "a2_1_observed": "no_record"
+      "a2_1_observed": "no_record",
+      "a2_2_1_observed": "no_record"
     },
     "Parens": {
       "class": "transparent",
       "wrapper": "parenthesized",
       "conversion": "reference_upcast",
-      "a2_1_observed": "sidecar_call"
+      "a2_1_observed": "sidecar_call",
+      "a2_2_1_observed": "sidecar_call"
     },
     "IdentityCast": {
       "class": "transparent",
       "wrapper": "cast",
       "conversion": "identity",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "sidecar_call"
     },
     "Cast": {
       "class": "transparent",
       "wrapper": "cast",
       "conversion": "reference_upcast",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "sidecar_call"
     },
     "AsCast": {
       "class": "transparent",
       "wrapper": "as",
       "conversion": "reference_upcast",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "sidecar_call"
     },
     "Bang": {
       "class": "transparent",
       "wrapper": "null_forgiving",
       "conversion": "reference_upcast",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "sidecar_call"
     },
     "Ternary": {
       "class": "may_value",
       "form": "conditional",
       "conversion": "reference_upcast",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "sidecar_call"
     },
     "Coalesce": {
       "class": "may_value",
       "form": "null_coalescing",
       "conversion": "reference_upcast",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "sidecar_call"
     },
     "Switch": {
       "class": "may_value",
       "form": "switch_expression",
       "conversion": "reference_upcast",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "sidecar_call"
     },
     "AsMayFail": {
       "class": "may_value",
       "form": "as_may_fail",
       "conversion": "may_fail_null",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "sidecar_call"
     },
     "Ctor": {
       "class": "call_like",
       "form": "object_creation",
       "conversion": "reference_upcast",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "record_without_call_fact"
     },
     "DelegateCall": {
       "class": "call_like",
       "form": "delegate_invocation",
       "conversion": "reference_upcast",
-      "a2_1_observed": "no_record"
+      "a2_1_observed": "no_record",
+      "a2_2_1_observed": "no_record"
     },
     "Nested": {
       "class": "indirect",
       "exclusion": "nested_call_result",
       "conversion": "not_applicable",
       "note": "Wrap(r) itself is direct and is owed its own call fact; Use receives call_result",
-      "a2_1_observed": "no_record"
+      "a2_1_observed": "no_record",
+      "a2_2_1_observed": "no_record"
     },
     "ArrayInit": {
       "class": "indirect",
       "exclusion": "container_construction",
       "conversion": "not_applicable",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "record_without_call_fact"
     },
     "CollectionInit": {
       "class": "indirect",
       "exclusion": "container_construction",
       "conversion": "not_applicable",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "record_without_call_fact"
     },
     "Tuple": {
       "class": "indirect",
       "exclusion": "tuple_construction",
       "conversion": "not_applicable",
-      "a2_1_observed": "no_record"
+      "a2_1_observed": "no_record",
+      "a2_2_1_observed": "no_record"
     },
     "Closure": {
       "class": "indirect",
       "exclusion": "closure_capture",
       "conversion": "not_applicable",
       "note": "the inner Use(r) belongs to the lambda body, which has no record of its own (known gap)",
-      "a2_1_observed": "no_record"
+      "a2_1_observed": "no_record",
+      "a2_2_1_observed": "no_record"
     },
     "MethodGroup": {
       "class": "indirect",
       "exclusion": "method_group_conversion",
       "conversion": "not_applicable",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "record_without_call_fact"
     },
     "UserConversion": {
       "class": "indirect",
       "exclusion": "user_conversion",
       "conversion": "user_defined_implicit",
       "note": "syntactically a bare identifier; only the semantic model shows the hidden op_Implicit",
-      "a2_1_observed": "no_record"
+      "a2_1_observed": "no_record",
+      "a2_2_1_observed": "no_record"
     },
     "ExplicitUserConversion": {
       "class": "indirect",
       "exclusion": "user_conversion",
       "conversion": "user_defined_explicit",
       "note": "syntactically a cast; the user-defined operator sits inside the cast expression, and (XBox)r already has type XBox at the call",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "record_without_call_fact"
     },
     "NameOf": {
       "class": "indirect",
       "exclusion": "nameof_operand",
       "conversion": "not_applicable",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "record_without_call_fact"
     },
     "MemberAccess": {
       "class": "indirect",
       "exclusion": "member_access_on_handle",
       "conversion": "not_applicable",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "record_without_call_fact"
     },
     "Receiver": {
       "class": "indirect",
       "exclusion": "receiver_not_summary_parameter",
       "conversion": "not_applicable",
-      "a2_1_observed": "record_without_call_fact"
+      "a2_1_observed": "record_without_call_fact",
+      "a2_2_1_observed": "record_without_call_fact"
     },
     "Indexer": {
       "class": "indirect",
       "exclusion": "storage_assignment",
       "conversion": "not_applicable",
-      "a2_1_observed": "no_record"
+      "a2_1_observed": "no_record",
+      "a2_2_1_observed": "no_record"
     }
   }
 }

corpus/p037-shapes/sidecar-cast-nonhandle/case.cs

@@ -0,0 +1,15 @@
+using System;
+using System.IO;
+
+// A2.2-1 NEGATIVE: a transparent wrapper around a NON-handle creates no relevance. The cast
+// unwraps to a static property, which is opaque and not a handle of this method.
+static class ShapeCastNonHandle
+{
+    static void Inner(Stream s, bool leaveOpen) { if (!leaveOpen) s.Dispose(); }
+    static void Caller(string path)
+    {
+        var keep = File.OpenRead(path);
+        Inner((Stream)Stream.Null, true);
+        keep.Dispose();
+    }
+}

corpus/p037-shapes/sidecar-cast-nonhandle/expected.json

@@ -0,0 +1,53 @@
+{
+  "schema": "p037-fact-shape/1",
+  "shape": "sidecar-cast-nonhandle",
+  "status": "anchored",
+  "why": "P-037 A2.2-1 (formal note §10.6.3): negative: a cast around a non-handle is not relevance; no call fact. Recorded with the IOperation value-flow walker; a row that moves without a step meaning to move it is a regression.",
+  "a2_expect": [
+    {
+      "function": "ShapeCastNonHandle.Caller",
+      "guarded_facts": "absent"
+    }
+  ],
+  "facts": {
+    "ShapeCastNonHandle.Inner": {
+      "params": [
+        {
+          "name": "s",
+          "line": 8
+        }
+      ],
+      "body": [
+        "if:None@8",
+        "then:release:s@8"
+      ],
+      "guarded_facts": {
+        "version": 1,
+        "calls": [],
+        "guards": [
+          {
+            "site": {
+              "line": 8,
+              "column": 51
+            },
+            "param": 1,
+            "predicate": "truth",
+            "negated": true
+          }
+        ]
+      }
+    },
+    "ShapeCastNonHandle.Caller": {
+      "params": null,
+      "body": [
+        "acquire:keep@11",
+        "release:keep@13"
+      ],
+      "guarded_facts": null
+    }
+  },
+  "verdict": {
+    "rust": [],
+    "python": []
+  }
+}

corpus/p037-shapes/sidecar-mayvalue-as-downcast/case.cs

@@ -0,0 +1,14 @@
+using System;
+using System.IO;
+
+// A2.2-1: `s as FileStream` on a Stream-typed handle is NOT guaranteed by the static type: it
+// yields the handle or null. May-value: relevant, opaque slot (contrast sidecar-transparent-as-upcast).
+static class ShapeMayValueAsDowncast
+{
+    static void InnerF(FileStream f, bool leaveOpen) { if (!leaveOpen) f.Dispose(); }
+    static void Caller(string path)
+    {
+        Stream s = File.OpenRead(path);
+        InnerF(s as FileStream, true);
+    }
+}