t27b: a bench's _ = e; is a discard; ternary_gates' benches type-check once referenced (Closes #8546)

.trinity/seals/TernaryGates.json

@@ -1,12 +1,12 @@
 {
-  "gen_hash_c": "sha256:608e9f52b077faf20ba1e274f02a386bb48f27767c878ec5683567bd5b6a755d",
+  "gen_hash_c": "sha256:87ac584ac4d46a1011b6ebcdc8bda48bd7b578e7f34a6f8df1942c0b12a5a247",
   "gen_hash_rust": "sha256:d50d3454f51312df8ae97f8885d1ef89eccf26835aab641ec4a7d131a94556a4",
   "gen_hash_verilog": "sha256:a0ecc024bbf108bf40c663321efaadc401dc9e22f8d45323eae4913dc08738bc",
-  "gen_hash_zig": "sha256:50a48d04ba20fe714abc08eeeba6821801b1db40bce026966670030291dc4819",
+  "gen_hash_zig": "sha256:d9602a0e9c3228201cb27c2a83f47a149871059fbfb3c7fa1b73ec47eda8cbcf",
   "module": "TernaryGates",
   "ring": 12,
-  "sealed_at": "2026-10-10T12:32:59Z",
-  "spec_hash": "sha256:48513ed8f9c995547a1b374a3c09c7ac428c9a11b40834a78e75028b956903ca",
+  "sealed_at": "2026-10-10T13:36:51Z",
+  "spec_hash": "sha256:94fc7637fe4d830a624d700ad231075159fdaed1a79b0d605a5bdacb38083b0c",
   "spec_path": "specs/isa/ternary_gates.t27",
   "tests": {
     "failed": 0,

.trinity/seals/isa_TernaryGates.json

@@ -1,22 +1,22 @@
 {
-  "built_by": "t27c-bootstrap@0.5.2+c494cc5",
+  "built_by": "t27c-bootstrap@0.5.2+3c0ae4d49",
   "closure": [
     {
       "spec": "specs/base/types.t27",
       "spec_hash": "sha256:9d02d8b1016993658e1e9748e4bc13bc4f3732535c16e3484abdaeeafcf608bc"
     }
   ],
   "config": "gen=c,rust,verilog,zig;tests=zig",
-  "gen_hash_c": "sha256:608e9f52b077faf20ba1e274f02a386bb48f27767c878ec5683567bd5b6a755d",
+  "gen_hash_c": "sha256:87ac584ac4d46a1011b6ebcdc8bda48bd7b578e7f34a6f8df1942c0b12a5a247",
   "gen_hash_rust": "sha256:d50d3454f51312df8ae97f8885d1ef89eccf26835aab641ec4a7d131a94556a4",
   "gen_hash_verilog": "sha256:a0ecc024bbf108bf40c663321efaadc401dc9e22f8d45323eae4913dc08738bc",
-  "gen_hash_zig": "sha256:50a48d04ba20fe714abc08eeeba6821801b1db40bce026966670030291dc4819",
+  "gen_hash_zig": "sha256:d9602a0e9c3228201cb27c2a83f47a149871059fbfb3c7fa1b73ec47eda8cbcf",
   "module": "TernaryGates",
   "ring": 12,
   "seal_schema": 2,
-  "sealed_at": "2026-10-10T12:32:59Z",
+  "sealed_at": "2026-10-10T13:36:51Z",
   "sealed_by": "t27c-bootstrap@0.5.2",
-  "spec_hash": "sha256:48513ed8f9c995547a1b374a3c09c7ac428c9a11b40834a78e75028b956903ca",
+  "spec_hash": "sha256:94fc7637fe4d830a624d700ad231075159fdaed1a79b0d605a5bdacb38083b0c",
   "spec_path": "specs/isa/ternary_gates.t27",
   "tests": {
     "failed": 0,

.trinity/seals/t27b_T27bDiscardPlan.json

@@ -1,24 +1,24 @@
 {
-  "built_by": "t27c-bootstrap@0.5.2+5d5d2cdef",
+  "built_by": "t27c-bootstrap@0.5.2+3c0ae4d49",
   "closure": [],
   "config": "gen=c,rust,verilog,zig;tests=zig",
-  "gen_hash_c": "sha256:95bdef51d7d83ec98fd1df0adbb7dd26ba707b33e2bc13dcadbd7c75857ed19f",
-  "gen_hash_rust": "sha256:1a068c18c77ef1bb3a34f116501b6c794ded4b50086c1d867f1c0e7f72ebf869",
-  "gen_hash_verilog": "sha256:48ffbb7235fbdb556a2d06f9f9d920c88daa31b1087c956a4d933eeecbc7df97",
-  "gen_hash_zig": "sha256:59c5b80da21ff3c327b46ee14bce77bb445604eae90e2362695b8058dc001a6a",
+  "gen_hash_c": "sha256:c9fdbc89627e959585ccc9a35b15953f241aabe076af0bfe307b3c5e3d87bc43",
+  "gen_hash_rust": "sha256:4651655a9576deecffd83b5cbb135703587e3d711d707a24a99ea79b51a5dc52",
+  "gen_hash_verilog": "sha256:c9fc6a3d44087796ad3f96e53227faf9755babf5a3cb8dce76fc688ba8944140",
+  "gen_hash_zig": "sha256:e984cd161839534c3a1fe6159e0d6b298b89a4d151f1134e523daae68c3f8e2a",
   "module": "T27bDiscardPlan",
   "ring": 12,
   "seal_schema": 2,
-  "sealed_at": "2026-10-09T14:58:35Z",
+  "sealed_at": "2026-10-10T13:36:52Z",
   "sealed_by": "t27c-bootstrap@0.5.2",
-  "spec_hash": "sha256:f255459b0b4e1feb33373c09a9e1fb1c7368796cc261177db4dc6613b5c3881d",
+  "spec_hash": "sha256:f136521731ed02abfe8e7d04578f3407479efcca16e3054998728880d3778491",
   "spec_path": "specs/tri/t27b/discard_plan.t27",
   "tests": {
     "failed": 0,
     "failing": [],
     "forced": false,
-    "passed": 4,
-    "total": 4
+    "passed": 6,
+    "total": 6
   },
   "toolchain": {
     "test_runner": "sha256:1982ae948e24d00c5d221ccec12dfce1eb01204b53e37b0f857f93b16d64629d",

cli/t27b/src/lower.rs

@@ -2523,7 +2523,7 @@ impl<'a> Lower<'a> {
         if name == "_" && (op.is_empty() || op == "=") {
             let (mut calls, top) = (Vec::new(), self.scopes.len() == 1);
             calls_in(std::slice::from_ref(rhs), &mut calls);
-            match dp::plan(rhs.kind == NodeKind::ExprIdentifier, self.in_test && top, !self.in_test && top, !calls.is_empty()) {
+            match dp::plan(rhs.kind == NodeKind::ExprIdentifier, self.in_test && top, self.in_bench, !self.in_test && top, !calls.is_empty()) {
                 dp::DELETED => return Ok(()),
                 dp::EVALUATE => return self.discard_value(rhs, out),
                 _ => {}

docs/now/2026-10-10-t27b-bench-discards-and-ternary-gates-benches.md

@@ -0,0 +1,7 @@
+# NOW -- t27b: a bench's `_ = e;` is a discard; ternary_gates' benches type-check once referenced (2026-10-10)
+
+## t27b blocker after c7570433e (Closes #8546; see #8195)
+
+- arty_a7_integration.t27: its bench discards a u32, a u32, then a bool at the top level. t27b's test-binding path bound `_` as a u32 variable and refused the bool (`type mismatch`). t27c prints each one as Zig's `_ = e;`. specs/tri/t27b/discard_plan.t27 now evaluates and drops every `_ = e;` at the top of a bench. The glue changes one line.
+- ternary_gates.t27: t27b was right. Once a test calls the benches, zig 0.16 refuses them three ways: signed `%`, an i32 into a u32, and a run-time index into a tuple. The spec now uses a `[3]i32` array and `@intCast(result + 1)`. With a test that calls all four benches, the reference passes 13/13.
+- t27b `test --check` passes both specs: 12/12 with 122 asserts and 6/6 with 13. Both ledger rows are back to pass, and max_not_pass goes from 27 to 25.

docs/reports/t27b_expectations.json

@@ -12,7 +12,7 @@
   "reference-bug": "the reference passes it for the wrong reason; t27b is right not to",
   "n/a": "outside what t27b is for (say why in the PR that sets it)"
  },
- "max_not_pass": 27,
+ "max_not_pass": 25,
  "entries": [
   {"path": "specs/a/b_c.t27", "t27b": "pass"},
   {"path": "specs/a_b/c.t27", "t27b": "pass"},
@@ -263,7 +263,7 @@
   {"path": "specs/docs/system.t27", "t27b": "pass"},
   {"path": "specs/fpga/adapter.t27", "t27b": "pass"},
   {"path": "specs/fpga/assembler.t27", "t27b": "pass"},
-  {"path": "specs/fpga/boards/arty_a7_integration.t27", "t27b": "blocked", "blocker": "type mismatch", "reason": "unimplemented"},
+  {"path": "specs/fpga/boards/arty_a7_integration.t27", "t27b": "pass"},
   {"path": "specs/fpga/boards/qmtech_a100t_integration.t27", "t27b": "pass"},
   {"path": "specs/fpga/bootrom.t27", "t27b": "pass"},
   {"path": "specs/fpga/bpsk.t27", "t27b": "pass"},
@@ -355,7 +355,7 @@
   {"path": "specs/isa/t27a.t27", "t27b": "pass"},
   {"path": "specs/isa/t27a_mnemonics.t27", "t27b": "pass"},
   {"path": "specs/isa/ternary_encoding.t27", "t27b": "pass"},
-  {"path": "specs/isa/ternary_gates.t27", "t27b": "blocked", "blocker": "type mismatch", "reason": "unimplemented"},
+  {"path": "specs/isa/ternary_gates.t27", "t27b": "pass"},
   {"path": "specs/isa/ternary_graph.t27", "t27b": "pass"},
   {"path": "specs/isa/tri27_bytecode.t27", "t27b": "pass"},
   {"path": "specs/isa/tri27_machine.t27", "t27b": "pass"},

gen/rust/tri/t27b/discard_plan.rs

@@ -1,6 +1,6 @@
 // Generated from .t27 spec
 // DO NOT EDIT — generated by t27c
-// NOT LOWERED BY THIS BACKEND: 4 test(s), 0 invariant(s), 0 function(s) with no body.
+// NOT LOWERED BY THIS BACKEND: 6 test(s), 0 invariant(s), 0 function(s) with no body.
 // This backend emits declarations only. The spec's checks live in
 // the Zig and Verilog outputs; do not read this file as verified.
 
@@ -10,11 +10,11 @@ pub const DELETED: u8 = 1;
 
 pub const EVALUATE: u8 = 2;
 
-pub fn plan(name: bool, test_top: bool, fn_top: bool, call: bool) -> u8 {
+pub fn plan(name: bool, test_top: bool, in_bench: bool, fn_top: bool, call: bool) -> u8 {
     if name {
         return NOT_MINE;
     }
-    if test_top {
+    if (test_top && !(in_bench)) {
         return NOT_MINE;
     }
     if (fn_top && !(call)) {

specs/isa/ternary_gates.t27

@@ -372,33 +372,33 @@ module TernaryGates {
     bench ternary_min_performance
         // Measure: cycles to compute 1000 MIN operations
         // Target: < 1000 cycles
-        const vals = [_]i32{TRIT_NEG, TRIT_ZERO, TRIT_POS};
+        const vals : [3]i32 = [_]i32{TRIT_NEG, TRIT_ZERO, TRIT_POS};
         var result : i32 = 0;
         var i : u32 = 0;
         while i < 1000 {
-            var idx : u32 = (result + 1) % 3;
-            result = ternary_min(result, vals[idx]);
+            const idx : u32 = @intCast(result + 1);
+            result = ternary_min(result, vals[idx % 3]);
             i = i + 1;
         }
         _ = result;
 
     bench ternary_max_performance
         // Measure: cycles to compute 1000 MAX operations
         // Target: < 1000 cycles
-        const vals = [_]i32{TRIT_NEG, TRIT_ZERO, TRIT_POS};
+        const vals : [3]i32 = [_]i32{TRIT_NEG, TRIT_ZERO, TRIT_POS};
         var result : i32 = 0;
         var i : u32 = 0;
         while i < 1000 {
-            var idx : u32 = (result + 1) % 3;
-            result = ternary_max(result, vals[idx]);
+            const idx : u32 = @intCast(result + 1);
+            result = ternary_max(result, vals[idx % 3]);
             i = i + 1;
         }
         _ = result;
 
     bench ternary_consensus_performance
         // Measure: cycles to compute 1000 CONSENSUS operations
         // Target: < 2000 cycles
-        const vals = [_]i32{TRIT_NEG, TRIT_ZERO, TRIT_POS};
+        const vals : [3]i32 = [_]i32{TRIT_NEG, TRIT_ZERO, TRIT_POS};
         var result : i32 = 0;
         var idx : u32 = 0;
         var i : u32 = 0;

specs/tri/t27b/discard_plan.t27

@@ -16,14 +16,19 @@
 ;     `if` traps), and drops the value, void or not.
 ;   - At the top level of a test, t27c's test-binding form prints `const _ = e;`, and Zig refuses it ("'_' used
 ;     as an identifier without @"_" syntax").
+;   - At the top level of a bench, t27c's gen_bench_block prints every `_ = e;` as written: the first through
+;     its W608 discard spelling, each later one through gen_stmt. Each is Zig's discard, whatever e's type, in
+;     an uncalled `fn bench_<name>() void` Zig never analyzes. specs/fpga/boards/arty_a7_integration.t27
+;     discards a u32, a u32, then a bool there (see #8195, #8546).
 ;   - specs/port/bootstrap/src/compiler/collect_type_decls.t27 writes `_ = process(node);` (a void fn) at the top
 ;     of a body, `_ = "literal";` in the arms of an `if`, and a trailing `_ = "literal";` that is deleted.
 ; --
 ; What t27b does. DELETED: at the top level of a fn body, an e with no call is not lowered at all, as the
 ; reference deletes it. EVALUATE: anywhere else, e is lowered and evaluated for its effects and its traps, and
 ; its value is dropped. NOT_MINE: a bare name (`_ = p;`, t27b's parameter-discard path, which models Zig's
-; pointless-discard rule), and any `_ = e;` at the top level of a test, invariant or bench (t27b's test-binding
-; path, left as it was).
+; pointless-discard rule), and any `_ = e;` at the top level of a test or invariant (t27b's test-binding path,
+; left as it was). At the top level of a bench that path bound `_` as a variable of the first e's type and
+; refused a later e of another type (`type mismatch`); there a discard is EVALUATE too, compiled, never run.
 ; ASCII only (L3)
 ; phi^2 + 1/phi^2 = 3 | TRINITY
 
@@ -35,11 +40,11 @@ pub const DELETED : u8 = 1;
 pub const EVALUATE : u8 = 2;
 
 /// The decision for one `_ = e;`. name: e is a bare name. test_top: the statement is at the top level of a test,
-/// invariant or bench. fn_top: it is at the top level of a fn body, where the reference's dead-store pass runs.
-/// call: e holds a call anywhere in it.
-pub fn plan(name: bool, test_top: bool, fn_top: bool, call: bool) -> u8 {
+/// invariant or bench. in_bench: it is in a bench body. fn_top: it is at the top level of a fn body, where the
+/// reference's dead-store pass runs. call: e holds a call anywhere in it.
+pub fn plan(name: bool, test_top: bool, in_bench: bool, fn_top: bool, call: bool) -> u8 {
     if (name) { return NOT_MINE; }
-    if (test_top) { return NOT_MINE; }
+    if (test_top and !in_bench) { return NOT_MINE; }
     if (fn_top and !call) { return DELETED; }
     return EVALUATE;
 }
@@ -55,28 +60,43 @@ pub fn runs(act: u8) -> bool {
 
 test a_call_discarded_at_the_top_of_a_fn_runs {
     // collect_type_decls.t27's `_ = process_node_for_types(node);`: kept by keep_call_discards.
-    assert(plan(false, false, true, true) == EVALUATE);
+    assert(plan(false, false, false, true, true) == EVALUATE);
     assert(runs(EVALUATE));
 }
 
 test a_discard_with_no_call_at_the_top_of_a_fn_is_deleted {
     // collect_type_decls.t27's trailing `_ = "children_processed";`, and `_ = a + b;`, which then cannot trap.
-    assert(plan(false, false, true, false) == DELETED);
+    assert(plan(false, false, false, true, false) == DELETED);
     assert(!runs(DELETED));
 }
 
 test a_nested_discard_runs_with_or_without_a_call {
     // collect_type_decls.t27's `_ = "struct_fields_collected";` in an arm of an `if`; a nested
     // `_ = a + b;` traps on overflow, as the reference's does.
-    assert(plan(false, false, false, false) == EVALUATE);
-    assert(plan(false, false, false, true) == EVALUATE);
+    assert(plan(false, false, false, false, false) == EVALUATE);
+    assert(plan(false, false, false, false, true) == EVALUATE);
 }
 
 test a_bare_name_and_a_test_binding_are_left_alone {
-    assert(plan(true, false, true, false) == NOT_MINE);
-    assert(plan(true, false, false, true) == NOT_MINE);
-    assert(plan(true, true, false, true) == NOT_MINE);
-    assert(plan(false, true, false, true) == NOT_MINE);
-    assert(plan(false, true, false, false) == NOT_MINE);
+    assert(plan(true, false, false, true, false) == NOT_MINE);
+    assert(plan(true, false, false, false, true) == NOT_MINE);
+    assert(plan(true, true, false, false, true) == NOT_MINE);
+    assert(plan(false, true, false, false, true) == NOT_MINE);
+    assert(plan(false, true, false, false, false) == NOT_MINE);
     assert(!runs(NOT_MINE));
 }
+
+test every_discard_at_the_top_of_a_bench_runs {
+    // arty_a7_integration.t27's bench_integration_config: `_ = calc_baud_divisor(..);` (a u32), then
+    // `_ = verify_pin_config(..);` (a bool), each its own discard.
+    assert(plan(false, true, true, false, true) == EVALUATE);
+    assert(plan(false, true, true, false, false) == EVALUATE);
+    assert(runs(plan(false, true, true, false, true)));
+}
+
+test a_nested_discard_in_a_bench_runs_and_a_bare_name_there_is_left_alone {
+    assert(plan(false, false, true, false, true) == EVALUATE);
+    assert(plan(false, false, true, false, false) == EVALUATE);
+    // ternary_gates.t27's `_ = result;` closing each bench.
+    assert(plan(true, true, true, false, false) == NOT_MINE);
+}