wcc/ww: reject non-constant array dimension (tinfofornode N_TARRAY)

arrayelen silently folded a non-const dimension to 0 — the 0-sized
slot aliased its neighbor (review item: cs loud / ww rc=0 clobber).
Mirror cstage check.c:715. Test rows land with the wave's final commit.

selfhost/cmd/wwdump/main.combined.ww

@@ -12434,7 +12434,32 @@ fn tinfofornode(c: *checker, n: *node) *tinfo = {
 		// Reverts A.4's r.size override (which conflated stride with
 		// natural size); the slot-padded stride now lives in slotsize
 		// where cgenutil's fast-path reads it.
-		let elen: u64 = arrayelen(c, n.rhs);	// #141: fold def-dim
+		// #38/F2 (review item 2): a non-const, non-`[_]T` dimension is
+		// LOUD here, mirroring cstage resolve_type N_TARRAY
+		// (cmd/wcc/check.c:715 "array length must be an integer literal").
+		// arrayelen folds 0 for both the `[_]T` sentinel AND a runtime
+		// dim, so the size-walker reader (astsize, via arrayelen) can't
+		// tell them apart; resolve the type HERE — the one resolve seam
+		// cstage gates at — so c.errs trips before any 0-sized slot ships.
+		// The fold is inlined (not via arrayelen) to error exactly once:
+		// evaldefconst itself reports div-by-zero / unsupported-op, so a
+		// guard that re-folds would double-report. arrayelen stays the
+		// fold SSoT for astsize's later size() read.
+		let elen: u64 = 0u64;	// #141: fold def-dim
+		if (n.rhs != nil) {
+			if (n.rhs.kind == nkind.N_INTLIT) {
+				elen = n.rhs.uval;
+			} else {
+				let v: u64 = 0u64;
+				if (evaldefconst(c, n.rhs, &v, 0)) {
+					elen = v;
+				} else {
+					cerr(n.file); cerr(": ");
+					cerr("error: array length must be an integer literal\n");
+					c.errs += 1;
+				};
+			};
+		};
 		let sub: *tinfo = tinfofornode(c, n.lhs);
 		// #62/#69: `type a = [2]a` value cycle — loud, cstage twin.
 		if (circularnamed(c, sub, n)) { sub = c.tc.tyerr; };