Answer architecture round 2: refuse by default where a builtin's operand can be a reference, test the flag against each operand grammar, drop a duplicate test, rename allNeverNumeric, rewrap Computation, and order item 91 after item 4

builtins_test.go

@@ -4,6 +4,7 @@ import (
 	"encoding/base64"
 	"fmt"
 	"regexp"
+	"slices"
 	"strconv"
 	"strings"
 	"testing"
@@ -447,3 +448,14 @@ func TestArgErrorsNameTheSpelling(t *testing.T) {
 		}
 	}
 }
+
+func TestNoRefOperandsMatchesTheOperandGrammar(t *testing.T) {
+	for name, b := range builtins {
+		if b.operands == nil {
+			continue
+		}
+		if takesRef := slices.ContainsFunc(b.operands([]string{"/x"}), isRef); b.noRefOperands == takesRef {
+			t.Errorf("%s: noRefOperands = %v, but its operands func reads a reference: %v", name, b.noRefOperands, takesRef)
+		}
+	}
+}