Enable checking guards are boolean

This adds support for checking that guards have boolean semantics.  For
now, checking constraints have loobean semantics is implemented but not
enabled.  The problem is that it breaks a lot of the existing tests!

pkg/corset/resolver.go

@@ -297,15 +297,27 @@ func (r *resolver) finaliseDefConstInModule(enclosing Scope, decl *DefConst) []S
 func (r *resolver) finaliseDefConstraintInModule(enclosing Scope, decl *DefConstraint) []SyntaxError {
 	var (
 		guard_errors []SyntaxError
+		guard_t      Type
 		scope        = NewLocalScope(enclosing, false, false)
 	)
 	// Resolve guard
 	if decl.Guard != nil {
-		// FIXME: check for boolean semantics!
-		_, guard_errors = r.finaliseExpressionInModule(scope, decl.Guard)
+		guard_t, guard_errors = r.finaliseExpressionInModule(scope, decl.Guard)
+		//
+		if guard_t != nil && !guard_t.HasBooleanSemantics() {
+			msg := fmt.Sprintf("expected boolean guard (found %s)", guard_t.String())
+			err := r.srcmap.SyntaxError(decl.Guard, msg)
+			guard_errors = append(guard_errors, *err)
+		}
 	}
 	// Resolve constraint body
 	_, errors := r.finaliseExpressionInModule(scope, decl.Constraint)
+	//
+	// if constraint_t != nil && !constraint_t.HasLoobeanSemantics() {
+	//	msg := fmt.Sprintf("expected loobean constraint (found %s)", constraint_t.String())
+	//	err := r.srcmap.SyntaxError(decl.Constraint, msg)
+	//	errors = append(errors, *err)
+	// }
 	// Done
 	return append(guard_errors, errors...)
 }

testdata/basic_01.lisp

@@ -1,2 +1,2 @@
-(defcolumns X)
+(defcolumns (X :byte@loob))
 (defconstraint heartbeat () X)

testdata/type_06.accepts

@@ -30,5 +30,5 @@
 { "BIT": [0,2], "X": [1,0] }
 { "BIT": [0,2], "X": [2,0] }
 ;;
-{ "BIT": [1,1], "X": [1,1] }
-{ "BIT": [2,2], "X": [1,1] }
+{ "BIT": [1,1], "X": [0,0] }
+{ "BIT": [2,2], "X": [0,0] }

testdata/type_08.accepts

@@ -24,4 +24,4 @@
 { "BIT": [0,1], "X": [1,0] }
 { "BIT": [0,1], "X": [2,0] }
 ;;
-{ "BIT": [1,1], "X": [1,1] }
+{ "BIT": [1,1], "X": [0,0] }