internal/shader: bug fix: untyped const bool couldn't be an if condition

Closes #2993

internal/shader/stmt.go

@@ -251,7 +251,7 @@ func (cs *compileState) parseStmt(block *block, fname string, stmt ast.Stmt, inP
 		if !ok {
 			return nil, false
 		}
-		if len(ts) != 1 || ts[0].Main != shaderir.Bool {
+		if len(ts) != 1 {
 			var tss []string
 			for _, t := range ts {
 				tss = append(tss, t.String())
@@ -259,6 +259,10 @@ func (cs *compileState) parseStmt(block *block, fname string, stmt ast.Stmt, inP
 			cs.addError(stmt.Pos(), fmt.Sprintf("if-condition must be bool but: %s", strings.Join(tss, ", ")))
 			return nil, false
 		}
+		if !(ts[0].Main == shaderir.Bool || (ts[0].Main == shaderir.None && exprs[0].Const != nil && exprs[0].Const.Kind() == gconstant.Bool)) {
+			cs.addError(stmt.Pos(), fmt.Sprintf("if-condition must be bool but: %s", ts[0].String()))
+			return nil, false
+		}
 		stmts = append(stmts, ss...)
 
 		var bs []*shaderir.Block

internal/shader/syntax_test.go

@@ -4335,3 +4335,31 @@ func Bar() float {
 		t.Error("compileToIR must return an error but did not")
 	}
 }
+
+// Issue #2993
+func TestSyntaxIfAndConstBool(t *testing.T) {
+	if _, err := compileToIR([]byte(`package main
+
+func Foo() int {
+	const X = true
+	if X {
+		return 1
+	}
+	return 0
+}
+`)); err != nil {
+		t.Error(err)
+	}
+	if _, err := compileToIR([]byte(`package main
+
+func Foo() int {
+	const X bool = true
+	if X {
+		return 1
+	}
+	return 0
+}
+`)); err != nil {
+		t.Error(err)
+	}
+}