diff --git a/internal/shader/expr.go b/internal/shader/expr.go
index 31774f9cb..93c2408f3 100644
--- a/internal/shader/expr.go
+++ b/internal/shader/expr.go
@@ -346,7 +346,15 @@ func (cs *compileState) parseExpr(block *block, expr ast.Expr, markLocalVariable
 					},
 				}, []shaderir.Type{{Main: shaderir.Int}}, stmts, true
 			case shaderir.IntF:
-				if args[0].Type == shaderir.NumberExpr && canTruncateToInteger(args[0].Const) {
+				if len(args) != 1 {
+					cs.addError(e.Pos(), fmt.Sprintf("number of %s's arguments must be 1 but %d", callee.BuiltinFunc, len(args)))
+					return nil, nil, nil, false
+				}
+				if args[0].Type == shaderir.NumberExpr {
+					if !canTruncateToInteger(args[0].Const) {
+						cs.addError(e.Pos(), fmt.Sprintf("cannot convert %s to type int", args[0].Const.String()))
+						return nil, nil, nil, false
+					}
 					return []shaderir.Expr{
 						{
 							Type:      shaderir.NumberExpr,
@@ -356,14 +364,20 @@ func (cs *compileState) parseExpr(block *block, expr ast.Expr, markLocalVariable
 					}, []shaderir.Type{{Main: shaderir.Int}}, stmts, true
 				}
 			case shaderir.FloatF:
+				if len(args) != 1 {
+					cs.addError(e.Pos(), fmt.Sprintf("number of %s's arguments must be 1 but %d", callee.BuiltinFunc, len(args)))
+					return nil, nil, nil, false
+				}
 				if args[0].Type == shaderir.NumberExpr {
-					return []shaderir.Expr{
-						{
-							Type:      shaderir.NumberExpr,
-							Const:     gconstant.ToFloat(args[0].Const),
-							ConstType: shaderir.ConstTypeFloat,
-						},
-					}, []shaderir.Type{{Main: shaderir.Float}}, stmts, true
+					if args[0].Const.Kind() == gconstant.Int || args[0].Const.Kind() == gconstant.Float {
+						return []shaderir.Expr{
+							{
+								Type:      shaderir.NumberExpr,
+								Const:     gconstant.ToFloat(args[0].Const),
+								ConstType: shaderir.ConstTypeFloat,
+							},
+						}, []shaderir.Type{{Main: shaderir.Float}}, stmts, true
+					}
 				}
 			case shaderir.Atan:
 				if len(args) != 1 {
@@ -379,13 +393,22 @@ func (cs *compileState) parseExpr(block *block, expr ast.Expr, markLocalVariable
 			var t shaderir.Type
 			switch callee.BuiltinFunc {
 			case shaderir.BoolF:
-				// TODO: Check arg types.
+				if err := checkArgsForBoolBuiltinFunc(args, argts); err != nil {
+					cs.addError(e.Pos(), err.Error())
+					return nil, nil, nil, false
+				}
 				t = shaderir.Type{Main: shaderir.Bool}
 			case shaderir.IntF:
-				// TODO: Check arg types.
+				if err := checkArgsForIntBuiltinFunc(args, argts); err != nil {
+					cs.addError(e.Pos(), err.Error())
+					return nil, nil, nil, false
+				}
 				t = shaderir.Type{Main: shaderir.Int}
 			case shaderir.FloatF:
-				// TODO: Check arg types.
+				if err := checkArgsForFloatBuiltinFunc(args, argts); err != nil {
+					cs.addError(e.Pos(), err.Error())
+					return nil, nil, nil, false
+				}
 				t = shaderir.Type{Main: shaderir.Float}
 			case shaderir.Vec2F:
 				if err := checkArgsForVec2BuiltinFunc(args, argts); err != nil {
diff --git a/internal/shader/syntax_test.go b/internal/shader/syntax_test.go
index 42037ab6d..a8741bbec 100644
--- a/internal/shader/syntax_test.go
+++ b/internal/shader/syntax_test.go
@@ -1358,6 +1358,33 @@ func TestSyntaxBuiltinFuncType(t *testing.T) {
 		stmt string
 		err  bool
 	}{
+		{stmt: "a := bool(false); _ = a", err: false},
+		{stmt: "i := false; a := bool(i); _ = a", err: false},
+		{stmt: "a := bool(1); _ = a", err: true},
+		{stmt: "a := bool(1.0); _ = a", err: true},
+		{stmt: "a := bool(); _ = a", err: true},
+		{stmt: "a := bool(false, true); _ = a", err: true},
+
+		{stmt: "a := int(1); _ = a", err: false},
+		{stmt: "a := int(1.0); _ = a", err: false},
+		{stmt: "i := 1; a := int(i); _ = a", err: false},
+		{stmt: "i := 1.0; a := int(i); _ = a", err: false},
+		{stmt: "i := 1.1; a := int(i); _ = a", err: false},
+		{stmt: "a := int(1.1); _ = a", err: true},
+		{stmt: "a := int(false); _ = a", err: true},
+		{stmt: "a := int(); _ = a", err: true},
+		{stmt: "a := int(1, 2); _ = a", err: true},
+
+		{stmt: "a := float(1); _ = a", err: false},
+		{stmt: "a := float(1.0); _ = a", err: false},
+		{stmt: "a := float(1.1); _ = a", err: false},
+		{stmt: "i := 1; a := float(i); _ = a", err: false},
+		{stmt: "i := 1.0; a := float(i); _ = a", err: false},
+		{stmt: "i := 1.1; a := float(i); _ = a", err: false},
+		{stmt: "a := float(false); _ = a", err: true},
+		{stmt: "a := float(); _ = a", err: true},
+		{stmt: "a := float(1, 2); _ = a", err: true},
+
 		{stmt: "a := vec2(1); _ = a", err: false},
 		{stmt: "a := vec2(1.0); _ = a", err: false},
 		{stmt: "i := 1; a := vec2(i); _ = a", err: false},
diff --git a/internal/shader/type.go b/internal/shader/type.go
index 28ac89c71..e32a61237 100644
--- a/internal/shader/type.go
+++ b/internal/shader/type.go
@@ -119,6 +119,54 @@ func canBeFloatImplicitly(expr shaderir.Expr, t shaderir.Type) bool {
 	return false
 }
 
+func checkArgsForBoolBuiltinFunc(args []shaderir.Expr, argts []shaderir.Type) error {
+	if len(args) != len(argts) {
+		return fmt.Errorf("the number of arguments and types doesn't match: %d vs %d", len(args), len(argts))
+	}
+
+	if len(args) != 1 {
+		return fmt.Errorf("number of bool's arguments must be 1 but %d", len(args))
+	}
+	if argts[0].Main == shaderir.Bool {
+		return nil
+	}
+	if args[0].Const != nil && args[0].Const.Kind() == gconstant.Bool {
+		return nil
+	}
+	return fmt.Errorf("invalid arguments for bool: (%s)", argts[0].String())
+}
+
+func checkArgsForIntBuiltinFunc(args []shaderir.Expr, argts []shaderir.Type) error {
+	if len(args) != len(argts) {
+		return fmt.Errorf("the number of arguments and types doesn't match: %d vs %d", len(args), len(argts))
+	}
+
+	if len(args) != 1 {
+		return fmt.Errorf("number of int's arguments must be 1 but %d", len(args))
+	}
+	if argts[0].Main == shaderir.Int || argts[0].Main == shaderir.Float {
+		return nil
+	}
+	if args[0].Const != nil && canTruncateToInteger(args[0].Const) {
+		return nil
+	}
+	return fmt.Errorf("invalid arguments for int: (%s)", argts[0].String())
+}
+
+func checkArgsForFloatBuiltinFunc(args []shaderir.Expr, argts []shaderir.Type) error {
+	if len(args) != len(argts) {
+		return fmt.Errorf("the number of arguments and types doesn't match: %d vs %d", len(args), len(argts))
+	}
+
+	if len(args) != 1 {
+		return fmt.Errorf("number of float's arguments must be 1 but %d", len(args))
+	}
+	if canBeFloatImplicitly(args[0], argts[0]) {
+		return nil
+	}
+	return fmt.Errorf("invalid arguments for float: (%s)", argts[0].String())
+}
+
 func checkArgsForVec2BuiltinFunc(args []shaderir.Expr, argts []shaderir.Type) error {
 	if len(args) != len(argts) {
 		return fmt.Errorf("the number of arguments and types doesn't match: %d vs %d", len(args), len(argts))
@@ -137,7 +185,7 @@ func checkArgsForVec2BuiltinFunc(args []shaderir.Expr, argts []shaderir.Type) er
 			return nil
 		}
 	default:
-		return fmt.Errorf("too many arguments for vec2")
+		return fmt.Errorf("invalid number of arguments for vec2")
 	}
 
 	var str []string
@@ -172,7 +220,7 @@ func checkArgsForVec3BuiltinFunc(args []shaderir.Expr, argts []shaderir.Type) er
 			return nil
 		}
 	default:
-		return fmt.Errorf("too many arguments for vec3")
+		return fmt.Errorf("invalid number of arguments for vec3")
 	}
 
 	var str []string
@@ -220,7 +268,7 @@ func checkArgsForVec4BuiltinFunc(args []shaderir.Expr, argts []shaderir.Type) er
 			return nil
 		}
 	default:
-		return fmt.Errorf("too many arguments for vec4")
+		return fmt.Errorf("invalid number of arguments for vec4")
 	}
 
 	var str []string