internal/shader: add type checks for the builtin function clamp

Updates #2184

internal/shader/expr.go

@@ -453,6 +453,31 @@ func (cs *compileState) parseExpr(block *block, fname string, expr ast.Expr, mar
 				})
 				return nil, nil, stmts, true
 
+			case shaderir.Clamp:
+				// 3 arguments
+				if len(args) != 3 {
+					cs.addError(e.Pos(), fmt.Sprintf("number of %s's arguments must be 3 but %d", callee.BuiltinFunc, len(args)))
+					return nil, nil, nil, false
+				}
+				for i := range args {
+					// If the argument is a non-typed constant value, treat this as a float value (#1874).
+					if args[i].Type == shaderir.NumberExpr && args[i].ConstType == shaderir.ConstTypeNone && gconstant.ToFloat(args[i].Const).Kind() != gconstant.Unknown {
+						args[i].Const = gconstant.ToFloat(args[i].Const)
+						args[i].ConstType = shaderir.ConstTypeFloat
+						argts[i] = shaderir.Type{Main: shaderir.Float}
+					}
+					if argts[i].Main != shaderir.Float && argts[i].Main != shaderir.Vec2 && argts[i].Main != shaderir.Vec3 && argts[i].Main != shaderir.Vec4 {
+						cs.addError(e.Pos(), fmt.Sprintf("cannot use %s as float, vec2, vec3, or vec4 value in argument to %s", argts[i].String(), callee.BuiltinFunc))
+						return nil, nil, nil, false
+					}
+				}
+				if (!argts[0].Equal(&argts[1]) || !argts[0].Equal(&argts[2])) && (argts[1].Main != shaderir.Float || argts[2].Main != shaderir.Float) {
+					cs.addError(e.Pos(), fmt.Sprintf("the second and the third arguments for %s must equal to the first argument %s or float but %s and %s", callee.BuiltinFunc, argts[0].String(), argts[1].String(), argts[2].String()))
+					return nil, nil, nil, false
+				}
+
+				t = argts[0]
+
 			case shaderir.Atan2, shaderir.Mod, shaderir.Min, shaderir.Max, shaderir.Distance, shaderir.Dot, shaderir.Cross, shaderir.Reflect:
 				// 2 arguments
 				if len(args) != 2 {

internal/shader/syntax_test.go

@@ -1793,6 +1793,56 @@ func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
 	}
 }
 
+// Issue #2184
+func TestSyntaxBuiltinFuncClampType(t *testing.T) {
+	cases := []struct {
+		stmt string
+		err  bool
+	}{
+		{stmt: "a := clamp(); _ = a", err: true},
+		{stmt: "a := clamp(1); _ = a", err: true},
+		{stmt: "a := clamp(false, false); _ = a", err: true},
+		{stmt: "a := clamp(1, 1); _ = a", err: true},
+		{stmt: "a := clamp(false, false, false); _ = a", err: true},
+		{stmt: "a := clamp(1, 1, 1); _ = a", err: false},
+		{stmt: "a := clamp(1.0, 1, 1); _ = a", err: false},
+		{stmt: "a := clamp(1, 1.0, 1); _ = a", err: false},
+		{stmt: "a := clamp(1, 1, 1.0); _ = a", err: false},
+		{stmt: "a := clamp(1, vec2(1), 1); _ = a", err: true},
+		{stmt: "a := clamp(1, 1, vec2(1)); _ = a", err: true},
+		{stmt: "a := clamp(1, vec2(1), vec2(1)); _ = a", err: true},
+		{stmt: "a := clamp(vec2(1), 1, 1); _ = a", err: false},
+		{stmt: "a := clamp(vec2(1), 1, vec2(1)); _ = a", err: true},
+		{stmt: "a := clamp(vec2(1), vec2(1), 1); _ = a", err: true},
+		{stmt: "a := clamp(vec2(1), vec2(1), vec2(1)); _ = a", err: false},
+		{stmt: "a := clamp(vec2(1), vec2(1), vec3(1)); _ = a", err: true},
+		{stmt: "a := clamp(vec3(1), 1, 1); _ = a", err: false},
+		{stmt: "a := clamp(vec3(1), 1, vec3(1)); _ = a", err: true},
+		{stmt: "a := clamp(vec3(1), vec3(1), 1); _ = a", err: true},
+		{stmt: "a := clamp(vec3(1), vec3(1), vec3(1)); _ = a", err: false},
+		{stmt: "a := clamp(vec4(1), 1, 1); _ = a", err: false},
+		{stmt: "a := clamp(vec4(1), 1, vec4(1)); _ = a", err: true},
+		{stmt: "a := clamp(vec4(1), vec4(1), 1); _ = a", err: true},
+		{stmt: "a := clamp(vec4(1), vec4(1), vec4(1)); _ = a", err: false},
+	}
+
+	for _, c := range cases {
+		stmt := c.stmt
+		src := fmt.Sprintf(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	%s
+	return position
+}`, stmt)
+		_, err := compileToIR([]byte(src))
+		if err == nil && c.err {
+			t.Errorf("%s must return an error but does not", stmt)
+		} else if err != nil && !c.err {
+			t.Errorf("%s must not return nil but returned %v", stmt, err)
+		}
+	}
+}
+
 // Issue #2184
 func TestSyntaxBuiltinFuncCrossType(t *testing.T) {
 	cases := []struct {