Add better nil checks

Author: antonmedv

expr_test.go

@@ -436,6 +436,7 @@ func TestExpr(t *testing.T) {
 			return ret
 		},
 		Inc: func(a int) int { return a + 1 },
+		Nil: nil,
 	}
 
 	tests := []struct {
@@ -731,13 +732,17 @@ func TestExpr(t *testing.T) {
 			"bar",
 		},
 		{
-			`Nil`,
+			`NilStruct`,
 			(*time.Time)(nil),
 		},
 		{
-			`Nil == nil && nil == Nil && nil == nil && Nil == Nil`,
+			`Nil == nil && nil == Nil && nil == nil && Nil == Nil && NilInt == nil && NilSlice == nil && NilStruct == nil`,
 			true,
 		},
+		{
+			`0 == nil || "str" == nil || true == nil`,
+			false,
+		},
 	}
 
 	for _, tt := range tests {
@@ -786,7 +791,10 @@ type mockEnv struct {
 	Segments             []*segment
 	BirthDay             time.Time
 	Now                  time.Time
-	Nil                  *time.Time
+	Nil                  interface{}
+	NilStruct            *time.Time
+	NilInt               *int
+	NilSlice             []ticket
 }
 
 func (e *mockEnv) GetInt() int {

vm/generate/main.go

@@ -123,12 +123,13 @@ func main() {
 		}
 		if helper.string {
 			echo(`case string:`)
-			echo(`return x %v b.(string)`, op)
+			echo(`switch y := b.(type) {`)
+			echo(`case string: return x %v y`, op)
+			echo(`}`)
 		}
 		echo(`}`)
 		if name == "equal" {
-			echo(`// Two nil values should be considered as equal.`)
-			echo(`if (a == nil || reflect.ValueOf(a).IsNil()) && (b == nil || reflect.ValueOf(b).IsNil()) { return true }`)
+			echo(`if isNil(a) && isNil(b) { return true }`)
 			echo(`return reflect.DeepEqual(a, b)`)
 		} else {
 			echo(`panic(fmt.Sprintf("invalid operation: %%T %%v %%T", a, "%v", b))`, op)

vm/helpers.go

@@ -332,10 +332,12 @@ func equal(a, b interface{}) interface{} {
 			return x == y
 		}
 	case string:
-		return x == b.(string)
+		switch y := b.(type) {
+		case string:
+			return x == y
+		}
 	}
-	// Two nil values should be considered as equal.
-	if (a == nil || reflect.ValueOf(a).IsNil()) && (b == nil || reflect.ValueOf(b).IsNil()) {
+	if isNil(a) && isNil(b) {
 		return true
 	}
 	return reflect.DeepEqual(a, b)
@@ -668,7 +670,10 @@ func less(a, b interface{}) interface{} {
 			return x < y
 		}
 	case string:
-		return x < b.(string)
+		switch y := b.(type) {
+		case string:
+			return x < y
+		}
 	}
 	panic(fmt.Sprintf("invalid operation: %T %v %T", a, "<", b))
 }
@@ -1000,7 +1005,10 @@ func more(a, b interface{}) interface{} {
 			return x > y
 		}
 	case string:
-		return x > b.(string)
+		switch y := b.(type) {
+		case string:
+			return x > y
+		}
 	}
 	panic(fmt.Sprintf("invalid operation: %T %v %T", a, ">", b))
 }
@@ -1332,7 +1340,10 @@ func lessOrEqual(a, b interface{}) interface{} {
 			return x <= y
 		}
 	case string:
-		return x <= b.(string)
+		switch y := b.(type) {
+		case string:
+			return x <= y
+		}
 	}
 	panic(fmt.Sprintf("invalid operation: %T %v %T", a, "<=", b))
 }
@@ -1664,7 +1675,10 @@ func moreOrEqual(a, b interface{}) interface{} {
 			return x >= y
 		}
 	case string:
-		return x >= b.(string)
+		switch y := b.(type) {
+		case string:
+			return x >= y
+		}
 	}
 	panic(fmt.Sprintf("invalid operation: %T %v %T", a, ">=", b))
 }
@@ -1996,7 +2010,10 @@ func add(a, b interface{}) interface{} {
 			return x + y
 		}
 	case string:
-		return x + b.(string)
+		switch y := b.(type) {
+		case string:
+			return x + y
+		}
 	}
 	panic(fmt.Sprintf("invalid operation: %T %v %T", a, "+", b))
 }

vm/runtime.go

@@ -313,3 +313,16 @@ func toFloat64(a interface{}) float64 {
 		panic(fmt.Sprintf("invalid operation: float64(%T)", x))
 	}
 }
+
+func isNil(v interface{}) bool {
+	if v == nil {
+		return true
+	}
+	r := reflect.ValueOf(v)
+	switch r.Kind() {
+	case reflect.Chan, reflect.Func, reflect.Map, reflect.Ptr, reflect.Interface, reflect.Slice:
+		return r.IsNil()
+	default:
+		return false
+	}
+}