Fix type checker for "in" operator

Fixes #426

checker/checker.go

@@ -242,16 +242,7 @@ func (v *checker) BinaryNode(node *ast.BinaryNode) (reflect.Type, info) {
 
 	switch node.Operator {
 	case "==", "!=":
-		if isNumber(l) && isNumber(r) {
-			return boolType, info{}
-		}
-		if l == nil || r == nil { // It is possible to compare with nil.
-			return boolType, info{}
-		}
-		if l.Kind() == r.Kind() {
-			return boolType, info{}
-		}
-		if isAny(l) || isAny(r) {
+		if isComparable(l, r) {
 			return boolType, info{}
 		}
 
@@ -357,7 +348,7 @@ func (v *checker) BinaryNode(node *ast.BinaryNode) (reflect.Type, info) {
 			if l == nil { // It is possible to compare with nil.
 				return boolType, info{}
 			}
-			if !isAny(l) && !l.AssignableTo(r.Elem()) && !(isInteger(l) && isInteger(r.Elem())) {
+			if !isComparable(l, r.Elem()) {
 				return v.error(node, "cannot use %v as type %v in array", l, r.Elem())
 			}
 			return boolType, info{}

checker/checker_test.go

@@ -513,6 +513,11 @@ cannot use float64 as type int in map key (1:5)
  | 1/2 in MapIntAny
  | ....^
 
+0.5 in ArrayOfFoo
+cannot use float64 as type *mock.Foo in array (1:5)
+ | 0.5 in ArrayOfFoo
+ | ....^
+
 repeat("0", 1/0)
 cannot use float64 as argument (type int) to call repeat  (1:14)
  | repeat("0", 1/0)

checker/types.go

@@ -227,3 +227,18 @@ func kind(t reflect.Type) reflect.Kind {
 	}
 	return t.Kind()
 }
+
+func isComparable(l, r reflect.Type) bool {
+	if l == nil || r == nil {
+		return true
+	}
+	switch {
+	case l.Kind() == r.Kind():
+		return true
+	case isNumber(l) && isNumber(r):
+		return true
+	case isAny(l) || isAny(r):
+		return true
+	}
+	return false
+}

expr_test.go

@@ -1084,6 +1084,14 @@ func TestExpr(t *testing.T) {
 			`4/2 == 2`,
 			true,
 		},
+		{
+			`.5 in 0..1`,
+			false,
+		},
+		{
+			`.5 in ArrayOfInt`,
+			false,
+		},
 	}
 
 	for _, tt := range tests {