Improve type checker

Author: antonmedv

checker/checker.go

@@ -275,14 +275,22 @@ func (v *visitor) BinaryNode(node *ast.BinaryNode) (reflect.Type, info) {
 			return anyType, info{}
 		}
 
-	case "/", "*":
+	case "*":
 		if isNumber(l) && isNumber(r) {
 			return combined(l, r), info{}
 		}
 		if or(l, r, isNumber) {
 			return anyType, info{}
 		}
 
+	case "/":
+		if isNumber(l) && isNumber(r) {
+			return floatType, info{}
+		}
+		if or(l, r, isNumber) {
+			return floatType, info{}
+		}
+
 	case "**", "^":
 		if isNumber(l) && isNumber(r) {
 			return floatType, info{}
@@ -321,15 +329,21 @@ func (v *visitor) BinaryNode(node *ast.BinaryNode) (reflect.Type, info) {
 			return boolType, info{}
 		}
 		if isMap(r) {
-			if l == nil {
-				return v.error(node, "cannot use nil as map key")
+			if l == nil { // It is possible to compare with nil.
+				return boolType, info{}
 			}
 			if !isAny(l) && !l.AssignableTo(r.Key()) {
-				return v.error(node, "cannot use %v (type %v) as type %v in map key", l, l, r.Key())
+				return v.error(node, "cannot use %v as type %v in map key", l, r.Key())
 			}
 			return boolType, info{}
 		}
-		if isInteger(l) && isArray(r) {
+		if isArray(r) {
+			if l == nil { // It is possible to compare with nil.
+				return boolType, info{}
+			}
+			if !isAny(l) && !isInteger(l) {
+				return v.error(node, "cannot use %v as type %v in array", l, r.Elem())
+			}
 			return boolType, info{}
 		}
 		if isAny(l) && anyOf(r, isString, isArray, isMap) {

checker/checker_test.go

@@ -55,13 +55,13 @@ var successTests = []string{
 	"(Any ? 0 : nil) == 0",
 	"(Any ? nil : nil) == nil",
 	"!(Any ? Foo : Foo.Bar).Anything",
-	"String in ArrayOfFoo",
+	"Int in ArrayOfFoo",
+	"Int not in ArrayOfFoo",
 	"String in Foo",
 	"String in MapOfFoo",
 	"String matches 'ok'",
 	"String matches Any",
 	"String not matches Any",
-	"String not in ArrayOfFoo",
 	"StringPtr == nil",
 	"[1, 2, 3] == []",
 	"len([]) > 0",
@@ -491,9 +491,14 @@ cannot use int as argument (type string) to call FuncTyped  (1:11)
  | ..........^
 
 .0 in MapOfFoo
-cannot use float64 (type float64) as type string in map key (1:4)
+cannot use float64 as type string in map key (1:4)
  | .0 in MapOfFoo
  | ...^
+
+1/2 in MapIntAny
+cannot use float64 as type int in map key (1:5)
+ | 1/2 in MapIntAny
+ | ....^
 `
 
 func TestCheck_error(t *testing.T) {