fix for in loop symbols (#290)

* fix for in loop symbols

* fix comments

compiler.go

@@ -847,8 +847,8 @@ func (c *Compiler) compileForInStmt(stmt *parser.ForInStmt) error {
 	//     ... body ...
 	//   }
 	//
-	// ":it" is a local variable but will be conflict with other user variables
-	// because character ":" is not allowed.
+	// ":it" is a local variable but it will not conflict with other user variables
+	// because character ":" is not allowed in the variable names.
 
 	// init
 	//   :it = iterator(iterable)
@@ -893,6 +893,7 @@ func (c *Compiler) compileForInStmt(stmt *parser.ForInStmt) error {
 		if keySymbol.Scope == ScopeGlobal {
 			c.emit(stmt, parser.OpSetGlobal, keySymbol.Index)
 		} else {
+			keySymbol.LocalAssigned = true
 			c.emit(stmt, parser.OpDefineLocal, keySymbol.Index)
 		}
 	}
@@ -909,6 +910,7 @@ func (c *Compiler) compileForInStmt(stmt *parser.ForInStmt) error {
 		if valueSymbol.Scope == ScopeGlobal {
 			c.emit(stmt, parser.OpSetGlobal, valueSymbol.Index)
 		} else {
+			valueSymbol.LocalAssigned = true
 			c.emit(stmt, parser.OpDefineLocal, valueSymbol.Index)
 		}
 	}

vm_test.go

@@ -1531,7 +1531,23 @@ func TestFunction(t *testing.T) {
 		add2 := newAdder(2);
 		out = add2(5);
 		`, nil, 7)
+	expectRun(t, `
+		m := {a: 1}
+		for k,v in m {
+			func(){
+				out = k
+			}()
+		}
+		`, nil, "a")
 
+	expectRun(t, `
+		m := {a: 1}
+		for k,v in m {
+			func(){
+				out = v
+			}()
+		}
+		`, nil, 1)
 	// function as a argument
 	expectRun(t, `
 	add := func(a, b) { return a + b };