[Not a bug]Error evaluating expression. There may be a ..

[RobertL]

Code: Select all

;AHK V2 a-0.48+
_:=new()	;Error:  Error evaluating expression.  There may be a syntax error.

I though it means there is an error which dont sure why (may be a syntax error), if you find it, report it.
There's no result of search on 'Error evaluating expression. There may be a syntax error.', so made this one.
I know new is an reserved operator. Just my accidental error.
So, if useless, please ignore this.

[lexikos]

If it meant for you to report it, it would say "Please report it."

The error message is vague because it didn't detect a specific syntax error; it detected a runtime condition which is generally always indirectly caused by a syntax error.

[RobertL]

OK~Thanks.

[lexikos]

Also note that this condition isn't detected immediately, so strange things can happen, such as an unexpected value being used as input:

Code: Select all

try (x + C := new ())
MsgBox % IsObject(x)
class C {
	__New() {
		MsgBox C.__New
	}
}

This is because expressions are "pre-compiled" to postfix form, like:

Code: Select all

push x
push C
; ... missing push class_object_for_new ...
call new, 1 input   ; consumes C as input (unintended)
assign   ; intended input: C, (result of new); actual input: x, (result of new)
add   ; intended input: x, C; actual input: C, <insufficient inputs>

[RobertL]

I see, operand (bottom to top) x-c-missing_class_object_for_new, then operator new, pop top operandc..
If change all operator to function, then easy to take which is uniformity but not convenient.
Thanks to point out.

BTW, I didn't reappear any error with your demo in AHK V1.1.16, just show '0' by first Msgbox, with or without try.

[lexikos]

The error didn't "reappear", but it was there. The difference is that in v1, new is only treated as an operator if followed by a variable name. So it's like this case (you can replace _new_ with new in v1):

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C := 4
_new_ := 2
try (x + C := _new_ ())
MsgBox % x=42

[RobertL]

Haha, interesting, but didnt find a way to use this 'feature',..joking.

一些中文/Chinese记录：new运算符