Awkward error using first-class callable syntax with missing function

[othercorey]

Description

The following code:

<?php

'missing'(...);

Resulted in this output:

Fatal error: Uncaught Error: Call to undefined function missing() 

But I expected this output instead:

Fatal error: Uncaught Error: Unable to create closure from undefined function missing() 

When using the first-class callable syntax on a missing function, the error message claims the user is calling a function. However, this should only be creating a closure.

I thought the (...) syntax would only try to create a closure. Does it actually try to call the function with a ... argument if it's not found?

If you use the original Closure::fromCallable() method, the error is different.

Closure::fromCallable('missing');

Uncaught TypeError: Failed to create closure from callable: function "missing" not found or invalid function name

PHP Version

8.1

Operating System

No response

[cmb69]

The problem is that the callable syntax causes an INIT_* opcode to be emitted, and afterwards an CALLABLE_CONVERT to convert to the call frame to closure. However, if the function is not defined, the INIT_* fails, causing the error message.

Having a proper error message has been discussed, but is not generally possible. Maybe we should just document this issue more clearly?

[othercorey]

Maybe we should just document this issue more clearly?

Documentation of the expected error would greatly improve this.

[cmb69]

I keep this ticket here for a while; maybe someone comes up with a way to improve the error message.

[nikic]

Any thoughts on the suggestion to use more generic error messages (that don't use "call" terminology) from #7019 (comment)?

[cmb69]

@nikic, like you already said there: "Though maybe that makes the message in the common case slightly harder to understand." Particularly, the word "reference" might cause some confusion regarding references (&). OTOH, the wording is actually more precise even for the call-case.

[othercorey]

Particularly, the word "reference" might cause some confusion regarding references (&). OTOH, the wording is actually more precise even for the call-case.

If I may offer an opinion, even though it's throwing an error, prefixing with "Unable to", might help.

From:

Reference to private method Foo::bar() from Baz

To:

Unable to reference to private method Foo::bar() from Baz

If the code that's throwing the error is always just resolving functions, then you could say Locating instead of Reference. If locating the function fails then naturally any use of it would fail after.

[othercorey]

@nikic I don't suppose there's a chance of making this error more generic for 8.2?