Passing anonymous proc params to templates may fail - Githubissues

nim-lang / Nim

Nim is a statically typed compiled systems programming language. It combines successful concepts from mature languages like Python, Ada and Modula. Its design focuses on efficiency, expressiveness, and elegance (in that order of priority).

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Passing anonymous proc params to templates may fail #18648

Open etan-k opened 3 years ago

etan-k commented 3 years ago

Passing an anonymous proc to a template may fail under Nim 1.2.12.

Example

type
  X* = ref object
    bar: proc (p: proc(v: openArray[byte]))

template foo(x: X, p: proc(v: openArray[byte])) =
  x.bar(p)

X().foo(proc(v: openArray[byte]) = discard @v)

Current Output

Error: internal error: expr: param not init v_4602025

Expected Output

Compilation should succeed

Possible Solution

Defining a named proc and passing the proc by name works fine.
Using a proc instead of a template works fine.

Additional Information

This bug is only present on the 1.2 branch of Nim.
On 1.4, the bug has been fixed as of 341be0b61cc0603dc921c99b891208dcda274c98.
Backporting said commit on top of 1.2 fixes the bug, but this may introduce breaking changes as the AST representation of procs is modified.

$ nim -v
Nim Compiler Version 1.2.13 [MacOSX: amd64]
Compiled at 2021-08-05
Copyright (c) 2006-2020 by Andreas Rumpf

git hash: 76560576d2dd8ab1876fd4f81029d55467088354
active boot switches: -d:release

metagn commented 2 weeks ago

As mentioned in the issue, works in 1.4 and now