Allow using block labels as qualifiers

[metagn]

Abstract

Allow using block labels as qualifiers for symbols defined in them, i.e. block1.proc1.

Motivation

In situations like this, there is no way to disambiguate them (nim-lang/Nim#18785):

proc foo() = echo 1
block:
  proc foo() = echo 2
  foo()
  let x = foo

If we add a label to the block, we could qualify each proc by using the module name for the first proc, and the block label for the second proc.

Description

Not super sure how block labels are implemented, but I think the best way to implement this would be by setting the owner of the defined symbol to the block label symbol, if this is not the case already.

Not sure if module1.proc1 works for symbols defined in blocks. If so, it should be made so they shouldn't.

Code Examples

proc foo() = echo 1
block fooBlock:
  proc foo() = echo 2
  foo()
  modulename.foo()
  fooBlock.foo()
  let x = modulename.foo
  let y = fooBlock.foo

Backwards Compatibility

Macros that extract the modules of symbols using the owner field might have to account for this situation. i.e.

proc findModule(sym: NimNode): NimNode =
  if sym.owner.kind == nskLabel: findModule(sym.owner)
  else: sym.owner

Although they are probably already implemented like this, which should not be affected:

proc findModule(sym: NimNode): NimNode =
  result = sym
  while result.kind != nskModule:
    result = result.owner