when a() and b() should short-circuit semcheck

[timotheecour]

when declared(Foo) and T is Foo: fails but there's no reason to: and should short-circuit semcheck of 2nd arg when 1st arg is false

Example

type T = int
static: doAssert not declared(Foo) # ok
# all these fail with: Error: undeclared identifier: 'Foo'
when declared(Foo) and T is Foo: discard
when false and T is Foo: discard
const isFoo1 = declared(Foo) and (T is Foo)
const isFoo2 = false and (T is Foo)

Current Output

Error: undeclared identifier: 'Foo'

Expected Output

works.

in particular, this is useful for eg in generic code in include files etc where you need to specialize for some types, but these may not be present

workaround

  template ctAnd(a, b): bool =
    when a:
      when b: true
      else: false
    else: false

  type T = int
  type Bar = int
  static: doAssert not ctAnd(declared(Foo), T is Foo)
  static: doAssert ctAnd(declared(Bar), T is Bar)
  static: doAssert not ctAnd(declared(Bar), T isnot Bar)

Additional Information

• 3dad130 devel 1.1.1

[krux02]

what you want is short circuit semantic checking not short circuit evaluation. The later one already happens. And btw -1 for the feature request.

[Araq]

This is a bug, not a feature request. In fact, it's a duplicate of some other bug report.

[Araq]

I take it back, I misunderstood this problem. This is not a bug, the sem'checking for and follows Nim's basic rules and it's overloaded even, so no ``untyped´`-like behaviour is desired.