Allow deprecation of curly Exprs

[jiahao]

In #9820 @matrixmorpheus attempted to deprecate the constructor Triangular{S, T, :U, true} which no longer exists on 0.4-dev. However,

julia> @deprecate Triangular{S, T, :U, true} Base.LinAlg.UnitUpperTriangular
ERROR: invalid usage of @deprecate

This error is triggered currently because the expression being deprecated is not currently supported.

julia> dump(:( Triangular{S, T, :U, true}))
Expr 
  head: Symbol curly
  args: Array(Any,(5,))
    1: Symbol Triangular
    2: Symbol S
    3: Symbol T
    4: QuoteNode 
      value: Symbol U
    5: Bool true
  typ: Any

(@deprecate only handles Exprs with head == call currently).

I tried to change this line to add the last || ... clause:

isa(old,Expr) && (old.head == :call || old.head == :curly)

but this resulted in a new error instead when I tried to execute the same @deprecate command:

ERROR: syntax: invalid assignment location

so I'm not sure how to fix this.

[JeffBezanson]

I don't think there is any good way to do this.

[jakebolewski]

Unfortunately this means implementing something along the lines of #8240 would be hugely breaking.

[tkelman]

Does this work now given 1b6efc7 ?

[JeffBezanson]

It works only if just the name changes; we don't have a way to deprecate given combinations of type parameters.

[ViralBShah]

@JeffBezanson Should we close this?

[JeffBezanson]

We don't have this feature, but it's also pretty hard to implement and I have no immediate plans to do it.