Syntax error when referencing Expr objects containing IR-specific content in the REPL

[jrevels]

Might be REPL-only, haven't checked yet. EDIT: Yup, seems to be REPL-only.

Found while trying to update Cassette's reflection/IR pass code for the latest master:

julia> Expr(:call, GlobalRef(Base.Math, :float), Core.SlotNumber(2)) # broken
ERROR: syntax: Slot objects should not occur in an AST

julia> x = Any[Expr(:call, GlobalRef(Base.Math, :float), Core.SlotNumber(2))] # works
1-element Array{Any,1}:
 :((Base.Math.float)(_2))

julia> x[1] # broken
ERROR: syntax: Slot objects should not occur in an AST

julia> begin # works
           x = Expr(:call, GlobalRef(Base.Math, :float), Core.SlotNumber(2))
           y = Any[x]
           z = [y[1]]
       end
1-element Array{Expr,1}:
 :((Base.Math.float)(_2))

[JeffBezanson]

I think this is due to the REPL setting ans by calling eval on an expression containing the value. We could either use another mechanism there, or disable these errors inside QuoteNode.

[jrevels]

Fixed by #27562