Feature request: Constant-fold keyword arguments somehow

[jakobnissen]

Minimal example

julia> function foo(x::Integer, y::Bool=(x isa Int))
           if y
               x * "string"
           else
               x + one(x)
           end
       end
foo (generic function with 2 methods)

julia> @report_call foo(0x01)
═════ 1 possible error found ═════
┌ @ REPL[4]:2 #self#(x, Main.isa(x, Main.Int))
│┌ @ REPL[4]:3 Main.*(x, "string")
││ no matching method found for call signature (Tuple{typeof(*), UInt8, String}): Main.*(x::UInt8, "string")
│└─────────────

The error showed can in fact never happen, since in the call f(0x01), y statically should resolve to false.
I have no idea whether this kind of constant prop is feasible, either in Julia's compiler itself, or in JET.

This is on Julia 1.7-rc1.

[jakobnissen]

Okay, I just now realized that my minimal example doesn't work! Let me close until I fix it
Updated example

[jakobnissen]

It's in Base Julia: JuliaLang/julia#42449

[aviatesk]

Fixed by JuliaLang/julia#42529.