fix Vararg{T,T} where T crashing code_typed (#56081)

Not sure this is the right place to fix this error, perhaps
`match.spec_types` should always be a tuple of valid types?

fixes #55916

---------

Co-authored-by: Jameson Nash <[email protected]>

Author: simeonschaub

base/compiler/abstractinterpretation.jl

@@ -547,6 +547,7 @@ function collect_slot_refinements(𝕃ᵢ::AbstractLattice, applicable::Vector{A
             sigt = Bottom
             for j = 1:length(applicable)
                 match = applicable[j]::MethodMatch
+                valid_as_lattice(match.spec_types, true) || continue
                 sigt = sigt ⊔ fieldtype(match.spec_types, i)
             end
             if sigt ⊏ argt # i.e. signature type is strictly more specific than the type of the argument slot

test/compiler/inference.jl

@@ -6048,3 +6048,10 @@ t255751 = Array{Float32, 3}
 
 issue55882_nfields(x::Union{T,Nothing}) where T<:Number = nfields(x)
 @test Base.infer_return_type(issue55882_nfields) <: Int
+
+# issue #55916
+f55916(x) = 1
+f55916(::Vararg{T,T}) where {T} = "2"
+g55916(x) = f55916(x)
+# this shouldn't error
+@test only(code_typed(g55916, (Any,); optimize=false))[2] == Int