From 53b21f301effbf407ea7b3c73094d0113ba8d15a Mon Sep 17 00:00:00 2001
From: Simeon David Schaub <simeon@schaub.rocks>
Date: Thu, 10 Oct 2024 12:57:14 +0200
Subject: [PATCH 1/2] fix `Vararg{T,T} where T` crashing `code_typed`

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
---
 base/compiler/abstractinterpretation.jl | 8 +++++++-
 test/compiler/inference.jl              | 7 +++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/base/compiler/abstractinterpretation.jl b/base/compiler/abstractinterpretation.jl
index c8a25be422637..ba11f2cd954b8 100644
--- a/base/compiler/abstractinterpretation.jl
+++ b/base/compiler/abstractinterpretation.jl
@@ -547,7 +547,13 @@ function collect_slot_refinements(𝕃ᵢ::AbstractLattice, applicable::Vector{A
             sigt = Bottom
             for j = 1:length(applicable)
                 match = applicable[j]::MethodMatch
-                sigt = sigt ⊔ fieldtype(match.spec_types, i)
+                spect = fieldtype(match.spec_types, i)
+                if isType(spect)
+                    sigt = sigt ⊔ spect
+                else
+                    sigt = Any
+                    break
+                end
             end
             if sigt ⊏ argt # i.e. signature type is strictly more specific than the type of the argument slot
                 if slotrefinements === nothing
diff --git a/test/compiler/inference.jl b/test/compiler/inference.jl
index 7c7726413004a..e3b1ac499e986 100644
--- a/test/compiler/inference.jl
+++ b/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

From 4319fa9079e40051decfcba1065877b3d1195f99 Mon Sep 17 00:00:00 2001
From: Simeon David Schaub <simeon@schaub.rocks>
Date: Thu, 10 Oct 2024 16:38:19 +0200
Subject: [PATCH 2/2] address review comments

Co-authored-by: Jameson Nash <vtjnash@gmail.com>
---
 base/compiler/abstractinterpretation.jl | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/base/compiler/abstractinterpretation.jl b/base/compiler/abstractinterpretation.jl
index ba11f2cd954b8..70623453e1666 100644
--- a/base/compiler/abstractinterpretation.jl
+++ b/base/compiler/abstractinterpretation.jl
@@ -547,13 +547,8 @@ function collect_slot_refinements(𝕃ᵢ::AbstractLattice, applicable::Vector{A
             sigt = Bottom
             for j = 1:length(applicable)
                 match = applicable[j]::MethodMatch
-                spect = fieldtype(match.spec_types, i)
-                if isType(spect)
-                    sigt = sigt ⊔ spect
-                else
-                    sigt = Any
-                    break
-                end
+                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
                 if slotrefinements === nothing