StackOverflowError on a push! into a Dict

[jcampolongo]

The creation of a dictionary with a key of type Tuple{Type{<:Real}} causes a StackOverflowError on a push!. This occurs on both 1.5.0 and 1.5.1 versions of Julia (on windows).

julia> d = Dict{Tuple{Type{<:Real}},Int64}()
Dict{Tuple{Type{var"#s2248"} where var"#s2248"<:Real},Int64}()
julia> push!(d, (Int64,)=>10)
ERROR: StackOverflowError:
Stacktrace:
 [1] convert(::Type{Tuple{Type{var"#s2247"} where var"#s2247"<:Real}}, ::Tuple{DataType}) at .\essentials.jl:310
 [2] setindex!(::Dict{Tuple{Type{var"#s2248"} where var"#s2248"<:Real},Int64}, ::Int64, ::Tuple{DataType}) at .\dict.jl:372
 [3] setindex!(::Dict{Tuple{Type{var"#s2248"} where var"#s2248"<:Real},Int64}, ::Int64, ::Tuple{DataType}) at .\dict.jl:376 (repeats 29007 times)
 [4] push!(::Dict{Tuple{Type{var"#s2248"} where var"#s2248"<:Real},Int64}, ::Pair{Tuple{DataType},Int64}) at .\abstractdict.jl:510
 [5] top-level scope at REPL[150]:1

Using a Type{<:Real} does not have this issue.

julia> d = Dict{Type{<:Real}, Int64}()
Dict{Type{var"#s2249"} where var"#s2249"<:Real,Int64}()
julia> push!(d, Int64=>10)
Dict{Type{var"#s2249"} where var"#s2249"<:Real,Int64} with 1 entry:
  Int64 => 10

Version Information

julia> versioninfo()
Julia Version 1.5.1
Commit 697e782ab8 (2020-08-25 20:08 UTC)
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: Intel(R) Xeon(R) W-2135 CPU @ 3.70GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-9.0.1 (ORCJIT, skylake-avx512)

[vtjnash]

The issue is that convert(Tuple{...}, x) doesn't guarantee that the result is of type T (mostly because NamedTuples now rely upon it), so it's not getting the expected type, and just tries (and fails) repeatedly. I tried this patch, but it runs into inference problem (an incorrect answer by the typeassert_tfunc tuple_tfunc)

diff --git a/base/dict.jl b/base/dict.jl
index cc5c9efb6a..9628285bf4 100644
--- a/base/dict.jl
+++ b/base/dict.jl
@@ -373,3 +373,3 @@ end
 function setindex!(h::Dict{K,V}, v0, key0) where V where K
-    key = convert(K, key0)
+    key = convert(K, key0)::K
     if !isequal(key, key0)
@@ -381,3 +381,3 @@ end
 function setindex!(h::Dict{K,V}, v0, key::K) where V where K
-    v = convert(V, v0)
+    v = convert(V, v0)::V
     index = ht_keyindex2!(h, key)
@@ -451,3 +451,3 @@ get!(f::Function, collection, key)
 function get!(default::Callable, h::Dict{K,V}, key0) where V where K
-    key = convert(K, key0)
+    key = convert(K, key0)::K
     if !isequal(key, key0)
@@ -464,3 +464,3 @@ function get!(default::Callable, h::Dict{K,V}, key::K) where V where K
     age0 = h.age
-    v = convert(V, default())
+    v = convert(V, default())::V
     if h.age != age0