avoid locking in generated function preamble

Author: MilesCranmer

src/Convert/pyconvert.jl

@@ -309,8 +309,12 @@ pyconvert_fix(::Type{T}, func) where {T} = x -> func(T, x)
 
 const PYCONVERT_RULES_CACHE = Lockable(Dict{Type,Dict{C.PyPtr,Vector{Function}}}())
 
-@generated pyconvert_rules_cache(::Type{T}) where {T} =
-    Base.@lock PYCONVERT_RULES_CACHE get!(Dict{C.PyPtr,Vector{Function}}, PYCONVERT_RULES_CACHE[], T)
+function pyconvert_rules_cache(::Type{T}) where {T}
+    Base.@lock PYCONVERT_RULES_CACHE _pyconvert_rules_cache!(T)
+end
+@generated function _pyconvert_rules_cache!(::Type{T}) where {T}
+    get!(() -> Dict{C.PyPtr,Vector{Function}}(), PYCONVERT_RULES_CACHE[], T)
+end
 
 function pyconvert_rule_fast(::Type{T}, x::Py) where {T}
     if T isa Union