fix JuliaLang#33954, recursion through field types in `is_derived_typ…

…e` (JuliaLang#34223)

base/compiler/typelimits.jl

@@ -57,21 +57,6 @@ function is_derived_type(@nospecialize(t), @nospecialize(c), mindepth::Int)
  for p in cP
  is_derived_type(t, p, mindepth) && return true
  end
- if isconcretetype(c) && isbitstype(c)
- # see if it was extracted from a fieldtype
- # however, only look through types that can be inlined
- # to ensure monotonicity of derivation
- # since we know that for immutable, concrete, bits types,
- # the field types must have been constructed prior to the type,
- # it cannot have a reference cycle in the type graph
- cF = c.types
- for f in cF
- # often a parameter is also a field type; avoid searching twice
- if !contains_is(c.parameters, f)
- is_derived_type(t, f, mindepth) && return true
- end
- end
- end
  end
  return false
 end

src/datatype.c

@@ -306,6 +306,8 @@ static int references_name(jl_value_t *p, jl_typename_t *name) JL_NOTSAFEPOINT
  if (jl_is_datatype(p)) {
  if (((jl_datatype_t*)p)->name == name)
  return 1;
+ if (((jl_datatype_t*)p)->layout && jl_datatype_nfields(p) == 0)
+ return 0;
  size_t i, l = jl_nparams(p);
  for (i = 0; i < l; i++) {
  if (references_name(jl_tparam(p, i), name))
@@ -401,6 +403,7 @@ void jl_compute_field_offsets(jl_datatype_t *st)
  jl_value_t *fld = jl_svecref(w->types, i);
  if (references_name(fld, w->name)) {
  isinlinealloc = 0;
+ isbitstype = 0;
  break;
  }
  }

test/compiler/inference.jl

@@ -2485,3 +2485,10 @@ end
 # constant prop of `Symbol("")`
 f_getf_computed_symbol(p) = getfield(p, Symbol("first"))
 @test Base.return_types(f_getf_computed_symbol, Tuple{Pair{Int8,String}}) == [Int8]
+
+# issue #33954
+struct X33954
+ x::Ptr{X33954}
+end
+f33954(x) = rand(Bool) ? f33954((x,)) : x
+@test Base.return_types(f33954, Tuple{X33954})[1] >: X33954

test/core.jl

@@ -7140,3 +7140,19 @@ end
 struct SplatBadIterate; end
 Base.iterate(s::SplatBadIterate, args...) = ()
 @test_throws BoundsError (SplatBadIterate()...,)
+
+# issue #33954, layout with circular type parameters but not fields
+struct P33954{T}
+end
+struct A33954
+ x::P33954{A33954}
+end
+@test isbitstype(Tuple{A33954})
+struct Q33954{T}
+ x::Int
+end
+struct B33954
+ x::Q33954{B33954}
+end
+@test_broken isbitstype(Tuple{B33954})
+@test_broken isbitstype(B33954)