diff --git a/base/compiler/ssair/inlining.jl b/base/compiler/ssair/inlining.jl
index f91062f31fb50..a355e0b45c629 100644
--- a/base/compiler/ssair/inlining.jl
+++ b/base/compiler/ssair/inlining.jl
@@ -577,11 +577,11 @@ function ir_inline_unionsplit!(compact::IncrementalCompact, idx::Int, argexprs::
         @assert nparams == fieldcount(mtype)
         if !(i == ncases && fully_covered)
             for i = 1:nparams
-                a, m = fieldtype(atype, i), fieldtype(mtype, i)
+                aft, mft = fieldtype(atype, i), fieldtype(mtype, i)
                 # If this is always true, we don't need to check for it
-                a <: m && continue
+                aft <: mft && continue
                 # Generate isa check
-                isa_expr = Expr(:call, isa, argexprs[i], m)
+                isa_expr = Expr(:call, isa, argexprs[i], mft)
                 ssa = insert_node_here!(compact, NewInstruction(isa_expr, Bool, line))
                 if cond === true
                     cond = ssa
@@ -600,10 +600,10 @@ function ir_inline_unionsplit!(compact::IncrementalCompact, idx::Int, argexprs::
             for i = 1:nparams
                 argex = argexprs[i]
                 (isa(argex, SSAValue) || isa(argex, Argument)) || continue
-                a, m = fieldtype(atype, i), fieldtype(mtype, i)
-                if !(a <: m)
+                aft, mft = fieldtype(atype, i), fieldtype(mtype, i)
+                if !(aft <: mft)
                     argexprs′[i] = insert_node_here!(compact,
-                        NewInstruction(PiNode(argex, m), m, line))
+                        NewInstruction(PiNode(argex, mft), mft, line))
                 end
             end
         end
@@ -964,7 +964,8 @@ function analyze_method!(match::MethodMatch, argtypes::Vector{Any},
     if !match.fully_covers
         # type-intersection was not able to give us a simple list of types, so
         # ir_inline_unionsplit won't be able to deal with inlining this
-        if !(spec_types isa DataType && length(spec_types.parameters) == length(argtypes) && !isvarargtype(spec_types.parameters[end]))
+        if !(spec_types isa DataType && length(spec_types.parameters) == npassedargs &&
+             !isvarargtype(spec_types.parameters[end]))
             return nothing
         end
     end
@@ -1374,16 +1375,18 @@ function compute_inlining_cases(@nospecialize(info::CallInfo), flag::UInt32, sig
             joint_effects = merge_effects(joint_effects, info_effects(result, match, state))
             split_fully_covered |= match.fully_covers
             if !validate_sparams(match.sparams)
-                if !match.fully_covers
-                    handled_all_cases = false
-                    continue
-                end
-                if revisit_idx === nothing
-                    revisit_idx = (i, j, all_result_count)
+                if match.fully_covers
+                    if revisit_idx === nothing
+                        revisit_idx = (i, j, all_result_count)
+                    else
+                        handled_all_cases = false
+                        revisit_idx = nothing
+                    end
                 else
                     handled_all_cases = false
-                    revisit_idx = nothing
                 end
+            elseif !(match.spec_types <: match.method.sig) # the requirement for correct union-split
+                handled_all_cases = false
             else
                 handled_all_cases &= handle_any_const_result!(cases,
                     result, match, argtypes, info, flag, state; allow_abstract=true, allow_typevars=false)
@@ -1418,14 +1421,15 @@ function handle_call!(todo::Vector{Pair{Int,Any}},
     cases = compute_inlining_cases(info, flag, sig, state)
     cases === nothing && return nothing
     cases, all_covered, joint_effects = cases
-    handle_cases!(todo, ir, idx, stmt, argtypes_to_type(sig.argtypes), cases,
-        all_covered, joint_effects)
+    atype = argtypes_to_type(sig.argtypes)
+    handle_cases!(todo, ir, idx, stmt, atype, cases, all_covered, joint_effects)
 end
 
 function handle_match!(cases::Vector{InliningCase},
     match::MethodMatch, argtypes::Vector{Any}, @nospecialize(info::CallInfo), flag::UInt32,
     state::InliningState;
-    allow_abstract::Bool, allow_typevars::Bool, volatile_inf_result::Union{Nothing,VolatileInferenceResult})
+    allow_abstract::Bool, allow_typevars::Bool,
+    volatile_inf_result::Union{Nothing,VolatileInferenceResult})
     spec_types = match.spec_types
     allow_abstract || isdispatchtuple(spec_types) || return false
     # We may see duplicated dispatch signatures here when a signature gets widened
@@ -1512,19 +1516,19 @@ function concrete_result_item(result::ConcreteResult, @nospecialize(info::CallIn
 end
 
 function handle_cases!(todo::Vector{Pair{Int,Any}}, ir::IRCode, idx::Int, stmt::Expr,
-    @nospecialize(atype), cases::Vector{InliningCase}, fully_covered::Bool,
+    @nospecialize(atype), cases::Vector{InliningCase}, all_covered::Bool,
     joint_effects::Effects)
     # If we only have one case and that case is fully covered, we may either
     # be able to do the inlining now (for constant cases), or push it directly
     # onto the todo list
-    if fully_covered && length(cases) == 1
+    if all_covered && length(cases) == 1
         handle_single_case!(todo, ir, idx, stmt, cases[1].item)
     elseif length(cases) > 0
         isa(atype, DataType) || return nothing
         for case in cases
             isa(case.sig, DataType) || return nothing
         end
-        push!(todo, idx=>UnionSplit(fully_covered, atype, cases))
+        push!(todo, idx=>UnionSplit(all_covered, atype, cases))
     else
         add_flag!(ir[SSAValue(idx)], flags_for_effects(joint_effects))
     end
diff --git a/test/compiler/inline.jl b/test/compiler/inline.jl
index d4c6659593fe6..cca1072939025 100644
--- a/test/compiler/inline.jl
+++ b/test/compiler/inline.jl
@@ -2159,3 +2159,24 @@ end
 @test !Core.Compiler.is_nothrow(Base.infer_effects(issue53062, (Bool,)))
 @test issue53062(false) == -1
 @test_throws MethodError issue53062(true)
+
+struct Issue52644
+    tuple::Type{<:Tuple}
+end
+issue52644(::DataType) = :DataType
+issue52644(::UnionAll) = :UnionAll
+let ir = Base.code_ircode((Issue52644,); optimize_until="Inlining") do t
+        issue52644(t.tuple)
+    end |> only |> first
+    irfunc = Core.OpaqueClosure(ir)
+    @test irfunc(Issue52644(Tuple{})) === :DataType
+    @test irfunc(Issue52644(Tuple{<:Integer})) === :UnionAll
+end
+issue52644_single(x::DataType) = :DataType
+let ir = Base.code_ircode((Issue52644,); optimize_until="Inlining") do t
+        issue52644_single(t.tuple)
+    end |> only |> first
+    irfunc = Core.OpaqueClosure(ir)
+    @test irfunc(Issue52644(Tuple{})) === :DataType
+    @test_throws MethodError irfunc(Issue52644(Tuple{<:Integer}))
+end