diff --git a/base/compiler/ssair/inlining.jl b/base/compiler/ssair/inlining.jl
index 17141cf8eaec7..09c550b09029d 100644
--- a/base/compiler/ssair/inlining.jl
+++ b/base/compiler/ssair/inlining.jl
@@ -57,7 +57,7 @@ struct InvokeCase
 end
 
 struct InliningCase
-    sig  # ::Type
+    sig  # Type
     item # Union{InliningTodo, MethodInstance, ConstantCase}
     function InliningCase(@nospecialize(sig), @nospecialize(item))
         @assert isa(item, Union{InliningTodo, InvokeCase, ConstantCase}) "invalid inlining item"
@@ -67,10 +67,10 @@ end
 
 struct UnionSplit
     fully_covered::Bool
-    atype # ::Type
+    atype::DataType
     cases::Vector{InliningCase}
     bbs::Vector{Int}
-    UnionSplit(fully_covered::Bool, atype, cases::Vector{InliningCase}) =
+    UnionSplit(fully_covered::Bool, atype::DataType, cases::Vector{InliningCase}) =
         new(fully_covered, atype, cases, Int[])
 end
 
@@ -474,12 +474,11 @@ function ir_inline_unionsplit!(compact::IncrementalCompact, idx::Int,
     @assert length(bbs) >= length(cases)
     for i in 1:length(cases)
         ithcase = cases[i]
-        metharg = ithcase.sig
+        metharg = ithcase.sig::DataType # checked within `handle_cases!`
         case = ithcase.item
         next_cond_bb = bbs[i]
-        @assert isa(metharg, DataType)
         cond = true
-        aparams, mparams = atype.parameters::SimpleVector, metharg.parameters::SimpleVector
+        aparams, mparams = atype.parameters, metharg.parameters
         @assert length(aparams) == length(mparams)
         if i != length(cases) || !fully_covered ||
                 (!params.trust_inference && isdispatchtuple(cases[i].sig))
@@ -1222,7 +1221,6 @@ function analyze_single_call!(
         end
     end
 
-
     atype = argtypes_to_type(argtypes)
     if handled_all_cases && revisit_idx !== nothing
         # If there's only one case that's not a dispatchtuple, we can
@@ -1234,7 +1232,7 @@ function analyze_single_call!(
         # cases are split off from an ::Any typed fallback.
         (i, j) = revisit_idx
         match = infos[i].results[j]
-        handled_all_cases &= handle_match!(match, argtypes, flag, state, cases)
+        handled_all_cases &= handle_match!(match, argtypes, flag, state, cases, true)
     elseif length(cases) == 0 && only_method isa Method
         # if the signature is fully covered and there is only one applicable method,
         # we can try to inline it even if the signature is not a dispatch tuple.
@@ -1248,9 +1246,7 @@ function analyze_single_call!(
             @assert length(meth) == 1
             match = meth[1]
         end
-        item = analyze_method!(match, argtypes, flag, state)
-        item === nothing && return nothing
-        push!(cases, InliningCase(match.spec_types, item))
+        handle_match!(match, argtypes, flag, state, cases, true) || return nothing
         any_covers_full = handled_all_cases = match.fully_covers
     end
 
@@ -1290,7 +1286,7 @@ function handle_const_call!(
                 handled_all_cases &= handle_inf_result!(result, argtypes, flag, state, cases)
             else
                 @assert result === nothing
-                handled_all_cases &= isdispatchtuple(match.spec_types) && handle_match!(match, argtypes, flag, state, cases)
+                handled_all_cases &= handle_match!(match, argtypes, flag, state, cases)
             end
         end
     end
@@ -1298,13 +1294,13 @@ function handle_const_call!(
     # if the signature is fully covered and there is only one applicable method,
     # we can try to inline it even if the signature is not a dispatch tuple
     atype = argtypes_to_type(argtypes)
-    if length(cases) == 0 && length(results) == 1 && isa(results[1], InferenceResult)
-        (; mi) = item = InliningTodo(results[1]::InferenceResult, argtypes)
-        state.mi_cache !== nothing && (item = resolve_todo(item, state, flag))
-        validate_sparams(mi.sparam_vals) || return nothing
-        item === nothing && return nothing
-        push!(cases, InliningCase(mi.specTypes, item))
-        any_covers_full = handled_all_cases = atype <: mi.specTypes
+    if length(cases) == 0
+        length(results) == 1 || return nothing
+        result = results[1]
+        isa(result, InferenceResult) || return nothing
+        handle_inf_result!(result, argtypes, flag, state, cases, true) || return nothing
+        spec_types = cases[1].sig
+        any_covers_full = handled_all_cases = atype <: spec_types
     end
 
     handle_cases!(ir, idx, stmt, atype, cases, any_covers_full && handled_all_cases, todo, state.params)
@@ -1312,8 +1308,9 @@ end
 
 function handle_match!(
     match::MethodMatch, argtypes::Vector{Any}, flag::UInt8, state::InliningState,
-    cases::Vector{InliningCase})
+    cases::Vector{InliningCase}, allow_abstract::Bool = false)
     spec_types = match.spec_types
+    allow_abstract || isdispatchtuple(spec_types) || return false
     item = analyze_method!(match, argtypes, flag, state)
     item === nothing && return false
     _any(case->case.sig === spec_types, cases) && return true
@@ -1323,10 +1320,10 @@ end
 
 function handle_inf_result!(
     result::InferenceResult, argtypes::Vector{Any}, flag::UInt8, state::InliningState,
-    cases::Vector{InliningCase})
+    cases::Vector{InliningCase}, allow_abstract::Bool = false)
     (; mi) = item = InliningTodo(result, argtypes)
     spec_types = mi.specTypes
-    isdispatchtuple(spec_types) || return false
+    allow_abstract || isdispatchtuple(spec_types) || return false
     validate_sparams(mi.sparam_vals) || return false
     state.mi_cache !== nothing && (item = resolve_todo(item, state, flag))
     item === nothing && return false
@@ -1351,6 +1348,8 @@ function handle_cases!(ir::IRCode, idx::Int, stmt::Expr, @nospecialize(atype),
     if fully_covered && length(cases) == 1
         handle_single_case!(ir, idx, stmt, cases[1].item, todo, params)
     elseif length(cases) > 0
+        isa(atype, DataType) || return nothing
+        all(case::InliningCase->isa(case.sig, DataType), cases) || return nothing
         push!(todo, idx=>UnionSplit(fully_covered, atype, cases))
     end
     return nothing