diff --git a/base/compiler/tfuncs.jl b/base/compiler/tfuncs.jl
index 72e02d262ea94..e0033e418ba79 100644
--- a/base/compiler/tfuncs.jl
+++ b/base/compiler/tfuncs.jl
@@ -1749,14 +1749,12 @@ const _tvarnames = Symbol[:_A, :_B, :_C, :_D, :_E, :_F, :_G, :_H, :_I, :_J, :_K,
             push!(tparams, ai.tv)
         else
             uncertain = true
-            # These blocks improve type info but make compilation a bit slower.
-            # XXX
-            #unw = unwrap_unionall(ai)
-            #isT = isType(unw)
-            #if isT && isa(ai,UnionAll) && contains_is(outervars, ai.var)
-            #    ai = rename_unionall(ai)
-            #    unw = unwrap_unionall(ai)
-            #end
+            unw = unwrap_unionall(ai)
+            isT = isType(unw)
+            if isT && isa(ai,UnionAll) && contains_is(outervars, ai.var)
+                ai = rename_unionall(ai)
+                unw = unwrap_unionall(ai)
+            end
             ai_w = widenconst(ai)
             ub = ai_w isa Type && ai_w <: Type ? instanceof_tfunc(ai)[1] : Any
             if istuple
@@ -1764,19 +1762,17 @@ const _tvarnames = Symbol[:_A, :_B, :_C, :_D, :_E, :_F, :_G, :_H, :_I, :_J, :_K,
                 # then this could be a Vararg type.
                 if i == largs && ub === Any
                     push!(tparams, Vararg)
-                # XXX
-                #elseif isT
-                #    push!(tparams, rewrap_unionall(unw.parameters[1], ai))
+                elseif isT
+                    push!(tparams, rewrap_unionall(unw.parameters[1], ai))
                 else
                     push!(tparams, Any)
                 end
-            # XXX
-            #elseif isT
-            #    push!(tparams, unw.parameters[1])
-            #    while isa(ai, UnionAll)
-            #        push!(outervars, ai.var)
-            #        ai = ai.body
-            #    end
+            elseif isT
+                push!(tparams, unw.parameters[1])
+                while isa(ai, UnionAll)
+                    push!(outervars, ai.var)
+                    ai = ai.body
+                end
             else
                 # Is this the second parameter to a NamedTuple?
                 if isa(uw, DataType) && uw.name === _NAMEDTUPLE_NAME && isa(ua, UnionAll) && uw.parameters[2] === ua.var
diff --git a/test/compiler/inference.jl b/test/compiler/inference.jl
index b7adcba297925..9d6446496e132 100644
--- a/test/compiler/inference.jl
+++ b/test/compiler/inference.jl
@@ -4643,6 +4643,16 @@ end
     end)[2] === Nothing
 end
 
+# `apply_type_tfunc` accuracy for constrained type construction
+# https://github.com/JuliaLang/julia/issues/47089
+import Core: Const
+import Core.Compiler: apply_type_tfunc
+struct Issue47089{A,B} end
+let A = Type{<:Integer}
+    @test apply_type_tfunc(Const(T), A, A) <: (Type{T{A,B}} where {A<:Integer, B<:Integer})
+end
+@test only(Base.return_types(keys, (Dict{String},))) == Base.KeySet{String, T} where T<:(Dict{String})
+
 # singleton_type on slot wrappers
 @test Base.return_types((Int,)) do x
     c = isa(x, Int) # ::Conditional