diff --git a/src/types-analysis/data.jl b/src/types-analysis/data.jl
index bf305be..20cfe9c 100644
--- a/src/types-analysis/data.jl
+++ b/src/types-analysis/data.jl
@@ -34,8 +34,12 @@ SplitFunDef = Dict{Symbol, Any}
 # Analyzing type annotations
 #%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-"Kind of type constructor"
-@enum TypeConstructor TCTuple TCInvar TCUnion TCWhere TCLoBnd TCUpBnd TCVar
+"""
+Kind of type constructor
+- TCVar means that the variable is used as a target of {}, e.g. X{Int} where X
+- TCLBVar1 means that the variable has a single anonymous usage in lower bound, e.g. Ref{>:Int}
+"""
+@enum TypeConstructor TCTuple TCInvar TCUnion TCWhere TCLoBnd TCUpBnd TCVar TCLBVar1 TCUBVar1
 
 "Stack of type constructors"
 TypeConstrStack = LinkedList{TypeConstructor}
diff --git a/src/types-analysis/type-analyze.jl b/src/types-analysis/type-analyze.jl
index bd4293e..f99cc37 100644
--- a/src/types-analysis/type-analyze.jl
+++ b/src/types-analysis/type-analyze.jl
@@ -6,7 +6,71 @@
 #
 #######################################################################
 
-const ANONYMOUS_TYPE_VARIABLE = :ANON_TV
+const ANONYMOUS_TY_VAR = :ANON_TV
+
+#%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+# Analyzing type variable summaries for restrictions
+#%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+
+tyVarRestrictedScopePreserved(tytvs :: TypeTyVarsSummary) = 
+    all(tyVarRestrictedScopePreserved, tytvs)
+
+tyVarRestrictedScopePreserved(tvs :: TyVarSummary) = 
+    all(tyVarRestrictedScopePreserved, map(reverse, tvs.occurrs))
+
+tyVarRestrictedScopePreserved(
+    constrStack :: Nil{TypeConstructor}; invarCrossed :: Bool = false
+) = true
+tyVarRestrictedScopePreserved(
+    constrStack :: Cons{TypeConstructor}; invarCrossed :: Bool = false
+) = begin
+    (hd, tl) = (head(constrStack), tail(constrStack))
+    if hd == TCInvar || hd == TCLoBnd || hd == TCLBVar1
+        tyVarRestrictedScopePreserved(tl; invarCrossed = true)
+    elseif hd == TCWhere || hd == TCLoBnd || hd == TCUpBnd || hd == TCUnion 
+        invarCrossed ? false : tyVarRestrictedScopePreserved(tl)
+    else 
+        tyVarRestrictedScopePreserved(tl)
+    end
+end
+
+
+tyVarOccursAsUsedSiteVariance(tytvs :: TypeTyVarsSummary) = 
+    all(tyVarOccursAsUsedSiteVariance, tytvs)
+
+"""
+For wildcards-like restriction, type variable can be used only once
+in an invariant or cotravariant position
+"""
+tyVarOccursAsUsedSiteVariance(tvs :: TyVarSummary) = begin
+    covOccs = count(tyVarOccIsCovariant, map(reverse, tvs.occurrs))
+    # either all occurrences are covariant, or there is only one
+    # non-covariant occurrence
+    covOccs == length(tvs.occurrs) || 
+    length(tvs.occurrs) == 1 && tyVarNonCovOccIsImmediate(reverse(tvs.occurrs[1]))
+end
+
+tyVarOccIsCovariant(constrStack :: Nil{TypeConstructor}) = true
+tyVarOccIsCovariant(constrStack :: Cons{TypeConstructor}) =
+    head(constrStack) in [TCTuple, TCUnion, TCWhere, TCUpBnd, TCUBVar1] &&
+    tyVarOccIsCovariant(tail(constrStack))
+
+tyVarNonCovOccIsImmediate(constrStack :: Nil{TypeConstructor}) = true
+tyVarNonCovOccIsImmediate(constrStack :: Cons{TypeConstructor}) = 
+    head(constrStack) in [TCTuple, TCUnion, TCWhere, TCUpBnd, TCUBVar1] ||
+    isempty(tail(constrStack))
+
+
+"No more than once"
+tyVarUsedOnce(tytvs :: TypeTyVarsSummary) = 
+    all(tyVarUsedOnce, tytvs)
+
+tyVarUsedOnce(tvs :: TyVarSummary) = length(tvs.occurrs) <= 1
+
+#%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+# Summarizing type variable usage
+#%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 collectTyVarsSummary(ty :: JlASTTypeExpr) = 
     collectTyVarsSummary!(ty, envempty(), TypeTyVarsSummary())
@@ -21,15 +85,6 @@ collectTyVarsSummary!(
     env :: TyVarEnv, tvsumm :: TypeTyVarsSummary
 ) = throw(TypesAnlsUnsupportedTypeAnnotation(ty))
 
-#=
-collectTyVarsSummary!(
-    ty :: JlASTTypeExpr,
-    env :: TyVarEnv, tvsumm :: TypeTyVarsSummary
-) = begin
-    
-end
-=#
-
 """
 Symbol may represent a variable occurrence
 """
@@ -58,6 +113,20 @@ collectTyVarsSummary!(
     elseif ty.head == :curly
         @assert length(ty.args) >= 1 "Unsupported {} $ty"
         collectTyVarsSummaryCurly!(ty.args, env, tvsumm)
+    elseif ty.head == :(<:) # Ref{<:ub}
+        @assert length(ty.args) == 1 "Unsupported short-hand <: $ty"
+        envUB = envpushconstr(env, TCUpBnd)
+        collectTyVarsSummary!(ty.args[1], envUB, tvsumm)
+        push!(tvsumm,
+            TyVarSummary(ANONYMOUS_TY_VAR, DEFAULT_LB, ty.args[1], [list(TCUBVar1)]))
+        tvsumm
+    elseif ty.head == :(>:) # Ref{>:lb}
+        @assert length(ty.args) == 1 "Unsupported short-hand >: $ty"
+        envLB = envpushconstr(env, TCLoBnd)
+        collectTyVarsSummary!(ty.args[1], envLB, tvsumm)
+        push!(tvsumm,
+            TyVarSummary(ANONYMOUS_TY_VAR, ty.args[1], DEFAULT_UB, [list(TCLBVar1)]))
+        tvsumm
     else
         throw(TypesAnlsUnsupportedTypeAnnotation(ty))
     end
@@ -88,7 +157,7 @@ splitTyVarDecl(tvDecl :: Symbol) =
     (tvDecl, DEFAULT_LB, DEFAULT_UB)
 
 splitTyVarDecl(tvDecl :: Expr) = begin
-    name = ANONYMOUS_TYPE_VARIABLE
+    name = ANONYMOUS_TY_VAR
     lb = DEFAULT_LB
     ub = DEFAULT_UB
     if tvDecl.head == :(<:)
@@ -110,7 +179,7 @@ end
 
 tyVarDeclIsComparison(tvDecl :: Expr) = tvDecl.head == :comparison && 
     length(tvDecl.args) == 5 && tvDecl.args[3] isa Symbol &&
-    tvDecl.args[2] == :(<:) && tvDecl.args[4] == :(>:)
+    tvDecl.args[2] == :(<:) && tvDecl.args[4] == :(<:)
 
 #--------------------------------------------------
 # ...{...} type
diff --git a/test/types-analysis.jl b/test/types-analysis.jl
index a80202b..522bd6a 100644
--- a/test/types-analysis.jl
+++ b/test/types-analysis.jl
@@ -10,9 +10,10 @@ using Main.JuliaSub: collectFunDefTypeAnnotations, collectTypeAnnotations
 using Main.JuliaSub: parseAndCollectTypeAnnotations
 
 using Main.JuliaSub: TyVarSummary, TypeTyVarsSummary
-using Main.JuliaSub: DEFAULT_LB, DEFAULT_UB, tcsempty
-using Main.JuliaSub: TCTuple, TCInvar, TCUnion, TCWhere, TCLoBnd, TCUpBnd, TCVar
+using Main.JuliaSub: DEFAULT_LB, DEFAULT_UB, tcsempty, ANONYMOUS_TY_VAR
+using Main.JuliaSub: TCTuple, TCInvar, TCUnion, TCWhere, TCLoBnd, TCUpBnd, TCVar, TCLBVar1, TCUBVar1
 using Main.JuliaSub: collectTyVarsSummary
+using Main.JuliaSub: tyVarRestrictedScopePreserved, tyVarOccursAsUsedSiteVariance, tyVarUsedOnce
 
 #%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 # Aux values and functions
@@ -213,21 +214,71 @@ end
                 ]),
         ]
 
-    #=
-    @test parseAndCollectTypeAnnotations(
-            testFilePath("Multisets-cut.jl")
-        ) == list(
-            TypeAnnInfo(:push!, mtsig, :( Tuple{Multiset{T}, Any, Int} where T )),
-            TypeAnnInfo(:getindex, mtsig, :( Tuple{Multiset{T}, Any} where T )),
-            TypeAnnInfo(:clean!, mtsig, :( Tuple{Multiset} )),
-            TypeAnnInfo(:Multiset, mtsig, :( Tuple{Base.AbstractSet{T}} where T )),
-            TypeAnnInfo(:Multiset, mtsig, :(( Tuple{AbstractArray{T, d}} where d) where T )), 
-            TypeAnnInfo(:eltype, mtsig, :( Tuple{Multiset{T}} where T )),
-            TypeAnnInfo(:(Base.empty!), mtsig, :( Tuple{Multiset{T}} where T )),
-            TypeAnnInfo(:(Base.copy), mtsig, :( Tuple{Multiset{T}} where T )),
-            TypeAnnInfo(:Multiset, mtsig, :( Tuple{Vararg{Any}} )),
-            TypeAnnInfo(:Multiset, mtsig, :( Tuple{} )),
-            TypeAnnInfo(:Multiset, mtsig, :( Tuple{} where T ))
-        )
-    =#
+    @test collectTyVarsSummary(:(Pair{<:Number, T} where Int<:T<:Foo{>:Int})) == [
+        TyVarSummary(ANONYMOUS_TY_VAR, :Int, DEFAULT_UB, [list(TCLBVar1)]),
+        TyVarSummary(ANONYMOUS_TY_VAR, DEFAULT_LB, :Number, [list(TCUBVar1)]),
+        TyVarSummary(:T, :Int, :(Foo{>:Int}), [list(TCInvar)]),
+    ]
 end
+
+@testset "types-analysis :: analysis of type vars usage " begin
+    tvsInt = collectTyVarsSummary(:(Int))
+    @test tyVarUsedOnce(tvsInt)
+    @test tyVarOccursAsUsedSiteVariance(tvsInt)
+    @test tyVarRestrictedScopePreserved(tvsInt)
+
+    tvsVector = collectTyVarsSummary(:(Vector{T} where T))
+    @test tyVarUsedOnce(tvsVector)
+    @test tyVarOccursAsUsedSiteVariance(tvsVector)
+    @test tyVarRestrictedScopePreserved(tvsVector)
+
+    tvsPair = collectTyVarsSummary(:(Pair{T, T} where T))
+    @test !tyVarUsedOnce(tvsPair)
+    @test !tyVarOccursAsUsedSiteVariance(tvsPair)
+    @test tyVarRestrictedScopePreserved(tvsPair)
+
+    tvsTuple = collectTyVarsSummary(:(Tuple{T, Tuple{T, Int}} where T))
+    @test !tyVarUsedOnce(tvsTuple)
+    @test tyVarOccursAsUsedSiteVariance(tvsTuple)
+    @test tyVarRestrictedScopePreserved(tvsTuple)
+
+    tvsTupleRef = collectTyVarsSummary(:(Tuple{T, Ref{T}} where T))
+    @test !tyVarUsedOnce(tvsTupleRef)
+    @test !tyVarOccursAsUsedSiteVariance(tvsTupleRef)
+    @test tyVarRestrictedScopePreserved(tvsTupleRef)
+
+    tvsRefUnion = collectTyVarsSummary(:(Vector{Union{T, Int}} where T))
+    @test tyVarUsedOnce(tvsRefUnion)
+    @test !tyVarOccursAsUsedSiteVariance(tvsRefUnion)
+    @test !tyVarRestrictedScopePreserved(tvsRefUnion)
+
+    tvsRefWhereRef = collectTyVarsSummary(:(Ref{Ref{T} where T} where T))
+    @test tyVarUsedOnce(tvsRefWhereRef)
+    @test tyVarOccursAsUsedSiteVariance(tvsRefWhereRef)
+    @test tyVarRestrictedScopePreserved(tvsRefWhereRef)
+
+    tvsRefWherePair = collectTyVarsSummary(:(Ref{Pair{T, S} where S} where T))
+    @test tyVarUsedOnce(tvsRefWherePair)
+    @test !tyVarOccursAsUsedSiteVariance(tvsRefWherePair)
+    @test tyVarOccursAsUsedSiteVariance(tvsRefWherePair[1]) # S
+    @test !tyVarOccursAsUsedSiteVariance(tvsRefWherePair[2]) # T
+    @test !tyVarRestrictedScopePreserved(tvsRefWherePair)
+    @test tyVarRestrictedScopePreserved(tvsRefWherePair[1]) # S
+    @test !tyVarRestrictedScopePreserved(tvsRefWherePair[2]) # T
+
+    tvsPairWherePair = collectTyVarsSummary(:(Pair{S, Pair{Int, T} where T<:S} where S))
+    @test !tyVarUsedOnce(tvsPairWherePair)
+    @test tyVarUsedOnce(tvsPairWherePair[1]) # T
+    @test !tyVarUsedOnce(tvsPairWherePair[2]) # S
+    @test !tyVarOccursAsUsedSiteVariance(tvsPairWherePair)
+    @test tyVarOccursAsUsedSiteVariance(tvsPairWherePair[1]) # T
+    @test !tyVarOccursAsUsedSiteVariance(tvsPairWherePair[2]) # S
+    @test !tyVarRestrictedScopePreserved(tvsPairWherePair)
+    @test tyVarRestrictedScopePreserved(tvsPairWherePair[1]) # T
+    @test !tyVarRestrictedScopePreserved(tvsPairWherePair[2]) # S
+
+    tvsTupleWherePair = collectTyVarsSummary(:(Tuple{S, Pair{T, S} where T<:S} where S))
+    @test !tyVarUsedOnce(tvsTupleWherePair)
+    @test !tyVarOccursAsUsedSiteVariance(tvsTupleWherePair)
+    @test tyVarRestrictedScopePreserved(tvsTupleWherePair)
+end
\ No newline at end of file