diff --git a/test/ambiguous.jl b/test/ambiguous.jl
index bad5f19f389c9..8d0c2092f21c2 100644
--- a/test/ambiguous.jl
+++ b/test/ambiguous.jl
@@ -369,4 +369,21 @@ let ambig = Int32[0]
     @test ambig[1] == 1
 end
 
+# issue #11407
+f11407(::Dict{K,V}, ::Dict{Any,V}) where {K,V} = 1
+f11407(::Dict{K,V}, ::Dict{K,Any}) where {K,V} = 2
+@test_throws MethodError f11407(Dict{Any,Any}(), Dict{Any,Any}()) # ambiguous
+@test f11407(Dict{Any,Int}(), Dict{Any,Int}()) == 1
+f11407(::Dict{Any,Any}, ::Dict{Any,Any}) where {K,V} = 3
+@test f11407(Dict{Any,Any}(), Dict{Any,Any}()) == 3
+
+# issue #12814
+abstract type A12814{N, T} end
+struct B12814{N, T} <: A12814{N, T}
+    x::NTuple{N, T}
+end
+(::Type{T})(x::X) where {T <: A12814, X <: Array} = 1
+@test_throws MethodError B12814{3, Float64}([1, 2, 3]) # ambiguous
+@test B12814{3,Float64}((1, 2, 3)).x === (1.0, 2.0, 3.0)
+
 nothing
diff --git a/test/subtype.jl b/test/subtype.jl
index 6956c212301ea..244ce3c4b7900 100644
--- a/test/subtype.jl
+++ b/test/subtype.jl
@@ -1901,3 +1901,16 @@ let A = Tuple{Array{Pair{T, JT} where JT<:Ref{T}, 1} where T, Vector},
     @test_broken I <: A
     @test_broken !Base.has_free_typevars(I)
 end
+
+# issue #8915
+struct D8915{T<:Union{Float32,Float64}}
+    D8915{T}(a) where {T} = 1
+    D8915{T}(a::Int) where {T} = 2
+end
+@test D8915{Float64}(1) == 2
+@test D8915{Float64}(1.0) == 1
+
+# issue #18985
+f18985(x::T, y...) where {T<:Union{Int32,Int64}} = (length(y), f18985(y[1], y[2:end]...)...)
+f18985(x::T) where {T<:Union{Int32,Int64}} = 100
+@test f18985(1, 2, 3) == (2, 1, 100)