From b8d81c78cbce6b588b73d77190a11ef27818564b Mon Sep 17 00:00:00 2001
From: Pablo Zubieta <pabloferz@yahoo.com.mx>
Date: Sun, 29 Jan 2017 16:04:37 -0600
Subject: [PATCH 1/2] Improve inferability of unique

---
 base/set.jl  | 30 +++++++++++++++++++++++++-----
 test/sets.jl |  3 +++
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/base/set.jl b/base/set.jl
index 55ba8bab1fff0..e6831bfaf4fe6 100644
--- a/base/set.jl
+++ b/base/set.jl
@@ -123,16 +123,36 @@ julia> unique([1; 2; 2; 6])
  6
 ```
 """
-function unique(C)
-    out = Vector{eltype(C)}()
-    seen = Set{eltype(C)}()
-    for x in C
+function unique(itr)
+    T = _default_eltype(typeof(itr))
+    out = Vector{T}()
+    seen = Set{T}()
+    i = start(itr)
+    if done(itr, i)
+        return out
+    end
+    x, i = next(itr, i)
+    if !isleaftype(T)
+        T = typeof(x)
+        out = Vector{T}()
+        seen = Set{T}()
+    end
+    push!(seen, x)
+    push!(out, x)
+    while !done(itr, i)
+        x, i = next(itr, i)
+        S = typeof(x)
+        if !(S === T || S <: T)
+            T = typejoin(S, T)
+            seen = convert(Set{T}, seen)
+            out = convert(Vector{T}, out)
+        end
         if !in(x, seen)
             push!(seen, x)
             push!(out, x)
         end
     end
-    out
+    return out
 end
 
 """
diff --git a/test/sets.jl b/test/sets.jl
index f57c7bd9ff24d..c5abf4df21308 100644
--- a/test/sets.jl
+++ b/test/sets.jl
@@ -212,6 +212,9 @@ u = unique([1,1,2])
 @test length(u) == 2
 @test unique(iseven, [5,1,8,9,3,4,10,7,2,6]) == [5,8]
 @test unique(n->n % 3, [5,1,8,9,3,4,10,7,2,6]) == [5,1,9]
+# issue 20105
+@test @inferred(unique(x for x in 1:1)) == [1]
+@test unique(x for x in Any[1,1.0])::Vector{Real} == [1]
 
 # allunique
 @test allunique([])

From 432478d311a141e521074ffb9b3721ff5521cc73 Mon Sep 17 00:00:00 2001
From: Pablo Zubieta <pabloferz@yahoo.com.mx>
Date: Wed, 1 Feb 2017 14:26:04 -0600
Subject: [PATCH 2/2] Put unique loop in another function

---
 base/set.jl | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/base/set.jl b/base/set.jl
index e6831bfaf4fe6..df98cb43174ab 100644
--- a/base/set.jl
+++ b/base/set.jl
@@ -133,19 +133,28 @@ function unique(itr)
     end
     x, i = next(itr, i)
     if !isleaftype(T)
-        T = typeof(x)
-        out = Vector{T}()
-        seen = Set{T}()
+        S = typeof(x)
+        return _unique_from(itr, S[x], Set{S}((x,)), i)
     end
     push!(seen, x)
     push!(out, x)
+    return unique_from(itr, out, seen, i)
+end
+
+_unique_from(itr, out, seen, i) = unique_from(itr, out, seen, i)
+@inline function unique_from{T}(itr, out::Vector{T}, seen, i)
     while !done(itr, i)
         x, i = next(itr, i)
         S = typeof(x)
         if !(S === T || S <: T)
-            T = typejoin(S, T)
-            seen = convert(Set{T}, seen)
-            out = convert(Vector{T}, out)
+            R = typejoin(S, T)
+            seenR = convert(Set{R}, seen)
+            outR = convert(Vector{R}, out)
+            if !in(x, seenR)
+                push!(seenR, x)
+                push!(outR, x)
+            end
+            return _unique_from(itr, outR, seenR, i)
         end
         if !in(x, seen)
             push!(seen, x)