Use three-valued logic with missing values in ==(::Tuple, ::Tuple)

For consistency with AbstractArray.

Author: nalimilan

base/tuple.jl

@@ -268,12 +268,16 @@ function ==(t1::Tuple, t2::Tuple)
     if length(t1) != length(t2)
         return false
     end
+    anymissing = false
     for i = 1:length(t1)
-        if !(t1[i] == t2[i])
-            return false
-        end
+        eq = (t1[i] == t2[i])
+        if ismissing(eq)
+            anymissing = true
+        elseif !eq
+           return false
+       end
     end
-    return true
+    return anymissing ? missing : true
 end
 
 const tuplehash_seed = UInt === UInt64 ? 0x77cfa1eef01bca90 : 0xf01bca90

test/missing.jl

@@ -222,6 +222,18 @@ end
     @test Union{Int, Missing}[1] != Union{Int, Missing}[2]
 end
 
+@testset "== and != on tuples" begin
+    @test ismissing((1, missing) == (1, missing))
+    @test ismissing(("a", missing) == ("a", missing))
+    @test ismissing((missing,) == (missing,))
+    @test ismissing((missing, 2) == (1, missing))
+
+    @test ismissing((1, missing) != (1, missing))
+    @test ismissing(("a", missing) != ("a", missing))
+    @test ismissing((missing,) != (missing,))
+    @test ismissing((missing, 2) != (1, missing))
+end
+
 @testset "any & all" begin
     @test any([true, missing])
     @test any(x -> x == 1, [1, missing])