fix unique over a dimension to use isequal over == (#42737)

(cherry picked from commit 011fda9)

Author: KristofferC

base/multidimensional.jl

@@ -1614,7 +1614,7 @@ _unique_dims(A::AbstractArray, dims::Colon) = invoke(unique, Tuple{Any}, A)
             else
                 j_d = i_d
             end) begin
-                if (@nref $N A j) != (@nref $N A i)
+                if !isequal((@nref $N A j), (@nref $N A i))
                     collided[k] = true
                 end
             end
@@ -1644,7 +1644,7 @@ _unique_dims(A::AbstractArray, dims::Colon) = invoke(unique, Tuple{Any}, A)
                         j_d = i_d
                     end
                 end begin
-                    if (@nref $N A j) != (@nref $N A i)
+                    if !isequal((@nref $N A j), (@nref $N A i))
                         nowcollided[k] = true
                     end
                 end

test/arrayops.jl

@@ -778,6 +778,10 @@ let A, B, C, D
 
     # With hash collisions
     @test map(x -> x.x, unique(map(HashCollision, B), dims=1)) == C
+
+    # With NaNs:
+    E = [1 NaN 3; 1 NaN 3; 1 NaN 3];
+    @test isequal(unique(E, dims=1), [1  NaN  3])
 end
 
 @testset "large matrices transpose" begin