Fix comparison of ScalarFunctionConstantNotZero (#2190)

Co-authored-by: Benoît Legat <[email protected]>

Author: odow

src/constraints.jl

@@ -73,6 +73,13 @@ struct ScalarFunctionConstantNotZero{T,F,S} <: Exception
     constant::T
 end
 
+function Base.:(==)(
+    x::ScalarFunctionConstantNotZero{T,F,S},
+    y::ScalarFunctionConstantNotZero{T,F,S},
+) where {T,F,S}
+    return x.constant == y.constant
+end
+
 function Base.showerror(
     io::IO,
     err::ScalarFunctionConstantNotZero{T,F,S},

test/errors.jl

@@ -352,6 +352,20 @@ function test_unsupported_nonlinear_operator()
     return
 end
 
+function test_ScalarFunctionConstantNotZero_equality()
+    for T in (Int, Float64, BigFloat)
+        F, S = MOI.ScalarAffineFunction{T}, MOI.EqualTo{T}
+        w = MOI.ScalarFunctionConstantNotZero{T,F,MOI.LessThan{T}}(zero(T))
+        x = MOI.ScalarFunctionConstantNotZero{T,F,S}(zero(T))
+        y = MOI.ScalarFunctionConstantNotZero{T,F,S}(zero(T))
+        z = MOI.ScalarFunctionConstantNotZero{T,F,S}(one(T))
+        @test x == y
+        @test x != z
+        @test w != x
+    end
+    return
+end
+
 function runtests()
     for name in names(@__MODULE__; all = true)
         if startswith("$name", "test_")