Fix addition/substraction between variable and complex number (#2890)

Author: blegat

src/operators.jl

@@ -30,10 +30,12 @@ _float(J::UniformScaling) = _float(J.λ)
 # _Constant--_Constant obviously already taken care of!
 # _Constant--VariableRef
 function Base.:+(lhs::_Constant, rhs::AbstractVariableRef)
-    return _build_aff_expr(_float(lhs), 1.0, rhs)
+    constant = _float(lhs)
+    return _build_aff_expr(constant, one(constant), rhs)
 end
 function Base.:-(lhs::_Constant, rhs::AbstractVariableRef)
-    return _build_aff_expr(_float(lhs), -1.0, rhs)
+    constant = _float(lhs)
+    return _build_aff_expr(constant, -one(constant), rhs)
 end
 function Base.:*(lhs::_Constant, rhs::AbstractVariableRef)
     if iszero(lhs)

test/complex.jl

@@ -22,6 +22,24 @@ function test_complex_aff_expr()
     return
 end
 
+function test_complex_plus_variable()
+    model = Model()
+    @variable(model, x)
+    y = x + im
+    @test typeof(y) == GenericAffExpr{Complex{Float64},VariableRef}
+    @test y == im + x
+    return
+end
+
+function test_complex_minus_variable()
+    model = Model()
+    @variable(model, x)
+    y = im - x
+    @test typeof(y) == GenericAffExpr{Complex{Float64},VariableRef}
+    @test -y == x - im
+    return
+end
+
 function test_complex_aff_expr_convert()
     model = Model()
     @variable(model, x)