Added type info in NL error message (#1872)

* Added type info in NL error message

* Fix typo (twice)

* Add tests for errors when using Aff/Quadx in NLexpressions

* Fix typo

src/parse_nlp.jl

@@ -199,11 +199,17 @@ end
 function _parse_NL_expr_runtime(m::Model, x::GenericQuadExpr, tape, parent, values)
     error("Unexpected quadratic expression $x in nonlinear expression. " *
           "Quadratic expressions (e.g., created using @expression) and " *
-          "nonlinear expression cannot be mixed.")
+          "nonlinear expressions cannot be mixed.")
+end
+
+function _parse_NL_expr_runtime(m::Model, x::GenericAffExpr, tape, parent, values)
+    error("Unexpected affine expression $x in nonlinear expression. " *
+          "Affine expressions (e.g., created using @expression) and " *
+          "nonlinear expressions cannot be mixed.")
 end
 
 function _parse_NL_expr_runtime(m::Model, x, tape, parent, values)
-    error("Unexpected object $x in nonlinear expression.")
+    error("Unexpected object $x (of type $(typeof(x)) in nonlinear expression.")
 end
 
 function _expression_complexity(ex::Expr)

test/nlp.jl

@@ -619,4 +619,30 @@
         evaluator = JuMP.NLPEvaluator(model)
         @test !(:Hess in MOI.features_available(evaluator))
     end
+
+    @testset "Error on using AffExpr in NLexpression" begin
+        model = Model()
+        @variable(model, x)
+        @variable(model, y)
+        A = x + y
+        expected_exception = ErrorException(
+            "Unexpected affine expression x + y in nonlinear expression. " *
+            "Affine expressions (e.g., created using @expression) and " *
+            "nonlinear expressions cannot be mixed."
+        )
+        @test_throws expected_exception @NLexpression(model, A)
+    end
+
+    @testset "Error on using QuadExpr in NLexpression" begin
+        model = Model()
+        @variable(model, x)
+        @variable(model, y)
+        A = x*y
+        expected_exception = ErrorException(
+            "Unexpected quadratic expression x*y in nonlinear expression. " *
+            "Quadratic expressions (e.g., created using @expression) and " *
+            "nonlinear expressions cannot be mixed."
+        )
+        @test_throws expected_exception @NLexpression(model, A)
+    end
 end