Update

docs/src/manual/nonlinear.md

@@ -370,7 +370,7 @@ x² - 0.2 x + 0.010000000000000002
 julia> typeof(f)
 QuadExpr (alias for GenericQuadExpr{Float64, GenericVariableRef{Float64}})
 ```
-To over-ride this behavior, use the [`@force_nonlinear`](@ref) macro:
+To override this behavior, use the [`@force_nonlinear`](@ref) macro:
 ```jldoctest force_nonlinear
 julia> g = @force_nonlinear((x - 0.1)^2)
 (x - 0.1) ^ 2

src/macros/@force_nonlinear.jl

@@ -108,11 +108,14 @@ macro force_nonlinear(expr)
         end
         return x
     end
-    return quote
-        r = $(esc(ret))
-        if !(r isa $GenericNonlinearExpr)
-            $error_fn("expression did not produce a GenericNonlinearExpr")
-        end
-        r
-    end
+    return Expr(:call, _force_nonlinear, error_fn, esc(ret))
+end
+
+_force_nonlinear(::F, ret::GenericNonlinearExpr) where {F} = ret
+
+function _force_nonlinear(error_fn::F, ret::Any) where {F}
+    return error_fn(
+        "expression did not produce a `GenericNonlinearExpr`. Got a " *
+        "`$(typeof(ret))`: $(ret)",
+    )
 end

test/test_macros.jl

@@ -2373,7 +2373,7 @@ function test_force_nonlinear()
     @test @force_nonlinear(x^2) isa GenericNonlinearExpr
     @test_throws_runtime(
         ErrorException(
-            "In `@force_nonlinear(x)`: expression did not produce a GenericNonlinearExpr",
+            "In `@force_nonlinear(x)`: expression did not produce a `GenericNonlinearExpr`. Got a `$(typeof(x))`: $x",
         ),
         @force_nonlinear(x),
     )