add map key validation

go-runtime/ftl/ftltest/fake.go

@@ -2,7 +2,9 @@ package ftltest
 
 import (
 	"context"
+	"fmt"
 	"reflect"
+	"strings"
 
 	"github.com/TBD54566975/ftl/go-runtime/internal"
 	"github.com/TBD54566975/ftl/internal/modulecontext"
@@ -31,12 +33,12 @@ func (f *fakeFTL) PublishEvent(ctx context.Context, topic string, event any) err
 }
 
 func (f *fakeFTL) addMapMock(ctx context.Context, mapper any, mockMap func(context.Context) (any, error)) {
-	key := reflect.ValueOf(mapper).Pointer()
+	key := makeMapKey(mapper)
 	f.mockMaps[key] = mockMap
 }
 
 func (f *fakeFTL) CallMap(ctx context.Context, mapper any, mapImpl func(context.Context) (any, error)) any {
-	key := reflect.ValueOf(mapper).Pointer()
+	key := makeMapKey(mapper)
 	mockMap, ok := f.mockMaps[key]
 	if ok {
 		return actuallyCallMap(ctx, mockMap)
@@ -48,6 +50,18 @@ func (f *fakeFTL) CallMap(ctx context.Context, mapper any, mapImpl func(context.
 	return nil
 }
 
+func makeMapKey(mapper any) uintptr {
+	v := reflect.ValueOf(mapper)
+	if v.Kind() != reflect.Pointer {
+		panic("fakeFTL received object that was not a pointer, expected *MapHandle")
+	}
+	underlying := v.Elem().Type().Name()
+	if !strings.HasPrefix(underlying, "MapHandle[") {
+		panic(fmt.Sprintf("fakeFTL received *%s, expected *MapHandle", underlying))
+	}
+	return v.Pointer()
+}
+
 func actuallyCallMap(ctx context.Context, impl modulecontext.Map) any {
 	out, err := impl(ctx)
 	if err != nil {

go-runtime/ftl/testdata/go/mapper/mapper_test.go

@@ -8,7 +8,7 @@ import (
 	"github.com/alecthomas/assert/v2"
 )
 
-/*func TestGet(t *testing.T) {
+func TestGet(t *testing.T) {
 	ctx := ftltest.Context(ftltest.WithMapsAllowed())
 	got := m.Get(ctx)
 	assert.Equal(t, got, 9)
@@ -19,7 +19,7 @@ func TestPanicsWithoutExplicitlyAllowingMaps(t *testing.T) {
 	assert.Panics(t, func() {
 		m.Get(ctx)
 	})
-        }*/
+}
 
 func TestMockGet(t *testing.T) {
 	mockOut := 123