fix: panic when duplicate verbs are found

go-runtime/compile/schema.go

@@ -470,6 +470,13 @@ func visitFuncDecl(pctx *parseContext, node *ast.FuncDecl) (verb *schema.Verb, e
 	if !isVerb {
 		return nil, nil
 	}
+
+	for _, name := range pctx.nativeNames {
+		if name == node.Name.Name {
+			return nil, errorf(node, "verb %q already exported", node.Name.Name)
+		}
+	}
+
 	fnt := pctx.pkg.TypesInfo.Defs[node.Name].(*types.Func) //nolint:forcetypeassert
 	sig := fnt.Type().(*types.Signature)                    //nolint:forcetypeassert
 	if sig.Recv() != nil {

go-runtime/compile/schema_test.go

@@ -241,3 +241,12 @@ func TestErrorReporting(t *testing.T) {
 	_, _, err := ExtractModuleSchema("testdata/failing")
 	assert.EqualError(t, err, filepath.Join(pwd, `testdata/failing/failing.go`)+`:14:2-46: call must have exactly three arguments`)
 }
+
+func TestDuplicateVerbNames(t *testing.T) {
+	if testing.Short() {
+		t.SkipNow()
+	}
+	pwd, _ := os.Getwd()
+	_, _, err := ExtractModuleSchema("testdata/duplicateverbs")
+	assert.EqualError(t, err, filepath.Join(pwd, `testdata/duplicateverbs/duplicateverbs.go`)+`:23:1-2: verb "Time" already exported`)
+}

go-runtime/compile/testdata/duplicateverbs/duplicateverbs.go

@@ -0,0 +1,25 @@
+package duplicateverbs
+
+import (
+	"context"
+	"time"
+)
+
+type TimeRequest struct {
+	Name string
+}
+type TimeResponse struct {
+	Time time.Time
+}
+
+// Time returns the current time.
+//
+//ftl:export
+func Time(ctx context.Context, req TimeRequest) (TimeResponse, error) {
+	return TimeResponse{Time: time.Now()}, nil
+}
+
+//ftl:export
+func Time(ctx context.Context, req TimeRequest) (TimeResponse, error) {
+	return TimeResponse{Time: time.Now()}, nil
+}

go-runtime/compile/testdata/duplicateverbs/ftl.toml

@@ -0,0 +1,2 @@
+module = "duplicateverbs"
+language = "go"

go-runtime/compile/testdata/duplicateverbs/go.mod

@@ -0,0 +1,45 @@
+module ftl/duplicateverbs
+
+go 1.22.1
+
+replace github.com/TBD54566975/ftl => ../../../..
+
+require github.com/TBD54566975/ftl v0.150.3
+
+require (
+	connectrpc.com/connect v1.16.0 // indirect
+	connectrpc.com/grpcreflect v1.2.0 // indirect
+	connectrpc.com/otelconnect v0.7.0 // indirect
+	github.com/BurntSushi/toml v1.3.2 // indirect
+	github.com/TBD54566975/scaffolder v0.8.0 // indirect
+	github.com/alecthomas/concurrency v0.0.2 // indirect
+	github.com/alecthomas/kong v0.9.0 // indirect
+	github.com/alecthomas/participle/v2 v2.1.1 // indirect
+	github.com/alecthomas/types v0.13.0 // indirect
+	github.com/alessio/shellescape v1.4.2 // indirect
+	github.com/danieljoos/wincred v1.2.0 // indirect
+	github.com/go-logr/logr v1.4.1 // indirect
+	github.com/go-logr/stdr v1.2.2 // indirect
+	github.com/godbus/dbus/v5 v5.1.0 // indirect
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20221227161230-091c0ba34f0a // indirect
+	github.com/jackc/pgx/v5 v5.5.5 // indirect
+	github.com/jackc/puddle/v2 v2.2.1 // indirect
+	github.com/jpillora/backoff v1.0.0 // indirect
+	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/swaggest/jsonschema-go v0.3.70 // indirect
+	github.com/swaggest/refl v1.3.0 // indirect
+	github.com/zalando/go-keyring v0.2.4 // indirect
+	go.opentelemetry.io/otel v1.24.0 // indirect
+	go.opentelemetry.io/otel/metric v1.24.0 // indirect
+	go.opentelemetry.io/otel/trace v1.24.0 // indirect
+	golang.org/x/crypto v0.21.0 // indirect
+	golang.org/x/exp v0.0.0-20240222234643-814bf88cf225 // indirect
+	golang.org/x/mod v0.16.0 // indirect
+	golang.org/x/net v0.22.0 // indirect
+	golang.org/x/sync v0.6.0 // indirect
+	golang.org/x/sys v0.18.0 // indirect
+	golang.org/x/text v0.14.0 // indirect
+	google.golang.org/protobuf v1.33.0 // indirect
+)