Pass through try-compatible errors

try/try.go

@@ -47,7 +47,14 @@ type call struct {
 }
 
 // FromErr wraps a standard error into a try-compatible one with extended stack info.
-func FromErr(err error) *tryErr {
+func FromErr(err error) Err {
+	// If the error is already try-compatible, return
+	//nolint:errorlint
+	cterr, ok := err.(Err)
+	if ok {
+		return cterr
+	}
+
 	terr := &tryErr{err: err, callStack: []call{}}
 
 	pc, _, _, ok := runtime.Caller(0)
@@ -82,7 +89,7 @@ func FromErr(err error) *tryErr {
 }
 
 // NewErr creates a new try-compatible error with extended stack info.
-func NewErr(msg string) *tryErr {
+func NewErr(msg string) Err {
 	return FromErr(errors.New(msg))
 }
 
@@ -179,9 +186,6 @@ func check(args []interface{}) {
 // return errors there is a Catch function. Note! The handler function f is
 // called only when err != nil.
 func Handle(err *Err, f func()) {
-	// This and Catch are similar but we need to call recover() here because
-	// how it works with defer. We cannot refactor these to use same function.
-
 	// We put real panic objects back and keep only those which are
 	// carrying our errors. We must also call all of the handlers in defer
 	// stack.
@@ -208,9 +212,6 @@ func Handle(err *Err, f func()) {
 // Catch function per non error returning function. See Handle for more
 // information.
 func Catch(f func(err Err)) {
-	// This and Handle are similar but we need to call recover here because how
-	// it works with defer. We cannot refactor these 2 to use same function.
-
 	if r := recover(); r != nil {
 		e, ok := r.(Err)
 		if !ok {
@@ -223,9 +224,6 @@ func Catch(f func(err Err)) {
 // CatchAll is a helper function to catch and write handlers for all errors and
 // all panics thrown in the current go routine.
 func CatchAll(errorHandler func(err Err), panicHandler func(v interface{})) {
-	// This and Handle are similar but we need to call recover here because how
-	// it works with defer. We cannot refactor these 2 to use same function.
-
 	if r := recover(); r != nil {
 		e, ok := r.(Err)
 		if ok {
@@ -256,9 +254,6 @@ func CatchTrace(exit int) {
 // their errors. If you want to annotate errors see Annotate for more
 // information.
 func Return(err *Err) {
-	// This and Handle are similar but we need to call recover here because how
-	// it works with defer. We cannot refactor these two to use same function.
-
 	if r := recover(); r != nil {
 		e, ok := r.(Err)
 		if !ok {
@@ -268,13 +263,19 @@ func Return(err *Err) {
 	}
 }
 
-// Annotate is for annotating an error. It's similar to Returnf but it takes only
-// two arguments: a prefix string and a pointer to error. It adds ": " between
-// the prefix and the error text automatically.
-func Annotate(err *Err, msg string) {
-	// This and Handle are similar but we need to call recover here because how
-	// it works with defer. We cannot refactor these two to use same function.
+// ReturnStd is like Return, but it returns the Go standard error type.
+func ReturnStd(err *error) {
+	if r := recover(); r != nil {
+		e, ok := r.(Err)
+		if !ok {
+			panic(r) // Not ours, carry on panicking
+		}
+		*err = e.Unwrap()
+	}
+}
 
+// Annotate adds additional messages to the error.
+func Annotate(err *Err, msg string) {
 	if r := recover(); r != nil {
 		e, ok := r.(Err)
 		if !ok {

try/try_test.go

@@ -206,6 +206,36 @@ func TestErrCompare(t *testing.T) {
 	}
 }
 
+func TestReturnStd(t *testing.T) {
+	tf := func() (err error) {
+		defer ReturnStd(&err)
+		String(throw())
+		return
+	}
+
+	err := tf()
+
+	if err.Error() != "this is an ERROR" {
+		t.Fail()
+	}
+}
+
+func TestCheckTryErr(t *testing.T) {
+	testErr := NewErr("TestErr")
+
+	tf := func() (err Err) {
+		defer Return(&err)
+		Check(testErr)
+		return
+	}
+
+	err := tf()
+
+	if err != testErr {
+		t.Fail()
+	}
+}
+
 func ExampleReturn() {
 	var err Err
 	defer Return(&err)