[erlang-bugs] try in shell

[Daniel Luna]

The answer to your question is called f().

Your variables are bound in all future catch statements and won't match.

The errors from compilation is about the *statement*, not the full
function. The statement will result in an arithmetic error even if the
function won't.

Your third example in the shell leading to the erl_eval:expr/3 result looks
like a bug in the shell though. I'm guessing that the shell strips one
layer of stack trace to show the original function, but this solution leads
to the wrong result when there's an extra level of indirection.

Regards,

Daniel
On Sep 16, 2014 6:18 PM, "Tony Rogvall" <tony@REDACTED> wrote:

> Hi!
>
> Not sure how this is supposed to be, given that there is a shell function
> called catch_exception/1.
>
> Running in 17.1 (approx)
>
> > try throw(x) catch Class:Reason -> {Class,Reason} end.
> {throw,x}
>
> > try exit(2) catch Class:Reason -> {Class,Reason} end.
> * exception exit: 2
>
> > try foo:bar() catch Class:Reason -> {Class,Reason} end.
> * exception error: undefined function erl_eval:expr/3
>
> > try 1/0 catch Class:Reason -> {Class,Reason} end.
> * exception error: an error occurred when evaluating an arithmetic
> expression
>
> > try (a=b) catch Class:Reason -> {Class,Reason} end.
> * exception error: no match of right hand side value b
>
> Putting the above try expression in a module:
>
> -module(tryme).
> -compile(export_all).
>
> test1() ->
>     try throw(x) catch Class:Reason -> {Class,Reason} end.
>
> test2() ->
>     try exit(2) catch Class:Reason -> {Class,Reason} end.
>
> test3() ->
>     try (a=b) catch Class:Reason -> {Class,Reason} end.
>
> test4() ->
>     try 1/0 catch Class:Reason -> {Class,Reason} end.
>
> test5() ->
>     try foo:bar() catch Class:Reason -> {Class,Reason} end.
>
>
> First compile:
> tryme.erl:11: Warning: no clause will ever match
> tryme.erl:14: Warning: this expression will fail with a 'badarith'
> exception
>
> On line 11 there are no try clauses, but catch clauses that will always
> match, so the warning is a bit strange.
> And the expression on line 14 is a try, so it will never fail with
> badarith, possibly return an error tuple lets see:
>
> > tryme:test1().
> {throw,x}
> > tryme:test2().
> {exit,2}
> > tryme:test3().
> {error,{badmatch,b}}
> > tryme:test4().
> {error,badarith}
> > tryme:test5().
> {error,undef}
>
> This looks a bit more like I would expect.
>
> Comments?
>
> /Tony
>
>
>
>
>
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