From 9ce148b1059e4da746a11f1d80a653340216c468 Mon Sep 17 00:00:00 2001
From: Anthony Ramine <n.oxyde@gmail.com>
Date: Mon, 22 Jul 2013 21:41:31 +0200
Subject: Fix unsafe variable tracking in try expressions

Variables used in the body of a try expression were marked as unsafe
*and* used, which makes no sense as an unsafe variable can't be used.

Function vtsubtract/2 is used to forget usage of such unsafe variables.

Reported-by: Paul Davis
---
 lib/stdlib/src/erl_lint.erl        |  2 +-
 lib/stdlib/test/erl_lint_SUITE.erl | 19 ++++++++++++++++++-
 2 files changed, 19 insertions(+), 2 deletions(-)

(limited to 'lib/stdlib')

diff --git a/lib/stdlib/src/erl_lint.erl b/lib/stdlib/src/erl_lint.erl
index 9284f08b30..708ef44fed 100644
--- a/lib/stdlib/src/erl_lint.erl
+++ b/lib/stdlib/src/erl_lint.erl
@@ -2108,7 +2108,7 @@ expr({'try',Line,Es,Scs,Ccs,As}, Vt, St0) ->
     {Evt0,St1} = exprs(Es, Vt, St0),
     TryLine = {'try',Line},
     Uvt = vtunsafe(vtnames(vtnew(Evt0, Vt)), TryLine, []),
-    Evt1 = vtupdate(Uvt, Evt0),
+    Evt1 = vtupdate(Uvt, vtsubtract(Evt0, Uvt)),
     {Sccs,St2} = icrt_clauses(Scs++Ccs, TryLine, vtupdate(Evt1, Vt), St1),
     Rvt0 = Sccs,
     Rvt1 = vtupdate(vtunsafe(vtnames(vtnew(Rvt0, Vt)), TryLine, []), Rvt0),
diff --git a/lib/stdlib/test/erl_lint_SUITE.erl b/lib/stdlib/test/erl_lint_SUITE.erl
index 0bcf9b3e01..a1a9839bae 100644
--- a/lib/stdlib/test/erl_lint_SUITE.erl
+++ b/lib/stdlib/test/erl_lint_SUITE.erl
@@ -1098,7 +1098,24 @@ unsafe_vars_try(Config) when is_list(Config) ->
 		    {10,erl_lint,{unsafe_var,'Ra',{'try',3}}},
 		    {10,erl_lint,{unsafe_var,'Rc',{'try',3}}},
 		    {10,erl_lint,{unsafe_var,'Ro',{'try',3}}}],
-	    []}}],
+	    []}},
+          {unsafe_try5,
+           <<"bang() ->
+                case 1 of
+                  nil ->
+                    Acc = 2;
+                  _ ->
+                    try
+                      Acc = 3,
+                      Acc
+                    catch _:_ ->
+                      ok
+                    end
+                end,
+                Acc.
+           ">>,
+           [],
+           {errors,[{13,erl_lint,{unsafe_var,'Acc',{'try',6}}}],[]}}],
         ?line [] = run(Config, Ts),
     ok.
 
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