Allow variables bound in 'try' to be used in 'of' clauses #2662
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The following program would not compile:
-module(foo).
baz() ->
try Bar = 42 of
_ -> Bar
after
ok
end.
The error message is "foo.erl:4: variable 'Bar' unsafe in 'try' (line 3)".
There is no reason for 'Bar' to be unsafe, because if the pattern
after `of` is reached, `Bar = 42` must have been successfully evaluated.
https://bugs.erlang.org/browse/ERL-1281
bjorng
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Jan 12, 2021
In commit 8a9a443 introduced by erlang#2662, a restriction regarding variables in try/catch was lifted, allowing variables bound between `try` and `of` to be used later: baz() -> try Bar = 0 of _ -> Bar after 0 end. (In OTP 23 and earlier that would be a compilation error because `Bar` would be considered unsafe.) The lifted restriction was not properly handled by dialyzer. Attempting to analyze the the following module would crash dialyzer: -module(dialyzer_bug). -export([main/0]). main() -> try A = foo() of _ -> A after ok end. foo() -> 1. https://bugs.erlang.org/browse/ERL-1454
bjorng
added a commit
to bjorng/otp
that referenced
this pull request
Jan 12, 2021
In commit 8a9a443 introduced by erlang#2662, a restriction regarding variables in try/catch was lifted, allowing variables bound between `try` and `of` to be used later: baz() -> try Bar = 0 of _ -> Bar after 0 end. (In OTP 23 and earlier that would be a compilation error because `Bar` would be considered unsafe.) The lifted restriction was not properly handled by dialyzer. Attempting to analyze the the following module would crash dialyzer: -module(dialyzer_bug). -export([main/0]). main() -> try A = foo() of _ -> A after ok end. foo() -> 1. https://bugs.erlang.org/browse/ERL-1454
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The following program would not compile:
The error message is "foo.erl:4: variable 'Bar' unsafe in 'try' (line 3)".
There is no reason for 'Bar' to be unsafe, because if the pattern
after
ofis reached,Bar = 42must have been successfully evaluated.https://bugs.erlang.org/browse/ERL-1281