8000 Heisen-variables (2) · Issue #6516 · erlang/otp · GitHub
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Heisen-variables (2) #6516

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ilya-klyuchnikov opened this issue Nov 25, 2022 · 1 comment · Fixed by #6415
Closed

Heisen-variables (2) #6516

ilya-klyuchnikov opened this issue Nov 25, 2022 · 1 comment · Fixed by #6415
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@bjorng
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bug Issue is reported as a bug team:VM Assigned to OTP team VM
Milestone
OTP-26.0

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@ilya-klyuchnikov
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ilya-klyuchnikov commented Nov 25, 2022 •
edited
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(A continuation of #6141)

Describe the bug
Scoping of variables (and whether a variable is already bound or not) is not stable

To Reproduce

-module(scopes).
-compile([export_all, nowarn_export_all]).

scope1() ->
  {
    (X = 4),
    (X = 3)
  }.

scope2() ->
  {
    X = 4,
    (_ = (X = 3))
  }.
$ erlc scopes.erl
scopes.erl:7:6: Warning: no clause will ever match
%    7|     (X = 3)
%     |      ^

scopes.erl:7:6: Warning: this clause cannot match because its guard evaluates to 'false'
%    7|     (X = 3)
%     |      ^


$ erl 
1> scopes:scope1().
** exception error: no match of right hand side value 3
     in function  scopes:scope1/0 (scopes.erl, line 7)
2> scopes:scope2().
{4,3}

Expected behavior
The same behavior for scope1 and scope2. It seems that X is scoped differently under the hood in the 2 functions.

Affected versions
25.1
@ilya-klyuchnikov ilya-klyuchnikov added the bug Issue is reported as a bug label Nov 25, 2022
@bjorng bjorng self-assigned this Nov 26, 2022
@IngelaAndin IngelaAndin added the team:VM Assigned to OTP team VM label Nov 28, 2022
@bjorng bjorng linked a pull request Dec 5, 2022 that will close this issue
Lift restrictions for matching of binaries and maps #6415
Merged
@bjorng bjorng added this to the OTP-26.0 milestone Dec 5, 2022
@bjorng
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bjorng commented Dec 5, 2022

It turns out that this bug is fixed in #6415. We don't plan to fix it in OTP 25.x.

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@bjorng bjorng

Labels
bug Issue is reported as a bug team:VM Assigned to OTP team VM
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Milestone
OTP-26.0
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Lift restrictions for matching of binaries and maps bjorng/otp
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@bjorng @ilya-klyuchnikov @IngelaAndin
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