Fix the use of closures within #[panic_implementation]

[varkor]

Fixes#51365.

[rust-highfive]

r? @petrochenkov

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[Mark-Simulacrum]

r? @eddyb

[eddyb]

@bors r+

[bors]

📌 Commit f375577 has been approved by eddyb

[bors]

⌛ Testing commit f375577 with merge e70583259c5440970732a36a37a52c0ed5727bf6...

[bors]

💔 Test failed - status-travis

[rust-highfive]

The job x86_64-gnu-aux of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

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############################################################### 87.9%
######################################################################## 100.0%
[00:10:05] extracting /checkout/obj/build/cache/2018-05-10/cargo-beta-x86_64-unknown-linux-gnu.tar.gz
[00:10:05] Updating registry `https://github.com/rust-lang/crates.io-index`
No output has been received in the last 30m0s, this potentially indicates a stalled build or something wrong with the build itself.
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The build has been terminated

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[rust-highfive]

The job x86_64-gnu-aux of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

############################################################### 87.9%
######################################################################## 100.0%
[00:10:05] extracting /checkout/obj/build/cache/2018-05-10/cargo-beta-x86_64-unknown-linux-gnu.tar.gz
[00:10:05] Updating registry `https://github.com/rust-lang/crates.io-index`
No output has been received in the last 30m0s, this potentially indicates a stalled build or something wrong with the build itself.
Check the details on how to adjust your build configuration on: https://docs.travis-ci.com/user/common-build-problems/#Build-times-out-because-no-output-was-received
The build has been terminated

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[Mark-Simulacrum]

@bors retry - network failure