Add long error explanation for E0594

[GuillaumeGomez]

Part of #61137.

r? @Dylan-DPC

[rust-highfive]

Some changes occurred in diagnostic error codes

cc @GuillaumeGomez

[Dylan-DPC-zz]

Suggested change

	To fix this error, just declare `ss` as mutable by using the `mut` keyword:
	To fix this error, declare `ss` as mutable by using the `mut` keyword:

[GuillaumeGomez]

Thanks! I'll update once the error codes have been moved.

[bors]

☔ The latest upstream changes (presumably #66314) made this pull request unmergeable. Please resolve the merge conflicts.

[rust-highfive]

The job x86_64-gnu-llvm-6.0 of your PR failed (pretty log, 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.

2019-11-18T18:04:38.6373339Z ##[command]git remote add origin https://github.com/rust-lang/rust
2019-11-18T18:04:38.6578076Z ##[command]git config gc.auto 0
2019-11-18T18:04:38.6657108Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2019-11-18T18:04:38.6721902Z ##[command]git config --get-all http.proxy
2019-11-18T18:04:39.3179459Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/66155/merge:refs/remotes/pull/66155/merge
---
2019-11-18T18:11:04.2161013Z    Compiling serde_json v1.0.40
2019-11-18T18:11:06.0701168Z    Compiling tidy v0.1.0 (/checkout/src/tools/tidy)
2019-11-18T18:11:17.7628291Z     Finished release [optimized] target(s) in 1m 31s
2019-11-18T18:11:17.7721260Z tidy check
2019-11-18T18:11:19.2419733Z tidy error: duplicate error code: 593
2019-11-18T18:11:19.2420589Z tidy error: /checkout/src/librustc_error_codes/error_codes.rs:320: E0593: include_str!("./error_codes/E0593.md"),
2019-11-18T18:11:19.2420977Z tidy error: /checkout/src/librustc_error_codes/error_codes.rs:321: E0593: include_str!("./error_codes/E0594.md"),
2019-11-18T18:11:20.6674390Z some tidy checks failed
2019-11-18T18:11:20.6674468Z Found 441 error codes
2019-11-18T18:11:20.6674550Z Found 0 error codes with no tests
2019-11-18T18:11:20.6674621Z Done!
2019-11-18T18:11:20.6674621Z Done!
2019-11-18T18:11:20.6674653Z 
2019-11-18T18:11:20.6674680Z 
2019-11-18T18:11:20.6675543Z command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/tidy" "/checkout/src" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "--no-vendor"
2019-11-18T18:11:20.6675646Z 
2019-11-18T18:11:20.6675692Z 
2019-11-18T18:11:20.6678693Z failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
2019-11-18T18:11:20.6678998Z Build completed unsuccessfully in 0:01:35
2019-11-18T18:11:20.6678998Z Build completed unsuccessfully in 0:01:35
2019-11-18T18:11:20.6732323Z == clock drift check ==
2019-11-18T18:11:20.6744182Z   local time: Mon Nov 18 18:11:20 UTC 2019
2019-11-18T18:11:20.9508226Z   network time: Mon, 18 Nov 2019 18:11:20 GMT
2019-11-18T18:11:20.9508918Z == end clock drift check ==
2019-11-18T18:11:22.3187591Z 
2019-11-18T18:11:22.3304308Z ##[error]Bash exited with code '1'.
2019-11-18T18:11:22.3353973Z ##[section]Starting: Checkout
2019-11-18T18:11:22.3355644Z ==============================================================================
2019-11-18T18:11:22.3355702Z Task         : Get sources
2019-11-18T18:11:22.3355766Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.

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)

[Dylan-DPC-zz]

And the ferris wheel continues to roll 🎡

@bors r+ rollup

[bors]

📌 Commit c981c99 has been approved by Dylan-DPC