Stop compilation on missing const_generics feature.

[lcnr]

fixes #69913

Currently aborts right after parsing. Considering that most problems only start during type checking,
this is not optimal.

I do not know of a simple way to delay this abort.

r? @varkor
cc @eddyb

[varkor]

After lazy normalisation (#67890) is merged, we should be able to remove this, but this is probably better than ICEing for now.

[rust-highfive]

The job mingw-check 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.

2020-03-18T23:10:18.5707966Z ========================== Starting Command Output ===========================
2020-03-18T23:10:18.5711078Z [command]/bin/bash --noprofile --norc /home/vsts/work/_temp/39878a8c-65cf-4950-92a9-fa856c5a37ef.sh
2020-03-18T23:10:18.5711488Z 
2020-03-18T23:10:18.5716138Z ##[section]Finishing: Disable git automatic line ending conversion
2020-03-18T23:10:18.5735399Z ##[section]Starting: Checkout rust-lang/rust@refs/pull/70122/merge to s
2020-03-18T23:10:18.5738748Z Task         : Get sources
2020-03-18T23:10:18.5739067Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
2020-03-18T23:10:18.5739376Z Version      : 1.0.0
2020-03-18T23:10:18.5739579Z Author       : Microsoft
---
2020-03-18T23:10:19.5612796Z ##[command]git remote add origin https://github.com/rust-lang/rust
2020-03-18T23:10:19.5618137Z ##[command]git config gc.auto 0
2020-03-18T23:10:19.5621703Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2020-03-18T23:10:19.5624993Z ##[command]git config --get-all http.proxy
2020-03-18T23:10:19.5631287Z ##[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/70122/merge:refs/remotes/pull/70122/merge
---
2020-03-18T23:19:13.8461779Z configure: build.locked-deps    := True
2020-03-18T23:19:13.8462229Z configure: llvm.ccache          := sccache
2020-03-18T23:19:13.8462844Z configure: build.cargo-native-static := True
2020-03-18T23:19:13.8463441Z configure: dist.missing-tools   := True
2020-03-18T23:19:13.8464170Z configure: build.configure-args := ['--enable-sccache', '--disable-manage-submodu ...
2020-03-18T23:19:13.8464965Z configure: writing `config.toml` in current directory
2020-03-18T23:19:13.8465327Z configure: 
2020-03-18T23:19:13.8465853Z configure: run `python /checkout/x.py --help`
2020-03-18T23:19:13.8508419Z configure: 
---
2020-03-18T23:26:34.2356852Z     Finished release [optimized] target(s) in 8.66s
2020-03-18T23:26:34.2462044Z tidy check
2020-03-18T23:26:39.9038822Z * 591 error codes
2020-03-18T23:26:39.9039158Z * highest error code: E0748
2020-03-18T23:26:40.2572115Z tidy error: Found 1 features without a gate test.
2020-03-18T23:26:40.2573431Z Expected a gate test for the feature 'const_generics'.
2020-03-18T23:26:40.2574192Z Hint: create a failing test file named 'feature-gate-const_generics.rs'
2020-03-18T23:26:40.2574857Z       in the 'ui' test suite, with its failures due to
2020-03-18T23:26:40.2575310Z       missing usage of `#![feature(const_generics)]`.
2020-03-18T23:26:40.2575985Z Hint: If you already have such a test and don't want to rename it,
2020-03-18T23:26:40.2576690Z       you can also add a // gate-test-const_generics line to the test file.
2020-03-18T23:26:41.1660359Z Found 489 error codes
2020-03-18T23:26:41.1660664Z Found 0 error codes with no tests
2020-03-18T23:26:41.1660849Z Done!
2020-03-18T23:26:41.1661014Z some tidy checks failed
2020-03-18T23:26:41.1661014Z some tidy checks failed
2020-03-18T23:26:41.1661171Z 
2020-03-18T23:26:41.1661269Z 
2020-03-18T23:26:41.1663445Z 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"
2020-03-18T23:26:41.1666061Z 
2020-03-18T23:26:41.1666160Z 
2020-03-18T23:26:41.1666491Z failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
2020-03-18T23:26:41.1667250Z Build completed unsuccessfully in 0:00:26
2020-03-18T23:26:41.1667250Z Build completed unsuccessfully in 0:00:26
2020-03-18T23:26:41.1720381Z == clock drift check ==
2020-03-18T23:26:41.1734207Z   local time: Wed Mar 18 23:26:41 UTC 2020
2020-03-18T23:26:41.4618997Z   network time: Wed, 18 Mar 2020 23:26:41 GMT
2020-03-18T23:26:41.4624199Z == end clock drift check ==
2020-03-18T23:26:41.9528400Z 
2020-03-18T23:26:41.9599441Z ##[error]Bash exited with code '1'.
2020-03-18T23:26:41.9614627Z ##[section]Finishing: Run build
2020-03-18T23:26:41.9662549Z ##[section]Starting: Checkout rust-lang/rust@refs/pull/70122/merge to s
2020-03-18T23:26:41.9668209Z Task         : Get sources
2020-03-18T23:26:41.9668562Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
2020-03-18T23:26:41.9668896Z Version      : 1.0.0
2020-03-18T23:26:41.9669131Z Author       : Microsoft
2020-03-18T23:26:41.9669131Z Author       : Microsoft
2020-03-18T23:26:41.9669492Z Help         : [More Information](https://go.microsoft.com/fwlink/?LinkId=798199)
2020-03-18T23:26:41.9669915Z ==============================================================================
2020-03-18T23:26:42.2995085Z Cleaning any cached credential from repository: rust-lang/rust (GitHub)
2020-03-18T23:26:42.3042371Z ##[section]Finishing: Checkout rust-lang/rust@refs/pull/70122/merge to s
2020-03-18T23:26:42.3131658Z Cleaning up task key
2020-03-18T23:26:42.3133069Z Start cleaning up orphan processes.
2020-03-18T23:26:42.3310319Z Terminate orphan process: pid (4408) (python)
2020-03-18T23:26:42.3573343Z ##[section]Finishing: Finalize Job

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 @rust-lang/infra. (Feature Requests)

[petrochenkov]

I disagree with this change.
There's no point in silencing an ICE on stable channel specifically.
#![feature] attributes are not supposed to have any effect on compilation besides removing the feature gate error.

[rust-highfive]

The job x86_64-gnu-llvm-7 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.

2020-03-19T09:53:36.0003917Z ========================== Starting Command Output ===========================
2020-03-19T09:53:36.0009234Z [command]/bin/bash --noprofile --norc /home/vsts/work/_temp/e109ca65-1b9a-4e92-988e-5a32d42787c2.sh
2020-03-19T09:53:36.0009776Z 
2020-03-19T09:53:36.0015338Z ##[section]Finishing: Disable git automatic line ending conversion
2020-03-19T09:53:36.0036077Z ##[section]Starting: Checkout rust-lang/rust@refs/pull/70122/merge to s
2020-03-19T09:53:36.0039835Z Task         : Get sources
2020-03-19T09:53:36.0040183Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
2020-03-19T09:53:36.0040499Z Version      : 1.0.0
2020-03-19T09:53:36.0040717Z Author       : Microsoft
---
2020-03-19T09:53:37.1359823Z ##[command]git remote add origin https://github.com/rust-lang/rust
2020-03-19T09:53:37.1380264Z ##[command]git config gc.auto 0
2020-03-19T09:53:37.1385490Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2020-03-19T09:53:37.1389323Z ##[command]git config --get-all http.proxy
2020-03-19T09:53:37.1398246Z ##[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/70122/merge:refs/remotes/pull/70122/merge
---
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---
2020-03-19T11:05:10.4313531Z 1 error[E0658]: const generics are unstable
2020-03-19T11:05:10.4314348Z -   --> $DIR/feature-gate-const_generics-fn.rs:1:14
2020-03-19T11:05:10.4315225Z +   --> $DIR/feature-gate-const_generics-fn.rs:3:14
2020-03-19T11:05:10.4315724Z 3    |
2020-03-19T11:05:10.4316145Z 4 LL | fn foo<const X: ()>() {}
2020-03-19T11:05:10.4317001Z 
2020-03-19T11:05:10.4317421Z 
2020-03-19T11:05:10.4317833Z The actual stderr differed from the expected stderr.
2020-03-19T11:05:10.4317833Z The actual stderr differed from the expected stderr.
2020-03-19T11:05:10.4318898Z Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/feature-gates/feature-gate-const_generics-fn/feature-gate-const_generics-fn.stderr
2020-03-19T11:05:10.4322829Z To update references, rerun the tests and pass the `--bless` flag
2020-03-19T11:05:10.4323619Z To only update this specific test, also pass `--test-args feature-gates/feature-gate-const_generics-fn.rs`
2020-03-19T11:05:10.4324114Z error: 1 errors occurred comparing output.
2020-03-19T11:05:10.4324351Z status: exit code: 1
2020-03-19T11:05:10.4324351Z status: exit code: 1
2020-03-19T11:05:10.4326503Z command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/feature-gates/feature-gate-const_generics-fn.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/feature-gates/feature-gate-const_generics-fn" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-A" "unused" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/feature-gates/feature-gate-const_generics-fn/auxiliary"
2020-03-19T11:05:10.4331266Z ------------------------------------------
2020-03-19T11:05:10.4331448Z 
2020-03-19T11:05:10.4331828Z ------------------------------------------
2020-03-19T11:05:10.4332066Z stderr:
2020-03-19T11:05:10.4332066Z stderr:
2020-03-19T11:05:10.4332453Z ------------------------------------------
2020-03-19T11:05:10.4332721Z error[E0658]: const generics are unstable
2020-03-19T11:05:10.4333317Z   --> /checkout/src/test/ui/feature-gates/feature-gate-const_generics-fn.rs:3:14
2020-03-19T11:05:10.4333600Z    |
2020-03-19T11:05:10.4333850Z LL | fn foo<const X: ()>() {} //~ ERROR const generics are unstable
2020-03-19T11:05:10.4334295Z    |
2020-03-19T11:05:10.4334295Z    |
2020-03-19T11:05:10.4334957Z    = note: see issue #44580 <***/issues/44580> for more information
2020-03-19T11:05:10.4336927Z    = help: add `#![feature(const_generics)]` to the crate attributes to enable
2020-03-19T11:05:10.4337357Z error: aborting due to previous error
2020-03-19T11:05:10.4337543Z 
2020-03-19T11:05:10.4338104Z For more information about this error, try `rustc --explain E0658`.
2020-03-19T11:05:10.4338323Z 
---
2020-03-19T11:05:10.4340921Z 1 error[E0658]: const generics are unstable
2020-03-19T11:05:10.4342762Z -   --> $DIR/feature-gate-const_generics-struct.rs:1:18
2020-03-19T11:05:10.4343384Z +   --> $DIR/feature-gate-const_generics-struct.rs:3:18
2020-03-19T11:05:10.4343629Z 3    |
2020-03-19T11:05:10.4344003Z 4 LL | struct Foo<const X: usize>([(); X]);
2020-03-19T11:05:10.4344420Z 
2020-03-19T11:05:10.4344516Z 
2020-03-19T11:05:10.4344719Z The actual stderr differed from the expected stderr.
2020-03-19T11:05:10.4344719Z The actual stderr differed from the expected stderr.
2020-03-19T11:05:10.4345577Z Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/feature-gates/feature-gate-const_generics-struct/feature-gate-const_generics-struct.stderr
2020-03-19T11:05:10.4346324Z To update references, rerun the tests and pass the `--bless` flag
2020-03-19T11:05:10.4346996Z To only update this specific test, also pass `--test-args feature-gates/feature-gate-const_generics-struct.rs`
2020-03-19T11:05:10.4347491Z error: 1 errors occurred comparing output.
2020-03-19T11:05:10.4347725Z status: exit code: 1
2020-03-19T11:05:10.4347725Z status: exit code: 1
2020-03-19T11:05:10.4349887Z command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/feature-gates/feature-gate-const_generics-struct.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/feature-gates/feature-gate-const_generics-struct" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-A" "unused" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/feature-gates/feature-gate-const_generics-struct/auxiliary"
2020-03-19T11:05:10.4351632Z ------------------------------------------
2020-03-19T11:05:10.4351807Z 
2020-03-19T11:05:10.4352299Z ------------------------------------------
2020-03-19T11:05:10.4352509Z stderr:
2020-03-19T11:05:10.4352509Z stderr:
2020-03-19T11:05:10.4352874Z ------------------------------------------
2020-03-19T11:05:10.4353132Z error[E0658]: const generics are unstable
2020-03-19T11:05:10.4353714Z   --> /checkout/src/test/ui/feature-gates/feature-gate-const_generics-struct.rs:3:18
2020-03-19T11:05:10.4353996Z    |
2020-03-19T11:05:10.4354260Z LL | struct Foo<const X: usize>([(); X]); //~ ERROR const generics are unstable
2020-03-19T11:05:10.4354719Z    |
2020-03-19T11:05:10.4354719Z    |
2020-03-19T11:05:10.4355285Z    = note: see issue #44580 <***/issues/44580> for more information
2020-03-19T11:05:10.4355674Z    = help: add `#![feature(const_generics)]` to the crate attributes to enable
2020-03-19T11:05:10.4356084Z error: aborting due to previous error
2020-03-19T11:05:10.4356241Z 
2020-03-19T11:05:10.4356698Z For more information about this error, try `rustc --explain E0658`.
2020-03-19T11:05:10.4357030Z 
---
2020-03-19T11:05:10.4360483Z thread 'main' panicked at 'Some tests failed', src/tools/compiletest/src/main.rs:348:22
2020-03-19T11:05:10.4361014Z note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
2020-03-19T11:05:10.4361377Z 
2020-03-19T11:05:10.4361485Z 
2020-03-19T11:05:10.4365243Z command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--src-base" "/checkout/src/test/ui" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--mode" "ui" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/usr/lib/llvm-7/bin/FileCheck" "--nodejs" "/usr/bin/node" "--host-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--docck-python" "/usr/bin/python2.7" "--lldb-python" "/usr/bin/python2.7" "--gdb" "/usr/bin/gdb" "--quiet" "--llvm-version" "7.0.0\n" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"
2020-03-19T11:05:10.4368010Z 
2020-03-19T11:05:10.4368107Z 
2020-03-19T11:05:10.4368662Z failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test --exclude src/tools/tidy
2020-03-19T11:05:10.4369053Z Build completed unsuccessfully in 1:06:37
2020-03-19T11:05:10.4369053Z Build completed unsuccessfully in 1:06:37
2020-03-19T11:05:10.4400730Z == clock drift check ==
2020-03-19T11:05:10.4418846Z   local time: Thu Mar 19 11:05:10 UTC 2020
2020-03-19T11:05:10.6096603Z   network time: Thu, 19 Mar 2020 11:05:10 GMT
2020-03-19T11:05:10.6099330Z == end clock drift check ==
2020-03-19T11:05:11.0575871Z 
2020-03-19T11:05:11.0682299Z ##[error]Bash exited with code '1'.
2020-03-19T11:05:11.0698847Z ##[section]Finishing: Run build
2020-03-19T11:05:11.0754144Z ##[section]Starting: Checkout rust-lang/rust@refs/pull/70122/merge to s
2020-03-19T11:05:11.0759620Z Task         : Get sources
2020-03-19T11:05:11.0759996Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
2020-03-19T11:05:11.0760322Z Version      : 1.0.0
2020-03-19T11:05:11.0760877Z Author       : Microsoft
2020-03-19T11:05:11.0760877Z Author       : Microsoft
2020-03-19T11:05:11.0761277Z Help         : [More Information](https://go.microsoft.com/fwlink/?LinkId=798199)
2020-03-19T11:05:11.0761687Z ==============================================================================
2020-03-19T11:05:11.4621705Z Cleaning any cached credential from repository: rust-lang/rust (GitHub)
2020-03-19T11:05:11.4676163Z ##[section]Finishing: Checkout rust-lang/rust@refs/pull/70122/merge to s
2020-03-19T11:05:11.4771193Z Cleaning up task key
2020-03-19T11:05:11.4772479Z Start cleaning up orphan processes.
2020-03-19T11:05:11.5088889Z Terminate orphan process: pid (3711) (python)
2020-03-19T11:05:11.5149154Z ##[section]Finishing: Finalize Job

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 @rust-lang/infra. (Feature Requests)

[varkor]

Maybe we should just leave #69913 open until lazy normalisation is merged, in light of @petrochenkov's objection. An ICE isn't pleasant for a user, but they still get a detailed error message beforehand, so it shouldn't be obstructive to them.

[varkor]

Thanks for filing the pull request, though!