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Fail typecheck if we encounter a bogus break #51070

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merged 1 commit into from
May 26, 2018

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@est31 est31 commented May 26, 2018

Lone breaks outside of loops create errors in the
loop check pass but as they are not fatal,
compilation continues.

MIR building code assumes all HIR break statements
to point to valid locations and fires ICEs if this
assumption is violated. In normal compilation,
this causes no issues, as code apparently prevents
MIR from being built if errors are present.

However, before that, typecheck runs and with it
MIR const eval. Here we operate differently
from normal compilation: it doesn't check for any
errors except for type checker ones and then
directly builds the MIR.

This constellation causes an ICE-on-error if
bogus break statements are being put into array
length expressions.

This commit fixes this ICE by letting typecheck
fail if bogus break statements are encountered.
This way, MIR const eval fails cleanly with a
type check error.

Fixes #50576
Fixes #50581

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r? @estebank

(rust_highfive has picked a reviewer for you, use r? to override)

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 26, 2018
@est31
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est31 commented May 26, 2018

r? @oli-obk

@rust-highfive rust-highfive assigned oli-obk and unassigned estebank May 26, 2018
Lone breaks outside of loops create errors in the
loop check pass but as they are not fatal,
compilation continues.

MIR building code assumes all HIR break statements
to point to valid locations and fires ICEs if this
assumption is violated. In normal compilation,
this causes no issues, as code apparently prevents
MIR from being built if errors are present.

However, before that, typecheck runs and with it
MIR const eval. Here we operate differently
from normal compilation: it doesn't check for any
errors except for type checker ones and then
directly builds the MIR.

This constellation causes an ICE-on-error if
bogus break statements are being put into array
length expressions.

This commit fixes this ICE by letting typecheck
fail if bogus break statements are encountered.
This way, MIR const eval fails cleanly with a
type check error.

Fixes rust-lang#50576
Fixes rust-lang#50581
@estebank
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@bors r+ rollup

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bors commented May 26, 2018

📌 Commit 5724dad has been approved by estebank

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels May 26, 2018
kennytm added a commit to kennytm/rust that referenced this pull request May 26, 2018
Fail typecheck if we encounter a bogus break

Lone breaks outside of loops create errors in the
loop check pass but as they are not fatal,
compilation continues.

MIR building code assumes all HIR break statements
to point to valid locations and fires ICEs if this
assumption is violated. In normal compilation,
this causes no issues, as code apparently prevents
MIR from being built if errors are present.

However, before that, typecheck runs and with it
MIR const eval. Here we operate differently
from normal compilation: it doesn't check for any
errors except for type checker ones and then
directly builds the MIR.

This constellation causes an ICE-on-error if
bogus break statements are being put into array
length expressions.

This commit fixes this ICE by letting typecheck
fail if bogus break statements are encountered.
This way, MIR const eval fails cleanly with a
type check error.

Fixes rust-lang#50576
Fixes rust-lang#50581
bors added a commit that referenced this pull request May 26, 2018
Rollup of 11 pull requests

Successful merges:

 - #50987 (Underline multiple suggested replacements in the same line)
 - #51014 (Add documentation about env! second argument)
 - #51034 (Remove unused lowering field and method)
 - #51047 (Use AllFacts from polonius-engine)
 - #51048 (Add more missing examples for Formatter)
 - #51056 (Mention and use `Once::new` instead of `ONCE_INIT`)
 - #51059 (What does an expression look like, that consists only of special characters?)
 - #51065 (Update nomicon link in transmute docs)
 - #51067 (Add inner links in documentation)
 - #51070 (Fail typecheck if we encounter a bogus break)
 - #51073 (Rename TokenStream::empty to TokenStream::new)

Failed merges:
@bors bors merged commit 5724dad into rust-lang:master May 26, 2018
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