Fix incorrect pattern warning "unreachable pattern" #70413

AminArria · 2020-03-25T23:43:28Z

Added is_under_guard parameter to _match::is_useful and only add it to the matrix if false

Tested with:

#![feature(or_patterns)]
fn main() {
    match (3,42) {
        (a,_) | (_,a) if a > 10 => {println!("{}", a)}
        _ => ()
    }

    match Some((3,42)) {
        Some((a, _)) | Some((_, a)) if a > 10 => {println!("{}", a)}
        _ => ()
    
    }

    match Some((3,42)) {
        Some((a, _) | (_, a)) if a > 10 => {println!("{}", a)}
        _ => ()
    }
}

rust-highfive · 2020-03-25T23:43:31Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @estebank (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

Centril

Looks good. :)

Please also add the test cases mentioned in the OP in src/test/ui/or-patterns/issue-70413-no-unreachable-pat-and-guard.rs, with #![deny(unreachable_patterns)] and write // check-pass at the top of the file. Also make sure to ./x.py test --stage 1 --bless --pass check src/test/ui to adjust the fallout in UI tests (see also https://rustc-dev-guide.rust-lang.org/tests/adding.html).

You'll also need to run ./x.py fmt to pacify the rustfmt checks in CI.

Centril · 2020-03-25T23:52:19Z

src/librustc_mir_build/hair/pattern/check_match.rs

@@ -410,7 +410,7 @@ fn check_not_useful<'p, 'tcx>(
 ) -> Result<(), Vec<super::Pat<'tcx>>> {
    let wild_pattern = cx.pattern_arena.alloc(super::Pat::wildcard_from_ty(ty));
    let v = PatStack::from_pattern(wild_pattern);
-    match is_useful(cx, matrix, &v, ConstructWitness, hir_id, true) {


Can you leave a note re. the false in this case?

Added in 4b1aa9fa

Centril · 2020-03-25T23:58:52Z

r? @varkor
cc @Nadrieril

Centril · 2020-03-26T00:31:43Z

src/librustc_mir_build/hair/pattern/_match.rs

@@ -1664,7 +1669,9 @@ crate fn is_useful<'p, 'tcx>(
                    bug!("Encountered or-pat in `v` during exhaustiveness checking")
                }
            }
-            matrix.push(v);
+            if !is_under_guard {


Maybe add a comment here as well re. the purpose of this check.

Added in 4b1aa9fa

rust-highfive · 2020-03-26T01:43:15Z

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2020-03-25T23:44:53.9275302Z ========================== Starting Command Output ===========================
2020-03-25T23:44:53.9278194Z [command]/bin/bash --noprofile --norc /home/vsts/work/_temp/43a298fa-30ed-4420-a21d-4c6ab9484e7c.sh
2020-03-25T23:44:53.9278507Z 
2020-03-25T23:44:53.9282777Z ##[section]Finishing: Disable git automatic line ending conversion
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2020-03-25T23:44:53.9307692Z Version      : 1.0.0
2020-03-25T23:44:53.9307903Z Author       : Microsoft
---
2020-03-25T23:44:54.9230413Z ##[command]git remote add origin https://github.com/rust-lang/rust
2020-03-25T23:44:54.9236632Z ##[command]git config gc.auto 0
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2020-03-25T23:44:54.9246290Z ##[command]git config --get-all http.proxy
2020-03-25T23:44:54.9254381Z ##[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/70413/merge:refs/remotes/pull/70413/merge
---
2020-03-25T23:47:10.4059928Z  ---> 3fc1b512c57b
2020-03-25T23:47:10.4060260Z Step 6/7 : ENV RUN_CHECK_WITH_PARALLEL_QUERIES 1
2020-03-25T23:47:10.4062092Z  ---> Using cache
2020-03-25T23:47:10.4062514Z  ---> 5ee4295733f4
2020-03-25T23:47:10.4064168Z Step 7/7 : ENV SCRIPT python2.7 ../x.py test src/tools/expand-yaml-anchors &&            python2.7 ../x.py check --target=i686-pc-windows-gnu --host=i686-pc-windows-gnu &&            python2.7 ../x.py build --stage 0 src/tools/build-manifest &&            python2.7 ../x.py test --stage 0 src/tools/compiletest &&            python2.7 ../x.py test src/tools/tidy &&            /scripts/validate-toolstate.sh
2020-03-25T23:47:10.4069047Z  ---> 3d07a0fa42fe
2020-03-25T23:47:10.4105994Z Successfully built 3d07a0fa42fe
2020-03-25T23:47:10.4140880Z Successfully tagged rust-ci:latest
2020-03-25T23:47:10.4426942Z Built container sha256:3d07a0fa42feb5754fc13bb2f7010ebe13e4b8b8cdbebed0c75d8da320c8c8ad
---
2020-03-25T23:50:54.7570973Z     Checking rustc_attr v0.0.0 (/checkout/src/librustc_attr)
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---
2020-03-25T23:52:43.8108705Z configure: build.locked-deps    := True
2020-03-25T23:52:43.8109026Z configure: llvm.ccache          := sccache
2020-03-25T23:52:43.8109521Z configure: build.cargo-native-static := True
2020-03-25T23:52:43.8110037Z configure: dist.missing-tools   := True
2020-03-25T23:52:43.8110649Z configure: build.configure-args := ['--enable-sccache', '--disable-manage-submodu ...
2020-03-25T23:52:43.8111229Z configure: writing `config.toml` in current directory
2020-03-25T23:52:43.8111472Z configure: 
2020-03-25T23:52:43.8111905Z configure: run `python /checkout/x.py --help`
2020-03-25T23:52:43.8112137Z configure: 
---
2020-03-25T23:54:09.2252943Z Hugepagesize:       2048 kB
2020-03-25T23:54:09.2253186Z DirectMap4k:      126912 kB
2020-03-25T23:54:09.2253411Z DirectMap2M:     4067328 kB
2020-03-25T23:54:09.2253636Z DirectMap1G:     5242880 kB
2020-03-25T23:54:09.2304915Z + python2.7 ../x.py test src/tools/expand-yaml-anchors
2020-03-25T23:54:10.5535603Z Ensuring the YAML anchors in the GitHub Actions config were expanded
2020-03-25T23:54:10.5535603Z Ensuring the YAML anchors in the GitHub Actions config were expanded
2020-03-25T23:54:10.5540469Z Building stage0 tool expand-yaml-anchors (x86_64-unknown-linux-gnu)
2020-03-25T23:54:10.7896568Z    Compiling unicode-xid v0.2.0
2020-03-25T23:54:10.9315620Z    Compiling syn v1.0.11
2020-03-25T23:54:11.7521340Z    Compiling linked-hash-map v0.5.2
2020-03-25T23:54:11.7871651Z    Compiling lazy_static v1.4.0
2020-03-25T23:54:11.7871651Z    Compiling lazy_static v1.4.0
2020-03-25T23:54:11.9841109Z    Compiling yaml-rust v0.4.3
2020-03-25T23:54:16.1702869Z    Compiling quote v1.0.2
2020-03-25T23:54:30.1518837Z    Compiling thiserror-impl v1.0.5
2020-03-25T23:54:34.7677264Z    Compiling thiserror v1.0.5
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2020-03-25T23:54:35.9996734Z    Compiling expand-yaml-anchors v0.1.0 (/checkout/src/tools/expand-yaml-anchors)
2020-03-25T23:54:38.1228939Z Build completed successfully in 0:00:28
2020-03-25T23:54:38.1236609Z + python2.7 ../x.py check --target=i686-pc-windows-gnu --host=i686-pc-windows-gnu
2020-03-25T23:54:38.3657862Z     Finished dev [unoptimized] target(s) in 0.17s
2020-03-25T23:54:39.4454511Z Checking rustdoc artifacts (x86_64-unknown-linux-gnu -> i686-pc-windows-gnu)
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2020-03-25T23:56:41.2191452Z     Checking rustc_attr v0.0.0 (/checkout/src/librustc_attr)
2020-03-25T23:56:41.6919391Z     Checking rustc_parse v0.0.0 (/checkout/src/librustc_parse)
2020-03-25T23:56:43.7171106Z     Checking rustc_ast_passes v0.0.0 (/checkout/src/librustc_ast_passes)
2020-03-25T23:56:44.4153234Z     Checking rustc_expand v0.0.0 (/checkout/src/librustc_expand)
2020-03-25T23:56:44.5212481Z     Checking rustc_query_system v0.0.0 (/checkout/src/librustc_query_system)
2020-03-25T23:56:46.2333916Z     Checking rustc_builtin_macros v0.0.0 (/checkout/src/librustc_builtin_macros)
2020-03-25T23:57:06.0593987Z     Checking rustc_infer v0.0.0 (/checkout/src/librustc_infer)
2020-03-25T23:57:09.0131962Z     Checking rustc_save_analysis v0.0.0 (/checkout/src/librustc_save_analysis)
2020-03-25T23:57:09.0316439Z     Checking rustc_symbol_mangling v0.0.0 (/checkout/src/librustc_symbol_mangling)
---
2020-03-26T00:00:50.2016647Z Diff in /checkout/src/librustc_mir_build/hair/pattern/_match.rs at line 1719:
2020-03-26T00:00:50.2017494Z              Some(hir_id),
2020-03-26T00:00:50.2017908Z          )
2020-03-26T00:00:50.2018278Z          .into_iter()
2020-03-26T00:00:50.2019884Z -        .map(|c| is_useful_specialized(cx, matrix, v, c, pcx.ty, witness_preference, hir_id, is_under_guard))
2020-03-26T00:00:50.2021247Z +        .map(|c| {
2020-03-26T00:00:50.2021653Z +            is_useful_specialized(
2020-03-26T00:00:50.2022333Z +                matrix,
2020-03-26T00:00:50.2022646Z +                v,
2020-03-26T00:00:50.2022961Z +                c,
2020-03-26T00:00:50.2025991Z +                pcx.ty,
2020-03-26T00:00:50.2025991Z +                pcx.ty,
2020-03-26T00:00:50.2026417Z +                witness_preference,
2020-03-26T00:00:50.2026793Z +                hir_id,
2020-03-26T00:00:50.2027129Z +                is_under_guard,
2020-03-26T00:00:50.2027447Z +            )
2020-03-26T00:00:50.2027742Z +        })
2020-03-26T00:00:50.2028076Z          .find(|result| result.is_useful())
2020-03-26T00:00:50.2028440Z          .unwrap_or(NotUseful)
2020-03-26T00:00:50.2029167Z Diff in /checkout/src/librustc_mir_build/hair/pattern/_match.rs at line 1753:
2020-03-26T00:00:50.2029167Z Diff in /checkout/src/librustc_mir_build/hair/pattern/_match.rs at line 1753:
2020-03-26T00:00:50.2029752Z              split_grouped_constructors(cx.tcx, cx.param_env, pcx, all_ctors, matrix, DUMMY_SP, None)
2020-03-26T00:00:50.2030569Z                  .map(|c| {
2020-03-26T00:00:50.2030569Z                  .map(|c| {
2020-03-26T00:00:50.2031661Z -                    is_useful_specialized(cx, matrix, v, c, pcx.ty, witness_preference, hir_id, is_under_guard)
2020-03-26T00:00:50.2038189Z +                    is_useful_specialized(
2020-03-26T00:00:50.2038993Z +                        matrix,
2020-03-26T00:00:50.2039331Z +                        v,
2020-03-26T00:00:50.2039680Z +                        c,
2020-03-26T00:00:50.2040022Z +                        pcx.ty,
2020-03-26T00:00:50.2040022Z +                        pcx.ty,
2020-03-26T00:00:50.2040394Z +                        witness_preference,
2020-03-26T00:00:50.2093072Z +                        hir_id,
2020-03-26T00:00:50.2093864Z +                        is_under_guard,
2020-03-26T00:00:50.2094266Z +                    )
2020-03-26T00:00:50.2094608Z                  })
2020-03-26T00:00:50.2094972Z                  .find(|result| result.is_useful())
2020-03-26T00:00:50.2095367Z                  .unwrap_or(NotUseful)
2020-03-26T00:00:50.2095824Z Diff in /checkout/src/librustc_mir_build/hair/pattern/_match.rs at line 1760:
2020-03-26T00:00:50.2096228Z          } else {
2020-03-26T00:00:50.2096605Z              let matrix = matrix.specialize_wildcard();
2020-03-26T00:00:50.2096996Z              let v = v.to_tail();
2020-03-26T00:00:50.2097979Z -            let usefulness = is_useful(cx, &matrix, &v, witness_preference, hir_id, is_under_guard, false);
2020-03-26T00:00:50.2098496Z +            let usefulness =
2020-03-26T00:00:50.2098951Z +                is_useful(cx, &matrix, &v, witness_preference, hir_id, is_under_guard, false);
2020-03-26T00:00:50.2099351Z  
2020-03-26T00:00:50.2099939Z              // In this case, there's at least one "free"
2020-03-26T00:00:50.2100398Z              // constructor that is only matched against by
2020-03-26T00:00:50.2103348Z Running `"/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/rustfmt" "--config-path" "/checkout" "--edition" "2018" "--unstable-features" "--skip-children" "--check" "/checkout/src/librustc_mir_build/hair/pattern/_match.rs"` failed.
2020-03-26T00:00:50.2104635Z If you're running `tidy`, try again with `--bless` flag. Or, you just want to format code, run `./x.py fmt` instead.
2020-03-26T00:00:50.2105761Z Build completed unsuccessfully in 0:00:41
2020-03-26T00:00:50.2106134Z == clock drift check ==
2020-03-26T00:00:50.2113389Z   local time: Thu Mar 26 00:00:50 UTC 2020
2020-03-26T00:00:50.4990636Z   network time: Thu, 26 Mar 2020 00:00:50 GMT
2020-03-26T00:00:50.4990636Z   network time: Thu, 26 Mar 2020 00:00:50 GMT
2020-03-26T00:00:50.4994479Z == end clock drift check ==
2020-03-26T00:00:51.8601642Z 
2020-03-26T00:00:51.8678372Z ##[error]Bash exited with code '1'.
2020-03-26T00:00:51.8694052Z ##[section]Finishing: Run build
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2020-03-26T00:00:51.8754589Z Version      : 1.0.0
2020-03-26T00:00:51.8754822Z Author       : Microsoft
2020-03-26T00:00:51.8754822Z Author       : Microsoft
2020-03-26T00:00:51.8755205Z Help         : [More Information](https://go.microsoft.com/fwlink/?LinkId=798199)
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2020-03-26T00:00:52.2429766Z Terminate orphan process: pid (3530) (python)
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varkor · 2020-03-26T15:21:30Z

@AminArria: could you rebase the three implementation-related commits into one? It's fine to have a separate commit for the tests. This just helps to keep the git history a little cleaner. After that, this all looks good, thanks!

- Added is_under_guard parameter to _match::is_useful and only add to the matrix if false - Added comments explaining behavior

AminArria · 2020-03-26T15:42:24Z

@varkor did the rebase

varkor · 2020-03-26T17:28:23Z

Thank you!

@bors r=Centril,Nadrieril,varkor rollup

bors · 2020-03-26T17:28:24Z

📌 Commit ae7fa30 has been approved by Centril,Nadrieril,varkor

…arning, r=Centril,Nadrieril,varkor Fix incorrect pattern warning "unreachable pattern" Fixes rust-lang#70372 Added `is_under_guard` parameter to `_match::is_useful` and only add it to the matrix if `false` Tested with: ```rust #![feature(or_patterns)] fn main() { match (3,42) { (a,_) | (_,a) if a > 10 => {println!("{}", a)} _ => () } match Some((3,42)) { Some((a, _)) | Some((_, a)) if a > 10 => {println!("{}", a)} _ => () } match Some((3,42)) { Some((a, _) | (_, a)) if a > 10 => {println!("{}", a)} _ => () } } ```

@ghost

Rollup of 6 pull requests Successful merges: - rust-lang#70384 (Refactor object file handling) - rust-lang#70397 (add 'fn write_u16s' to Memory) - rust-lang#70413 (Fix incorrect pattern warning "unreachable pattern") - rust-lang#70428 (`error_bad_item_kind`: add help text) - rust-lang#70429 (Clean up E0459 explanation) - rust-lang#70437 (Miri float->int casts: be explicit that this is saturating) Failed merges: r? @ghost

rust-highfive assigned estebank Mar 25, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Mar 25, 2020

Centril reviewed Mar 25, 2020

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rust-highfive assigned varkor and unassigned estebank Mar 25, 2020

Centril added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. F-or_patterns `#![feature(or_patterns)]` and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Mar 25, 2020

Centril reviewed Mar 26, 2020

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Centril added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Mar 26, 2020

Nadrieril approved these changes Mar 26, 2020

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AminArria added 2 commits March 26, 2020 12:34

Fix incorrect pattern warning "unreachable pattern"

5796e6e

- Added is_under_guard parameter to _match::is_useful and only add to the matrix if false - Added comments explaining behavior

Add tests based on issue rust-lang#70372 comments

ae7fa30

AminArria force-pushed the match-pattern-incorrect-warning branch from e9539f0 to ae7fa30 Compare March 26, 2020 15:36

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 Mar 26, 2020

Dylan-DPC-zz mentioned this pull request Mar 26, 2020

Rollup of 6 pull requests #70438

Closed

Dylan-DPC-zz mentioned this pull request Mar 26, 2020

Rollup of 6 pull requests #70441

Merged

bors merged commit c640b95 into rust-lang:master Mar 27, 2020

AminArria deleted the match-pattern-incorrect-warning branch March 27, 2020 04:13

Centril mentioned this pull request Mar 27, 2020

Tracking issue for RFC 2535, 2530, 2175, "Or patterns, i.e Foo(Bar(x) | Baz(x))" #54883

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Fix incorrect pattern warning "unreachable pattern" #70413

Fix incorrect pattern warning "unreachable pattern" #70413

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bors commented Mar 26, 2020

Fix incorrect pattern warning "unreachable pattern" #70413

Fix incorrect pattern warning "unreachable pattern" #70413

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