Remove noisy suggestion of hash_map

[ayushmishra2005]

Removed import suggestion of std::collections::hash_map::HashMap
#72642

[rust-highfive]

r? @nikomatsakis

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

[tesuji]

The stderr files are auto-generated. You might want to change Rust file instead.

[ayushmishra2005]

The stderr files are auto-generated. You might want to change Rust file instead.

I am looking into it.

[davidtwco]

Unfortunately, this isn't enough to solve #72642. You've changed a stderr file, which is the output from the compiler for a test, which we use to make sure the compiler's output hasn't changed - changing it only makes the test fail, it doesn't change the output of the compiler.

You can grep to find that the "consider importing one of these items" help is constructed here in show_candidates:

rust/src/librustc_resolve/diagnostics.rs

Line 1498 in 0aa6751

let msg = format!("consider importing {} {}{}", determiner, kind, instead);

show_candidates takes a &[ImportSuggestion], which we can trace back to these lines:

rust/src/librustc_resolve/late/diagnostics.rs

Lines 213 to 223 in f93bb2a

	let candidates = self
	.r
	.lookup_import_candidates(ident, ns, is_expected)
	.drain(..)
	.filter(|ImportSuggestion { did, .. }| {
	match (did, res.and_then(|res| res.opt_def_id())) {
	(Some(suggestion_did), Some(actual_did)) => *suggestion_did != actual_did,
	_ => true,
	}
	})
	.collect::<Vec<_>>();

Going slightly deeper, lookup_import_candidates_from_module constructs the list of import suggestions:

rust/src/librustc_resolve/diagnostics.rs

Lines 628 to 635 in 0aa6751

	fn lookup_import_candidates_from_module<FilterFn>(
	&mut self,
	lookup_ident: Ident,
	namespace: Namespace,
	start_module: Module<'a>,
	crate_name: Ident,
	filter_fn: FilterFn,
	) -> Vec<ImportSuggestion>

You might consider experimenting with this function to de-duplicate the suggestions in some way if you're interested in addressing this issue.

[rust-highfive]

The job x86_64-gnu-llvm-8 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.

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Downloading task: Bash (3.163.2)
Checking job knob settings.
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========================== Starting Command Output ===========================
[command]/bin/bash --noprofile --norc /home/vsts/work/_temp/3e6531e3-faa6-45bb-8ab8-d0a4ee66b1dc.sh

##[section]Finishing: Disable git automatic line ending conversion
##[section]Starting: Checkout rust-lang/rust@refs/pull/72656/merge to s
Task         : Get sources
Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
Version      : 1.0.0
Author       : Microsoft
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##[command]git config gc.auto 0
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---
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Step 5/8 : ENV RUST_CONFIGURE_ARGS       --build=x86_64-unknown-linux-gnu       --llvm-root=/usr/lib/llvm-8       --enable-llvm-link-shared       --set rust.thin-lto-import-instr-limit=10
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Step 6/8 : ENV SCRIPT python2.7 ../x.py test --exclude src/tools/tidy &&            python2.7 ../x.py test src/test/mir-opt --pass=build                                   --target=armv5te-unknown-linux-gnueabi &&            python2.7 ../x.py test src/tools/tidy
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Step 7/8 : ENV NO_DEBUG_ASSERTIONS=1
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---
   Compiling fmt_macros v0.0.0 (/checkout/src/libfmt_macros)
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   Compiling rustc_ast_pretty v0.0.0 (/checkout/src/librustc_ast_pretty)
   Compiling rustc_hir v0.0.0 (/checkout/src/librustc_hir)
   Compiling rustc_query_system v0.0.0 (/checkout/src/librustc_query_system)
   Compiling chalk-solve v0.10.0
   Compiling rustc_hir_pretty v0.0.0 (/checkout/src/librustc_hir_pretty)
   Compiling rustc_parse v0.0.0 (/checkout/src/librustc_parse)
   Compiling rustc_ast_lowering v0.0.0 (/checkout/src/librustc_ast_lowering)
---
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   Compiling rustc_hir_pretty v0.0.0 (/checkout/src/librustc_hir_pretty)
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35 


The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/resolve/use_suggestion_placement/use_suggestion_placement.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args resolve/use_suggestion_placement.rs`
error: 1 errors occurred comparing output.
status: exit code: 1
status: exit code: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/resolve/use_suggestion_placement.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/resolve/use_suggestion_placement" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/resolve/use_suggestion_placement/auxiliary"
------------------------------------------

------------------------------------------
stderr:
---

error[E0412]: cannot find type `HashMap` in this scope
  --> /checkout/src/test/ui/resolve/use_suggestion_placement.rs:27:23
   |
LL |     type Dict<K, V> = HashMap<K, V>; //~ ERROR cannot find
   |
help: consider importing one of these items
   |
LL | use std::collections::HashMap;
---
thread 'main' panicked at 'Some tests failed', src/tools/compiletest/src/main.rs:348:22
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


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-8/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" "8.0.0" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"


failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test --exclude src/tools/tidy
Build completed unsuccessfully in 1:08:08
Build completed unsuccessfully in 1:08:08
== clock drift check ==
  local time: Wed May 27 15:57:49 UTC 2020
  network time: Wed, 27 May 2020 15:57:49 GMT
== end clock drift check ==

##[error]Bash exited with code '1'.
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[nikomatsakis]

Since this PR is presently empty, I'm going to close it for now -- @ayushmishra2005 feel free to re-open when it's ready for review :)

[ayushmishra2005]

Unfortunately, this isn't enough to solve #72642. You've changed a stderr file, which is the output from the compiler for a test, which we use to make sure the compiler's output hasn't changed - changing it only makes the test fail, it doesn't change the output of the compiler.

You can grep to find that the "consider importing one of these items" help is constructed here in show_candidates:

rust/src/librustc_resolve/diagnostics.rs

Line 1498 in 0aa6751

let msg = format!("consider importing {} {}{}", determiner, kind, instead);

show_candidates takes a &[ImportSuggestion], which we can trace back to these lines:

rust/src/librustc_resolve/late/diagnostics.rs

Lines 213 to 223 in f93bb2a

	let candidates = self
	.r
	.lookup_import_candidates(ident, ns, is_expected)
	.drain(..)
	.filter(|ImportSuggestion { did, .. }| {
	match (did, res.and_then(|res| res.opt_def_id())) {
	(Some(suggestion_did), Some(actual_did)) => *suggestion_did != actual_did,
	_ => true,
	}
	})
	.collect::<Vec<_>>();

Going slightly deeper, lookup_import_candidates_from_module constructs the list of import suggestions:

rust/src/librustc_resolve/diagnostics.rs

Lines 628 to 635 in 0aa6751

	fn lookup_import_candidates_from_module<FilterFn>(
	&mut self,
	lookup_ident: Ident,
	namespace: Namespace,
	start_module: Module<'a>,
	crate_name: Ident,
	filter_fn: FilterFn,
	) -> Vec<ImportSuggestion>

You might consider experimenting with this function to de-duplicate the suggestions in some way if you're interested in addressing this issue.

@davidtwco Thanks for your comment. Since I am new to Rust, so I would need more mentorship. I am still not able to figure out what is causing this issue and where hash_map is being inserted.

I also tried to check this function lookup_import_candidates.

[davidtwco]

@ayushmishra2005 I've responded in this comment - feel free to follow-up questions, good luck!