suggest `into_iter()` when `Iterator` method called on `impl IntoIterator`

[d-sonuga]

Fix for issue #117711.

[rustbot]

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[compiler-errors]

r? compiler

[bors]

:umbrella: The latest upstream changes (presumably #120722) made this pull request unmergeable. Please resolve the merge conflicts.

[rust-log-analyzer]

The job x86_64-gnu-llvm-16 failed! Check out the build log: (web) (plain)

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---
#12 writing image sha256:f9fe0979ac768bb263744510eed48c1d0386436631cc2ca95679fce9c649519b done
#12 naming to docker.io/library/rust-ci done
#12 DONE 10.0s
##[endgroup]
Setting extra environment values for docker:  --env ENABLE_GCC_CODEGEN=1 --env GCC_EXEC_PREFIX=/usr/lib/gcc/
[CI_JOB_NAME=x86_64-gnu-llvm-16]
##[group]Clock drift check
  local time: Mon Feb 12 08:50:08 UTC 2024
  network time: Mon, 12 Feb 2024 08:50:08 GMT
  network time: Mon, 12 Feb 2024 08:50:08 GMT
##[endgroup]
sccache: Starting the server...
##[group]Configure the build
configure: processing command line
configure: 
configure: build.configure-args := ['--build=x86_64-unknown-linux-gnu', '--llvm-root=/usr/lib/llvm-16', '--enable-llvm-link-shared', '--set', 'rust.thin-lto-import-instr-limit=10', '--set', 'change-id=99999999', '--enable-verbose-configure', '--enable-sccache', '--disable-manage-submodules', '--enable-locked-deps', '--enable-cargo-native-static', '--set', 'rust.codegen-units-std=1', '--set', 'dist.compression-profile=balanced', '--dist-compression-formats=xz', '--set', 'build.optimized-compiler-builtins', '--disable-dist-src', '--release-channel=nightly', '--enable-debug-assertions', '--enable-overflow-checks', '--enable-llvm-assertions', '--set', 'rust.verify-llvm-ir', '--set', 'rust.codegen-backends=llvm,cranelift,gcc', '--set', 'llvm.static-libstdcpp', '--enable-new-symbol-mangling']
configure: target.x86_64-unknown-linux-gnu.llvm-config := /usr/lib/llvm-16/bin/llvm-config
configure: llvm.link-shared     := True
configure: rust.thin-lto-import-instr-limit := 10
configure: change-id            := 99999999
---

---- [ui] tests/ui/did_you_mean/collect-without-into-iter-call.rs stdout ----
diff of stderr:

26 LL | fn process(items: impl IntoIterator<Item = String>) -> Vec<String> {
27    |                   -------------------------------- method `collect` not found for this type parameter
28 LL |     items.collect()
-    |           ^^^^^^^ `impl IntoIterator<Item = String>` is not an iterator
+    |           ^^^^^^^ method cannot be called on `impl IntoIterator<Item = String>` due to unsatisfied trait bounds
30    |
- help: call `.into_iter()` first
+    = help: items from traits can only be used if the type parameter is bounded by the trait
+ help: the following trait defines an item `collect`, perhaps you need to restrict type parameter `impl IntoIterator<Item = String>` with it:
- LL |     items.into_iter().collect()
-    |           ++++++++++++
-    |           ++++++++++++
+ LL | fn process(items: impl IntoIterator<Item = String> + Iterator) -> Vec<String> {
35 
36 error: aborting due to 3 previous errors
37 

---
--- stderr -------------------------------
error[E0599]: no method named `map` found for opaque type `impl IntoIterator<Item = i32>` in the current scope
##[error]  --> /checkout/tests/ui/did_you_mean/collect-without-into-iter-call.rs:6:29
   |
LL |     let other_items = items.map(|i| i + 1);
   |                             ^^^ `impl IntoIterator<Item = i32>` is not an iterator
   |
help: call `.into_iter()` first
Build completed unsuccessfully in 0:14:17
Build completed unsuccessfully in 0:14:17
LL |     let other_items = items.into_iter().map(|i| i + 1);

error[E0599]: no method named `collect` found for opaque type `impl IntoIterator<Item = i32>` in the current scope
##[error]  --> /checkout/tests/ui/did_you_mean/collect-without-into-iter-call.rs:8:31
   |
   |
LL |     let vec: Vec<i32> = items.collect();
   |                               ^^^^^^^ `impl IntoIterator<Item = i32>` is not an iterator
   |
help: call `.into_iter()` first
   |
LL |     let vec: Vec<i32> = items.into_iter().collect();

error[E0599]: no method named `collect` found for type parameter `impl IntoIterator<Item = String>` in the current scope
##[error]  --> /checkout/tests/ui/did_you_mean/collect-without-into-iter-call.rs:17:11
   |
   |
LL | fn process(items: impl IntoIterator<Item = String>) -> Vec<String> {
   |                   -------------------------------- method `collect` not found for this type parameter
LL |     items.collect()
   |           ^^^^^^^ method cannot be called on `impl IntoIterator<Item = String>` due to unsatisfied trait bounds
   = help: items from traits can only be used if the type parameter is bounded by the trait
   = help: items from traits can only be used if the type parameter is bounded by the trait
help: the following trait defines an item `collect`, perhaps you need to restrict type parameter `impl IntoIterator<Item = String>` with it:
   |
LL | fn process(items: impl IntoIterator<Item = String> + Iterator) -> Vec<String> {

error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0599`.

[rust-log-analyzer]

A job failed! Check out the build log: (web) (plain)

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---
#4 [auth] library/ubuntu:pull token for registry-1.docker.io
#4 DONE 0.0s

#3 [internal] load metadata for docker.io/library/ubuntu:22.04
#3 ERROR: failed to authorize: failed to fetch oauth token: unexpected status from POST request to https://auth.docker.io/token: 500 Internal Server Error
 > [internal] load metadata for docker.io/library/ubuntu:22.04:
------
Dockerfile:1
--------------------
--------------------
   1 | >>> FROM ubuntu:22.04
   2 |     
   3 |     ARG DEBIAN_FRONTEND=noninteractive
--------------------
ERROR: failed to solve: ubuntu:22.04: failed to authorize: failed to fetch oauth token: unexpected status from POST request to https://auth.docker.io/token: 500 Internal Server Error
#0 building with "default" instance using docker driver

#1 [internal] load .dockerignore
#1 transferring context: 2B done
---
#3 [auth] library/ubuntu:pull token for registry-1.docker.io
#3 DONE 0.0s

#4 [internal] load metadata for docker.io/library/ubuntu:22.04
#4 ERROR: failed to authorize: failed to fetch oauth token: unexpected status from POST request to https://auth.docker.io/token: 500 Internal Server Error
 > [internal] load metadata for docker.io/library/ubuntu:22.04:
------
Dockerfile:1
--------------------
--------------------
   1 | >>> FROM ubuntu:22.04
   2 |     
   3 |     ARG DEBIAN_FRONTEND=noninteractive
--------------------
ERROR: failed to solve: ubuntu:22.04: failed to authorize: failed to fetch oauth token: unexpected status from POST request to https://auth.docker.io/token: 500 Internal Server Error
#0 building with "default" instance using docker driver

#1 [internal] load .dockerignore
#1 transferring context: 2B done
---
#3 [auth] library/ubuntu:pull token for registry-1.docker.io
#3 DONE 0.0s

#4 [internal] load metadata for docker.io/library/ubuntu:22.04
#4 ERROR: failed to authorize: failed to fetch oauth token: unexpected status from POST request to https://auth.docker.io/token: 500 Internal Server Error
 > [internal] load metadata for docker.io/library/ubuntu:22.04:
------
Dockerfile:1
--------------------
--------------------
   1 | >>> FROM ubuntu:22.04
   2 |     
   3 |     ARG DEBIAN_FRONTEND=noninteractive
--------------------
ERROR: failed to solve: ubuntu:22.04: failed to authorize: failed to fetch oauth token: unexpected status from POST request to https://auth.docker.io/token: 500 Internal Server Error
#0 building with "default" instance using docker driver

#1 [internal] load .dockerignore
#1 transferring context: 2B done
---
#3 [auth] library/ubuntu:pull token for registry-1.docker.io
#3 DONE 0.0s

#4 [internal] load metadata for docker.io/library/ubuntu:22.04
#4 ERROR: failed to authorize: failed to fetch oauth token: unexpected status from POST request to https://auth.docker.io/token: 500 Internal Server Error
 > [internal] load metadata for docker.io/library/ubuntu:22.04:
------
Dockerfile:1
--------------------
--------------------
   1 | >>> FROM ubuntu:22.04
   2 |     
   3 |     ARG DEBIAN_FRONTEND=noninteractive
--------------------
ERROR: failed to solve: ubuntu:22.04: failed to authorize: failed to fetch oauth token: unexpected status from POST request to https://auth.docker.io/token: 500 Internal Server Error
#0 building with "default" instance using docker driver

#1 [internal] load .dockerignore
#1 transferring context: 2B done
---
#3 [auth] library/ubuntu:pull token for registry-1.docker.io
#3 DONE 0.0s

#4 [internal] load metadata for docker.io/library/ubuntu:22.04
#4 ERROR: failed to authorize: failed to fetch oauth token: unexpected status from POST request to https://auth.docker.io/token: 500 Internal Server Error
 > [internal] load metadata for docker.io/library/ubuntu:22.04:
------
Dockerfile:1
--------------------
--------------------
   1 | >>> FROM ubuntu:22.04
   2 |     
   3 |     ARG DEBIAN_FRONTEND=noninteractive
--------------------
ERROR: failed to solve: ubuntu:22.04: failed to authorize: failed to fetch oauth token: unexpected status from POST request to https://auth.docker.io/token: 500 Internal Server Error
##[error]Process completed with exit code 1.
Post job cleanup.

[compiler-errors]

@bors r+ rollup

[bors]

:pushpin: Commit e99766d885a9a2c714aa58e06712d30a96b24514 has been approved by compiler-errors

It is now in the queue for this repository.