Better diagnostic when pattern matching tuple structs

[MaciejWas]

Fixes #108284

When trying to pattern match a tuple struct we might get a flawed error message if there are missing fields. E.g.

let x = Foo(100, 200);
if let Foo { 0: bar } = x { ... }

Produces this error:

error[E0769]: tuple variant `Foo` written as struct variant
 --> hello.rs:5:12
  |
5 |     if let Foo { 0: foo } = x {
  |            ^^^^^^^^^^^^^^
  |
help: use the tuple variant pattern syntax instead
  |
5 |     if let Foo(_, _) = x {
  |               ~~~~~~

Which doesn't highlight that we can still use the struct syntax but we need to fill missing fields. This pr changes this error to:

error[E0027]: pattern does not mention field `1`
 --> hello.rs:5:12
  |
5 |     if let Foo { 0: foo } = x {
  |            ^^^^^^^^^^^^^^ missing field `1`
  |
help: include the missing field in the pattern
  |
5 |     if let Foo { 0: foo, 1: _ } = x {
  |                        ~~~~~~~~
help: if you don't care about this missing field, you can explicitly ignore it
  |
5 |     if let Foo { 0: foo, .. } = x {
  |                        ~~~~~~

[rustbot]

r? @jackh726

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

[MaciejWas]

@rustbot label +A-diagnostics

[jackh726]

@bors r+

[bors]

📌 Commit 3b38dd9 has been approved by jackh726

It is now in the queue for this repository.

[bors]

⌛ Testing commit 3b38dd9 with merge 696aaad...

[bors]

☀️ Test successful - checks-actions
Approved by: jackh726
Pushing 696aaad to master...

[rust-timer]

Finished benchmarking commit (696aaad): comparison URL.

Overall result: ❌ regressions - ACTION NEEDED

Next Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please open an issue or create a new PR that fixes the regressions, add a comment linking to the newly created issue or PR, and then add the perf-regression-triaged label to this PR.

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Warning ⚠: The following benchmark(s) failed to build:

• rustc
• cargo-0.60.0
• stm32f4-0.14.0

cc @rust-lang/wg-compiler-performance

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	6.4%	[3.1%, 9.1%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	6.4%	[3.1%, 9.1%]	3

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.6%	[0.6%, 0.6%]	1
Regressions ❌ (secondary)	2.3%	[2.3%, 2.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.6%	[-2.7%, -2.4%]	2
All ❌✅ (primary)	0.6%	[0.6%, 0.6%]	1

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	5.1%	[2.7%, 6.9%]	3
Regressions ❌ (secondary)	2.2%	[2.2%, 2.2%]	1
Improvements ✅ (primary)	-2.6%	[-2.6%, -2.6%]	1
Improvements ✅ (secondary)	-2.7%	[-2.7%, -2.7%]	1
All ❌✅ (primary)	3.2%	[-2.6%, 6.9%]	4

[rylev]

Looks like the regression was a blip as the next run reverses the regressions.

@rustbot label +perf-regression-triaged