Implement lldb formatter for "clang encoded" enums (LLDB 18.1+) (V3)

[VladimirMakaev]

This is a redo of PR (#124458) which was approved previously but force-pushed out. Then a V2 (#124745) failed debuginfo\msvc-pretty-enums.rs test during merge.

I've fixed the test and checked it to pass on Windows with .\x.ps1 test .\tests\debuginfo\msvc-pretty-enums.rs

Below is the original summary:

Summary:

fixes #79530

I landed a fix last year to enable DW_TAG_variant_part encoding in LLDBs (https://reviews.llvm.org/D149213). This PR is a corresponding fix in synthetic formatters to decode that information.

This is in no way perfect implementation but at least it improves the status quo. But most types of enums will be visible and debuggable in some way.

I've also updated most of the existing tests that touch enums and re-enabled test cases based on LLDB for enums.

Test Plan:

ran tests ./x test tests/debuginfo/. Also tested manually in LLDB CLI and LLDB VSCode

Other Thoughs:

A better approach would probably be adopting formatters from codelldb. There is some neat hack that hooks up summary provider via synthetic provider which can ultimately fix more display issues for Rust types and enums too. But getting it to work well might take more time that I have right now.

[rustbot]

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[dtolnay]

This is the diff from v1:

diff --git a/tests/debuginfo/coroutine-objects.rs b/tests/debuginfo/coroutine-objects.rs
@@ -27,7 +27,7 @@

 // lldb-command:run
 // lldb-command:v b
-// lldb-check:(coroutine_objects::main::{coroutine_env#0}) b = { value = { _ref__a = 0x[...] } $discr$ = ',' }
+// lldb-check:(coroutine_objects::main::{coroutine_env#0}) b = { value = { _ref__a = 0x[...] } $discr$ = [...] }

 // === CDB TESTS ===================================================================================

diff --git a/tests/debuginfo/msvc-pretty-enums.rs b/tests/debuginfo/msvc-pretty-enums.rs
@@ -3,8 +3,8 @@
 //@ compile-flags:-g

 // === LLDB TESTS ==================================================================================
-
 // lldb-command:run
+
 // lldb-command:v a
 // lldbg-check:(core::option::Option<msvc_pretty_enums::CStyleEnum>) a = { value = { 0 = Low } }

@@ -74,12 +74,7 @@
 // lldbg-check:(msvc_pretty_enums::ArbitraryDiscr) arbitrary_discr2 = { value = { 0 = 5678 } $discr$ = 5000000 }

 // === CDB TESTS ==================================================================================
-// cdb-command: g
-//
-// cdb-command: dx a
-// cdb-check:a                : Some [Type: enum2$<core::option::Option<msvc_pretty_enums::CStyleEnum> >]
-// cdb-check:    [+0x000] __0              : Low (0x2) [Type: msvc_pretty_enums::CStyleEnum]
-//
+
 // cdb-command: g
 //
 // cdb-command: dx a

[dtolnay]

Thank you!

[dtolnay]

@bors r+

[bors]

📌 Commit fb2d9cd has been approved by dtolnay

It is now in the queue for this repository.

[bors]

⌛ Testing commit fb2d9cd with merge 60a7c19...

[bors]

☀️ Test successful - checks-actions
Approved by: dtolnay
Pushing 60a7c19 to master...

[rust-timer]

Finished benchmarking commit (60a7c19): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.8%	[-2.2%, -1.5%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-1.8%	[-2.2%, -1.5%]	3

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)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.9%	[-3.5%, -2.2%]	2
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 675.387s -> 676.069s (0.10%)
Artifact size: 315.97 MiB -> 315.95 MiB (-0.01%)