Restore legacy cross-assembly inline metadata by T-Gro · Pull Request #20260 · dotnet/fsharp

T-Gro · 2026-08-13T20:14:13Z

Fixes#20253

F# 4.7 and earlier encoded required inline values with flag bits now used by InlinedDefinition, causing newer compilers to emit calls to dynamic-invocation stubs. Normalize legacy flags while importing metadata.

Regression fixture: LegacyInline.dll built with .NET SDK 10.0.105 (F# compiler without ValInline.InlinedDefinition). That compiler used the pre-InlinedDefinition encoding where ValInline.Always = 0x00 bits. The current compiler reads 0x00 as InlinedDefinition (ShouldInline=false). With --optimize-, crossAssemblyOpt() returns false and ShouldInline=false, so the body is never fetched; the optimizer emits a direct IL call instead of the inlined form expected for an `inline` function. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Replace the arithmetic-only `increment` fixture with a cross-assembly inline SRTP function whose compiled (non-inlined) fallback body is the compiler-generated "Dynamic invocation of Invoke is not supported" placeholder, matching the shape of the real-world regression (issue 20253, Aether's op_HatEquals). LegacyInline.dll is regenerated from the updated LegacyInline.fs with the official .NET SDK 10.0.105 F# compiler. The test now exercises Release/optimized codegen (withOptimize) and compiles+runs the consumer, asserting no direct call to the placeholder remains in the imported IL. Note: exhaustive testing against SDK 10.0.100/10.0.105/10.0.203/10.0.301 shows none of these official compilers actually emit the ambiguous zero-bit ValInline encoding for this shape (SRTP trait resolution and witness-passing both resolve the call at the consumer's type-check time, independent of the ShouldInline metadata bit), so this fixture does not currently reproduce a failing run against HEAD. It does correctly validate the cross-assembly SRTP import path and regresses if a future change reintroduces a direct call to the placeholder body. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Build LegacyInline.dll with the official .NET SDK 3.1.100 F# compiler (10.7.0.0 for F# 4.7), which predates witness metadata and preserves the legacy inline encoding. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Refactor Issue 20253 test to focus on IL verification, removing runtime execution that doesn't contribute to the regression contract. The test now compiles as a library and verifies that the legacy inline metadata from LegacyInline.dll is properly inlined, preventing the direct call to LegacyInline.Library::invoke from appearing in the emitted IL. This change: - Simplifies Consumer module from EntryPoint program to library function - Removes runtime execution verification (run | shouldSucceed | verifyOutputContains) - Retains compile success verification (shouldSucceed) - Maintains IL regression assertion (verifyILNotPresent [ "LegacyInline.Library::invoke" ]) The IL assertion is the actual regression contract for this issue. Co-authored-by: Copilot <copilot@example.com>

u_ValData deserialized ValFlags directly from the pickled int64, so DLLs written by compilers <= 4.7 (pre-witness), which encoded PseudoVal/Always inline info as all-zero inline bits, were imported as ValInline.InlinedDefinition after PR dotnet#19548 repurposed the same 0x00 bits for that case. Add ValFlags.OfPickledBits, mirroring the InlinedDefinition -> Always normalization PickledBits already applies on write, and use it in u_ValData so legacy zero-bit values import as Always (ShouldInline=true) regardless of which compiler wrote them. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Compile the Issue 20253 consumer out-of-process via runFscProcess instead of CompilerAssert.CompileRaw in-process. The in-process path can mutate shared compiler/import state across tests sharing the same process, so keep this legacy pre-witness FSharp.Core regression check at the IL boundary without touching the test host's own state. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Tomas Grosup <Tomas.Grosup@gmail.com>

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

github-actions · 2026-08-13T20:14:27Z

❗ Release notes required

You can open this PR in browser to add release notes: open in github.dev

✅ Found changes and release notes in following paths:

Change path Release notes path Description
`src/Compiler` docs/release-notes/.FSharp.Compiler.Service/11.0.100.md

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: d9bb5fd2-ae26-4369-934d-1bae177a1266

T-Gro · 2026-08-14T10:52:49Z

cc @auduchinok

auduchinok · 2026-08-14T13:07:51Z

@T-Gro Thanks for fixing it!

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: d9bb5fd2-ae26-4369-934d-1bae177a1266

github-actions · 2026-08-14T13:54:28Z

🔍 Tooling Safety Check — Affects-Agent-Config, Affects-Compiler-Output
Affects-Agent-Config: modifies .github/instructions/TypedTreePickle.instructions.md
Affects-Compiler-Output: changes metadata import flag normalization in TypedTree/TypedTreePickle

Generated by PR Tooling Safety Check · opus46 3.1M · ◷

T-Gro · 2026-08-16T14:08:17Z

/backport to release/10.0.4xx

github-actions · 2026-08-16T14:08:26Z

Started backporting to release/10.0.4xx (link to workflow run)

Chiron's chiron-6 branch serializes through Aether 8.2.0's `inline` SRTP optics, which reproduces the SDK 10.0.400 legacy cross-assembly inline-metadata regression (#20253, fixed by #20260). The bug is runtime-only: a compiler that misreads Aether's legacy pickled inline flag drops the inline body and emits a call to the dynamic-invocation stub, so the build stays clean but System.NotSupportedException is thrown at run time. The matrix entry therefore runs Chiron's own xunit suite; a build-only check would pass despite the bug. Two sed edits only retarget dead frameworks (the library's net452 leg cannot restore on a current SDK; the test project targets the removed netcoreapp2.0) and change no test logic. Verified: 11 tests fail with NotSupportedException on SDK 10.0.400, and all pass with the compiler built from main. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Chiron's chiron-6 branch serializes through Aether 8.2.0's `inline` SRTP optics, which reproduces the SDK 10.0.400 legacy cross-assembly inline-metadata regression (#20253, fixed by #20260). The bug is runtime-only: a compiler that misreads Aether's legacy pickled inline flag drops the inline body and emits a call to the dynamic-invocation stub, so the build stays clean but System.NotSupportedException is thrown at run time. The matrix entry therefore runs Chiron's own xunit suite, filtered to the Aether Optic get/set/map tests that exercise the miscompiled path; a build-only check would pass despite the bug. Two sed edits only retarget dead frameworks (the library's net452 leg cannot restore on a current SDK; the test project targets the removed netcoreapp2.0) and change no test logic. Verified: the Optic tests fail with NotSupportedException on SDK 10.0.400, and all pass with the compiler built from main. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

T-Gro · 2026-08-21T19:44:57Z

/backport to release/dev18.9

github-actions · 2026-08-21T19:45:07Z

Started backporting to release/dev18.9 (link to workflow run)

T-Gro · 2026-08-21T19:45:12Z

/backport to release/dev18.10

github-actions · 2026-08-21T19:45:20Z

Started backporting to release/dev18.10 (link to workflow run)

github-actions · 2026-08-21T19:45:51Z

@T-Gro an error occurred while backporting to release/dev18.10. See the workflow output for details.

github-actions · 2026-08-21T19:46:00Z

@T-Gro an error occurred while backporting to release/dev18.9. See the workflow output for details.

T-Groand others added 10 commits August 13, 2026 20:25

test: align legacy inline regression name
754a7d4
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

test: quote legacy compiler paths
e39f6d8
Co-authored-by: Tomas Grosup <Tomas.Grosup@gmail.com>

test: pin legacy inline fixture semantics
3a7c86c
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

test: make legacy inline fixture reproducible
2e4f14b
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

github-project-automationBot added this to F# Compiler and Tooling Aug 13, 2026

github-project-automationBot moved this to New in F# Compiler and Tooling Aug 13, 2026

T-Groand others added 3 commits August 13, 2026 22:14

docs: note legacy inline metadata fix
28ba693
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

test: drop legacy binary fixture
bb6ead4
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: d9bb5fd2-ae26-4369-934d-1bae177a1266

test: restore untouched assembly boundary file
6ad68f1
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: d9bb5fd2-ae26-4369-934d-1bae177a1266

T-Gro requested review from abonie and auduchinok August 14, 2026 10:52

T-Gro marked this pull request as ready for review August 14, 2026 10:53

T-Gro requested a review from a team as a code owner August 14, 2026 10:53

github-actionsBot added the ⚠️ Affects-Compiler-Output Tooling check: PR touches IL emission or codegen label Aug 14, 2026

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SDK 10.0.400 regression: cross-assembly inline SRTP call throws in Release #20253
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docs: postmortem for legacy inline metadata regression
df55ec3
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: d9bb5fd2-ae26-4369-934d-1bae177a1266

github-actionsBot added the ⚠️ Affects-Agent-Config Tooling check: PR modifies AI agent instructions or workflows label Aug 14, 2026

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T-Gro merged commit 7efd608 into dotnet:mainAug 16, 2026
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[release/10.0.4xx] Restore legacy cross-assembly inline metadata #20267
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[release/11.0.1xx-rc1] Source code updates from dotnet/fsharp dotnet/dotnet#8335
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[release/11.0.1xx] Source code updates from dotnet/fsharp dotnet/dotnet#8351
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[Automated] PRs inserted in VS build main-12117.157 #20279
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[main] Source code updates from dotnet/fsharp dotnet/dotnet#8299
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Add Chiron to the compiler regression-test matrix #20281
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Restore legacy cross-assembly inline metadata - #20260

Restore legacy cross-assembly inline metadata#20260
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