[6.0] Fix request cycle in macro expansion mangling #74299
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... even in noassert builds. This is always a miscompile and should be prevented.
Fixes rdar://127078338.
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@swift-ci Please test |
hborla
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Jun 11, 2024
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swiftlang/llvm-project#8894 |
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6.0 cherry-pick of #74201
Description: Expanding a macro inside a local function with autoclosures would attempt to assign discriminators before the autoclosures had been formed. As a result, SILGen would emit autoclosures with duplicate symbol names. This would either cause a silent miscompile or diagnose an error about mismatched SIL function types. This PR changes the macro expansion buffer mangling to use the source location of the expansion instead. This avoids evaluating requests before everything has been type checked.
Origination: This never worked, but it's become more common now that the
with.*Continuationfunctions have a default argument that expands the#isolationmacro. These APIs are often used with local functions.Radar: Fixes rdar://127078338.
Risk: Low. However, to avoid silent miscompiles in the future, this converts the absence of a discriminator into a fatal error. This is a major invariant violation which should always be flagged, even in noassert builds.
Reviewed by: @DougGregor