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LifetimeDependence: Support function types#86842

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swiftlang:mainfrom
aidan-hall:just-func-type-lifetimes-try-print
Feb 6, 2026
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LifetimeDependence: Support function types#86842
aidan-hall merged 8 commits into
swiftlang:mainfrom
aidan-hall:just-func-type-lifetimes-try-print

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@aidan-hall aidan-hall commented Jan 28, 2026 •
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First part of work originally from #85414.
Supersedes #86795.

The approach taken in this PR is as follows:

  1. Enable lifetime attribute parsing and lifetime inference for function types.
  2. When printing a Swift type, print a @_lifetime annotation using parameter labels when possible.
  3. If a target or source parameter does not have a label, fall back to printing indices. In swiftinterface files, do not print that lifetime, under the assumption that it was inferred.

@aidan-hall aidan-hall self-assigned this Jan 28, 2026
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slavapestov commented Jan 28, 2026

Yeah, one of the fundamental invariants in the AST is that Types are supposed to be immutable, and uniqued. Let's not violate that for any reason.

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Comment thread include/swift/AST/LifetimeDependence.h Outdated
@aidan-hall aidan-hall changed the title LifetimeDependence: Support function types without modifying LifetimeDependenceInfo LifetimeDependence: Support function types Jan 28, 2026
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@aidan-hall aidan-hall force-pushed the just-func-type-lifetimes-try-print branch 2 times, most recently from 23f51f0 to 2275893 Compare January 29, 2026 16:22
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meg-gupta commented Jan 29, 2026 •
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Can you add some tests to cover SIL lifetime diagnostics and function types? test/SILOptimizer/lifetime_dependence/lifetime_dependence_borrow_fail.swift and test/SILOptimizer/lifetime_dependence/lifetime_dependence_copy_fail.swift have some examples with function declarations.

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aidan-hall commented Feb 5, 2026

@swift-ci test macos

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aidan-hall commented Feb 5, 2026

@swift-ci test linux

@aidan-hall aidan-hall force-pushed the just-func-type-lifetimes-try-print branch from 33121ed to 482c695 Compare February 5, 2026 12:46
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aidan-hall commented Feb 5, 2026

@swift-ci test

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aidan-hall commented Feb 5, 2026

@swift-ci smoke test

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aidan-hall commented Feb 5, 2026

@swift-ci please test source compatibility

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LifetimeDependence: Fix issues from earlier refactor
f39359e 
This addresses feedback from swiftlang#86560:
- Remove redundant collectParameterInfo call
- Consistent naming of ParamInfo variables
- Explicit type name instead of decltype

Also add nullptr checks on afd, as appropriate.
@aidan-hall aidan-hall force-pushed the just-func-type-lifetimes-try-print branch 2 times, most recently from 142e117 to 7e903f8 Compare February 5, 2026 12:58
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@swift-ci test

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@swift-ci smoke test

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@swift-ci test source compatibility

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Serialization: Add LifetimeDependenceInfo.isFromAnnotation to module …
fbb2da1 
…format

The isFromAnnotation flag is set if and only if the lifetime originates from a
@Lifetime or @_lifetime annotation in the source program.

isFromAnnotation==false means that the lifetime dependence checker would infer
the same lifetime if the Swift type or decl was printed without an annotation
for that dependency. More specifically, it means that the depenence was inferred
by the lifetime dependence checker.

Some dependencies on imported C/C++ decls are "inferred", but they either
correspond to explicit lifetime information in the source (smart pointers,
lifetimebound attribute) or are likely to differ from what the dependence
checker would infer. As such, we set the flag to true for all of them.
@aidan-hall
Types: + AnyFunctionType::hasExplicitLifetimeDependencies
b2c7921
@aidan-hall
Add language feature ClosureLifetimes
805d8e9
@aidan-hall
[AST] Support multiple of the same attribute per type
e401b1a
@aidan-hall
LifetimeDependence: Support function types
7b9db38 
To a function type's lifetimes, a base version of the type is first created with
no lifetime dependence info. This is then passed to the dependence checker, and
the resulting dependencies are added to it.

It would be possible to do this analysis by passing just the parameter list and
result type (which are available before the type is created), but this approach
lets us avoid dealing with a header inclusion cycle between Types.h, ExtInfo.h,
and LifetimeDependence.h, since it does not require AnyFunctionType::Param to be
defined in LifetimeDependence.h.
@aidan-hall
[AST] Print function type LifetimeDependenceInfo using parameter labels
a366c47 
We fall back to indices when labels are not available, but labels are
preferable, because they readable, stable, and preferred by the lifetime
dependencies proposal.
@aidan-hall
LifetimeDependence: Tests for function type attribute
6aa5578 
Includes:
- rdar://166912068 test case
- Nested type SIL tests
- rdar://160894371 test
- Many more
@aidan-hall aidan-hall force-pushed the just-func-type-lifetimes-try-print branch from 7e903f8 to 6aa5578 Compare February 5, 2026 14:50
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@swift-ci smoke test

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aidan-hall commented Feb 5, 2026

@swift-ci test

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aidan-hall commented Feb 5, 2026

@swift-ci test source compatibility

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LGTM!

@aidan-hall aidan-hall merged commit e98a7a6 into swiftlang:main Feb 6, 2026
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atrick added a commit to atrick/swift that referenced this pull request Feb 24, 2026
@atrick
Fix lifetime type checking for nonescaping closures
b0c5e34 
A nonescaping closure that returns a ~Escapable result and has no @_lifetime
annotation is assumed to depend on its closure context.

This fixes overly strict type checking introduced by:

    commit e98a7a6
    Date:   Fri Feb 6 02:09:25 2026
    Merge pull request swiftlang#86842
    LifetimeDependence: Support function types

Fix:

1. Disable missing dependency diagnostics for ~Escapable results

Continue allow the most basic nonescaping closure types without annotation:

    func f(body: () -> NE) -> NE

2. Disable single-parameter inference for function types

Do *not* infer a default parameter dependency here:

    func f(body: (AnyObject) -> NE) -> NE

The single-parameter rule should only apply to unambiguous function
declarations. It never applies to function types. Function types should instead
infer a dependency on the closure context.

Fixes rdar://171031632 ([nonescapable] allow nonescaping closures to return
non-Escapable types)
atrick added a commit to atrick/swift that referenced this pull request Feb 24, 2026
@atrick
Fix lifetime type checking for nonescaping closures
3ff7782 
A nonescaping closure that returns a ~Escapable result and has no @_lifetime
annotation is assumed to depend on its closure context.

This fixes overly strict type checking introduced by:

    commit e98a7a6
    Date:   Fri Feb 6 02:09:25 2026
    Merge pull request swiftlang#86842
    LifetimeDependence: Support function types

Fix:

1. Disable missing dependency diagnostics for ~Escapable results

Continue allow the most basic nonescaping closure types without annotation:

    func f(body: () -> NE) -> NE

2. Disable single-parameter inference for function types

Do *not* infer a default parameter dependency here:

    func f(body: (AnyObject) -> NE) -> NE

The single-parameter rule should only apply to unambiguous function
declarations. It never applies to function types. Function types should instead
infer a dependency on the closure context.

Fixes rdar://171031632 ([nonescapable] allow nonescaping closures to return
non-Escapable types)
atrick added a commit to atrick/swift that referenced this pull request Feb 25, 2026
@atrick
Fix lifetime type checking for nonescaping closures
cc7e4ab 
A nonescaping closure that returns a ~Escapable result and has no @_lifetime
annotation is assumed to depend on its closure context.

This fixes overly strict type checking introduced by:

    commit e98a7a6
    Date:   Fri Feb 6 02:09:25 2026
    Merge pull request swiftlang#86842
    LifetimeDependence: Support function types

Fix:

1. Disable missing dependency diagnostics for ~Escapable results

Continue allow the most basic nonescaping closure types without annotation:

    func f(body: () -> NE) -> NE

2. Disable single-parameter inference for function types

Do *not* infer a default parameter dependency here:

    func f(body: (AnyObject) -> NE) -> NE

The single-parameter rule should only apply to unambiguous function
declarations. It never applies to function types. Function types should instead
infer a dependency on the closure context.

Fixes rdar://171031632 ([nonescapable] allow nonescaping closures to return
non-Escapable types)
nickolas-pohilets pushed a commit to nickolas-pohilets/swift that referenced this pull request Mar 1, 2026
@atrick @nickolas-pohilets
Fix lifetime type checking for nonescaping closures
ede06e6 
A nonescaping closure that returns a ~Escapable result and has no @_lifetime
annotation is assumed to depend on its closure context.

This fixes overly strict type checking introduced by:

    commit e98a7a6
    Date:   Fri Feb 6 02:09:25 2026
    Merge pull request swiftlang#86842
    LifetimeDependence: Support function types

Fix:

1. Disable missing dependency diagnostics for ~Escapable results

Continue allow the most basic nonescaping closure types without annotation:

    func f(body: () -> NE) -> NE

2. Disable single-parameter inference for function types

Do *not* infer a default parameter dependency here:

    func f(body: (AnyObject) -> NE) -> NE

The single-parameter rule should only apply to unambiguous function
declarations. It never applies to function types. Function types should instead
infer a dependency on the closure context.

Fixes rdar://171031632 ([nonescapable] allow nonescaping closures to return
non-Escapable types)
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