Rename _unsafeLifetime to @unsafe _overrideLifetime and reformat.

Also, fix the _overrideLifetime doc comments.

Author: atrick

stdlib/public/core/LifetimeManager.swift

@@ -286,37 +286,36 @@ public func _copy<T>(_ value: T) -> T {
 
 /// Unsafely discard any lifetime dependency on the `dependent` argument. Return
 /// a value identical to `dependent` with a lifetime dependency on the caller's
-/// borrow scope of the `borrows` argument.
-///
-/// TODO: Remove @_unsafeNonescapableResult. Instead, the unsafe dependence
-/// should be expressed by a builtin that is hidden within the function body.
+/// borrow scope of the `source` argument.
+@unsafe
 @_unsafeNonescapableResult
 @_alwaysEmitIntoClient
 @inline(__always)
 @lifetime(borrow source)
-internal func _unsafeLifetime<T: ~Copyable & ~Escapable,
-                              U: ~Copyable & ~Escapable>(
-  dependent: consuming T, borrows source: borrowing U
+internal func _overrideLifetime<
+  T: ~Copyable & ~Escapable, U: ~Copyable & ~Escapable
+>(
+  _ dependent: consuming T, borrowing source: borrowing U
 ) -> T {
+  // TODO: Remove @_unsafeNonescapableResult. Instead, the unsafe dependence
+  // should be expressed by a builtin that is hidden within the function body.
   dependent
 }
 
 /// Unsafely discard any lifetime dependency on the `dependent` argument. Return
 /// a value identical to `dependent` that inherits all lifetime dependencies from
-/// the `dependsOn` argument.
-///
-/// Transferring generic lifetime dependencies from `dependsOn` requires the
-/// result to have the same type.
-///
-/// TODO: Remove @_unsafeNonescapableResult. Instead, the unsafe dependence
-/// should be expressed by a builtin that is hidden within the function body.
+/// the `source` argument.
+@unsafe
 @_unsafeNonescapableResult
 @_alwaysEmitIntoClient
 @inline(__always)
 @lifetime(source)
-internal func _unsafeLifetime<T: ~Copyable & ~Escapable,
-                              U: ~Copyable & ~Escapable>(
-  dependent: consuming T, dependsOn source: borrowing U
+internal func _overrideLifetime<
+  T: ~Copyable & ~Escapable, U: ~Copyable & ~Escapable
+>(
+  _ dependent: consuming T, copying source: borrowing U
 ) -> T {
+  // TODO: Remove @_unsafeNonescapableResult. Instead, the unsafe dependence
+  // should be expressed by a builtin that is hidden within the function body.
   dependent
 }

stdlib/public/core/Span/RawSpan.swift

@@ -101,7 +101,7 @@ extension RawSpan {
     let span = RawSpan(_unchecked: baseAddress, byteCount: buffer.count)
     // As a trivial value, 'baseAddress' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 
   /// Unsafely create a `RawSpan` over initialized memory.
@@ -121,7 +121,7 @@ extension RawSpan {
     let span = RawSpan(_unsafeBytes: rawBuffer)
     // As a trivial value, 'rawBuffer' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 
   /// Unsafely create a `RawSpan` over initialized memory.
@@ -141,7 +141,7 @@ extension RawSpan {
     let span = RawSpan(_unsafeBytes: rawBuffer)
     // As a trivial value, 'rawBuffer' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 
   @_alwaysEmitIntoClient
@@ -154,7 +154,7 @@ extension RawSpan {
     let span = RawSpan(_unsafeBytes: rawBuffer)
     // As a trivial value, 'rawBuffer' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 
   /// Unsafely create a `RawSpan` over initialized memory.
@@ -194,7 +194,7 @@ extension RawSpan {
     let span = RawSpan(_unsafeBytes: rawBuffer)
     // As a trivial value, 'rawBuffer' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 
   /// Unsafely create a `RawSpan` over initialized memory.
@@ -214,7 +214,7 @@ extension RawSpan {
     let span = RawSpan(_unsafeBytes: rawBuffer)
     // As a trivial value, 'rawBuffer' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 
   /// Unsafely create a `RawSpan` over initialized memory.
@@ -234,7 +234,7 @@ extension RawSpan {
     let span = RawSpan(_unsafeBytes: rawBuffer)
     // As a trivial value, 'rawBuffer' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 
   /// Unsafely create a `RawSpan` over initialized memory.
@@ -255,7 +255,7 @@ extension RawSpan {
     let span = RawSpan(_unsafeBytes: rawBuffer)
     // As a trivial value, 'rawBuffer' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 
   /// Unsafely create a `RawSpan` over initialized memory.
@@ -374,7 +374,7 @@ extension RawSpan {
   public func _extracting(unchecked bounds: Range<Int>) -> Self {
     let newStart = _pointer?.advanced(by: bounds.lowerBound)
     let newSpan = RawSpan(_unchecked: newStart, byteCount: bounds.count)
-    return _unsafeLifetime(dependent: newSpan, dependsOn: self)
+    return _overrideLifetime(newSpan, copying: self)
   }
 
   /// Constructs a new span over the bytes within the supplied range of
@@ -488,7 +488,7 @@ extension RawSpan {
     let newSpan = Span<T>(_unsafeBytes: rawBuffer)
     // As a trivial value, 'rawBuffer' does not formally depend on the
     // lifetime of 'self'. Make the dependence explicit.
-    return _unsafeLifetime(dependent: newSpan, dependsOn: self)
+    return _overrideLifetime(newSpan, copying: self)
   }
 }
 
@@ -711,7 +711,7 @@ extension RawSpan {
     let newSpan = RawSpan(_unchecked: newStart, byteCount: newCount)
     // As a trivial value, 'newStart' does not formally depend on the
     // lifetime of 'self'. Make the dependence explicit.
-    return _unsafeLifetime(dependent: newSpan, dependsOn: self)
+    return _overrideLifetime(newSpan, copying: self)
   }
 
   /// Returns a span over all but the given number of initial bytes.
@@ -737,6 +737,6 @@ extension RawSpan {
     let newSpan = RawSpan(_unchecked: newStart, byteCount: byteCount &- droppedCount)
     // As a trivial value, 'newStart' does not formally depend on the
     // lifetime of 'self'. Make the dependence explicit.
-    return _unsafeLifetime(dependent: newSpan, dependsOn: self)
+    return _overrideLifetime(newSpan, copying: self)
   }
 }

stdlib/public/core/Span/Span.swift

@@ -109,7 +109,7 @@ extension Span where Element: ~Copyable {
     let span = Span(_unchecked: baseAddress, count: buffer.count)
     // As a trivial value, 'baseAddress' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 
   /// Unsafely create a `Span` over initialized memory.
@@ -129,7 +129,7 @@ extension Span where Element: ~Copyable {
     let span = Span(_unsafeElements: buf)
     // As a trivial value, 'buf' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 
   /// Unsafely create a `Span` over initialized memory.
@@ -153,7 +153,7 @@ extension Span where Element: ~Copyable {
     let span = Span(_unsafeElements: buf)
     // As a trivial value, 'buf' does not formally depend on the
     // lifetime of 'pointer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: pointer)
+    self = _overrideLifetime(span, borrowing: pointer)
   }
 }
 
@@ -177,7 +177,7 @@ extension Span {
     let span = Span(_unsafeElements: buf)
     // As a trivial value, 'buf' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 
   /// Unsafely create a `Span` over initialized memory.
@@ -197,7 +197,7 @@ extension Span {
     let span = Span(_unsafeElements: buf)
     // As a trivial value, 'buf' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 }
 
@@ -236,7 +236,7 @@ extension Span where Element: BitwiseCopyable {
     let span = Span(_unchecked: baseAddress, count: count)
     // As a trivial value, 'baseAddress' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 
   /// Unsafely create a `Span` over initialized memory.
@@ -260,7 +260,7 @@ extension Span where Element: BitwiseCopyable {
     let span = Span(_unsafeBytes: rawBuffer)
     // As a trivial value, 'buf' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 
   /// Unsafely create a `Span` over initialized memory.
@@ -288,7 +288,7 @@ extension Span where Element: BitwiseCopyable {
     let span = Span(_unsafeBytes: rawBuffer)
     // As a trivial value, 'rawBuffer' does not formally depend on the
     // lifetime of 'pointer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: pointer)
+    self = _overrideLifetime(span, borrowing: pointer)
   }
 
   /// Unsafely create a `Span` over initialized memory.
@@ -312,7 +312,7 @@ extension Span where Element: BitwiseCopyable {
     let span = Span(_unsafeBytes: rawBuffer)
     // As a trivial value, 'rawBuffer' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 
   /// Unsafely create a `Span` over initialized memory.
@@ -336,7 +336,7 @@ extension Span where Element: BitwiseCopyable {
     let span = Span(_unsafeBytes: rawBuffer)
     // As a trivial value, 'rawBuffer' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, borrows: buffer)
+    self = _overrideLifetime(span, borrowing: buffer)
   }
 
   /// Create a `Span` over the bytes represented by a `RawSpan`
@@ -352,7 +352,7 @@ extension Span where Element: BitwiseCopyable {
     let span = Span(_unsafeBytes: rawBuffer)
     // As a trivial value, 'rawBuffer' does not formally depend on the
     // lifetime of 'bytes'. Make the dependence explicit.
-    self = _unsafeLifetime(dependent: span, dependsOn: bytes)
+    self = _overrideLifetime(span, copying: bytes)
   }
 }
 
@@ -526,7 +526,7 @@ extension Span where Element: ~Copyable {
     let newSpan = Span(_unchecked: newStart, count: bounds.count)
     // As a trivial value, 'newStart' does not formally depend on the
     // lifetime of 'self'. Make the dependence explicit.
-    return _unsafeLifetime(dependent: newSpan, dependsOn: self)
+    return _overrideLifetime(newSpan, copying: self)
   }
 
   /// Constructs a new span over the items within the supplied range of
@@ -752,7 +752,7 @@ extension Span where Element: ~Copyable {
     let newSpan = Span(_unchecked: newStart, count: newCount)
     // As a trivial value, 'newStart' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    return _unsafeLifetime(dependent: newSpan, dependsOn: self)
+    return _overrideLifetime(newSpan, copying: self)
   }
 
   /// Returns a span over all but the given number of initial elements.
@@ -779,6 +779,6 @@ extension Span where Element: ~Copyable {
     let newSpan = Span(_unchecked: newStart, count: count &- droppedCount)
     // As a trivial value, 'newStart' does not formally depend on the
     // lifetime of 'buffer'. Make the dependence explicit.
-    return _unsafeLifetime(dependent: newSpan, dependsOn: self)
+    return _overrideLifetime(newSpan, copying: self)
   }
 }