[stdlib] document compatibility entry point silgen names better

Author: glessard

stdlib/public/core/UnsafeBufferPointer.swift.gyb

@@ -763,8 +763,9 @@ extension Unsafe${Mutable}BufferPointer {
   }
 
   // This unavailable implementation uses the expected mangled name
-  // of `withMemoryRebound`, and provides an entry point for any
-  // binary compiled against the stlib binary for Swift 5.6 and older.
+  // of `withMemoryRebound<T, Result>(to:_:)`, and provides
+  // an entry point for any binary linked against the stlib binary
+  // for Swift 5.6 and older.
   @available(*, unavailable)
 % if Mutable:
   @_silgen_name("$sSr17withMemoryRebound2to_qd_0_qd__m_qd_0_Sryqd__GKXEtKr0_lF")

stdlib/public/core/UnsafePointer.swift

@@ -326,8 +326,9 @@ public struct UnsafePointer<Pointee>: _Pointer {
   }
 
   // This unavailable implementation uses the expected mangled name
-  // of `withMemoryRebound`, and provides an entry point for any
-  // binary compiled against the stlib binary for Swift 5.6 and older.
+  // of `withMemoryRebound<T, Result>(to:capacity:_:)`, and provides
+  // an entry point for any binary linked against the stlib binary
+  // for Swift 5.6 and older.
   @available(*, unavailable)
   @_silgen_name("$sSP17withMemoryRebound2to8capacity_qd_0_qd__m_Siqd_0_SPyqd__GKXEtKr0_lF")
   @usableFromInline
@@ -1032,8 +1033,9 @@ public struct UnsafeMutablePointer<Pointee>: _Pointer {
   }
 
   // This unavailable implementation uses the expected mangled name
-  // of `withMemoryRebound`, and provides an entry point for any
-  // binary compiled against the stlib binary for Swift 5.6 and older.
+  // of `withMemoryRebound<T, Result>(to:capacity:_:)`, and provides
+  // an entry point for any binary linked against the stlib binary
+  // for Swift 5.6 and older.
   @available(*, unavailable)
   @_silgen_name("$sSp17withMemoryRebound2to8capacity_qd_0_qd__m_Siqd_0_Spyqd__GKXEtKr0_lF")
   @usableFromInline

stdlib/public/core/UnsafeRawBufferPointer.swift.gyb

@@ -480,7 +480,7 @@ extension Unsafe${Mutable}RawBufferPointer {
 
   // This unavailable implementation uses the expected mangled name
   // of `storeBytes<T>(of:toByteOffset:as:)`, and provides an entry point for
-  // any binary compiled against the stlib binary for Swift 5.6 and older.
+  // any binary linked against the stlib binary for Swift 5.6 and older.
   @available(*, unavailable)
   @_silgen_name("$sSw10storeBytes2of12toByteOffset2asyx_SixmtlF")
   @usableFromInline func _legacy_se0349_storeBytes<T>(