Fix crash when accessing span of empty InlineArray (#85268)

Fix crash when creating a Span from an empty InlineArray whose storage
is only byte-aligned. #85265.

---------

Co-authored-by: Guillaume Lessard <glessard@tffenterprises.com>

Author: jairajput

stdlib/public/core/InlineArray.swift

@@ -587,6 +587,10 @@ extension InlineArray where Element: ~Copyable {
     @lifetime(borrow self)
     @_transparent
     borrowing get {
+      guard count > 0 else {
+        let span = Span<Element>()
+        return unsafe _overrideLifetime(span, borrowing: self)
+      }
       let span = unsafe Span(_unsafeStart: _protectedAddress, count: count)
       return unsafe _overrideLifetime(span, borrowing: self)
     }
@@ -598,6 +602,10 @@ extension InlineArray where Element: ~Copyable {
     @lifetime(&self)
     @_transparent
     mutating get {
+      guard count > 0 else {
+        let span = MutableSpan<Element>()
+        return unsafe _overrideLifetime(span, mutating: &self)
+      }
       let span = unsafe MutableSpan(
         _unsafeStart: _protectedMutableAddress,
         count: count

test/stdlib/Span/InlineSpanProperties.swift

@@ -119,6 +119,16 @@ suite.test("InlineArray.span property (String)")
   }    
 }
 
+suite.test("InlineArray.span property (empty, aligned)")
+.require(.stdlib_6_2).code {
+  guard #available(SwiftStdlib 6.2, *) else { return }
+
+  let empty: InlineArray<0, Padded> = []
+  let span = empty.span
+  expectTrue(span.isEmpty)
+  expectEqual(span.count, 0)
+}
+
 suite.test("InlineArray.mutableSpan property")
 .require(.stdlib_6_2).code
 {
@@ -146,3 +156,14 @@ suite.test("InlineArray.mutableSpan property (String)")
   let s = span[3]
   expectTrue(s._isIdentical(to: v[3]))
 }
+
+suite.test("InlineArray.mutableSpan property (empty, aligned)")
+.require(.stdlib_6_2).code
+{
+  guard #available(SwiftStdlib 6.2, *) else { return }
+
+  var empty: InlineArray<0, Padded> = []
+  var span = empty.mutableSpan
+  expectTrue(span.isEmpty)
+  expectEqual(span.count, 0)
+}