From c87116b33267a8df388ca3652d211b7f8254a98d Mon Sep 17 00:00:00 2001
From: Moonchild <moonchild@palemoon.org>
Date: Wed, 18 Oct 2023 14:35:59 +0200
Subject: Issue #2281 - Add some deduction guides for class template arguments.

This is necessary if we want to start using Span() constructors
instead of the MakeSpan() kludge.
---
 mfbt/Span.h           | 9 +++++++++
 xpcom/glue/nsTArray.h | 6 ++++++
 2 files changed, 15 insertions(+)

diff --git a/mfbt/Span.h b/mfbt/Span.h
index e71e068c60..fe679aa8bf 100644
--- a/mfbt/Span.h
+++ b/mfbt/Span.h
@@ -810,6 +810,15 @@ private:
   storage_type<span_details::extent_type<Extent>> storage_;
 };
 
+template <typename T, size_t Extent>
+Span(T (&aArr)[Extent]) -> Span<T, Extent>;
+
+template <class Container>
+Span(Container&) -> Span<typename Container::value_type>;
+
+template <class Container>
+Span(const Container&) -> Span<const typename Container::value_type>;
+
 // [Span.comparison], Span comparison operators
 template<class ElementType, size_t FirstExtent, size_t SecondExtent>
 inline bool
diff --git a/xpcom/glue/nsTArray.h b/xpcom/glue/nsTArray.h
index 03913a3765..47635de318 100644
--- a/xpcom/glue/nsTArray.h
+++ b/xpcom/glue/nsTArray.h
@@ -2466,6 +2466,12 @@ MakeSpan(const nsTArray_Impl<ElementType, TArrayAlloc>& aTArray)
   return aTArray;
 }
 
+template <typename E, class Alloc>
+Span(nsTArray_Impl<E, Alloc>&) -> Span<E>;
+
+template <typename E, class Alloc>
+Span(const nsTArray_Impl<E, Alloc>&) -> Span<const E>;
+
 } // namespace mozilla
 
 // Assert that AutoTArray doesn't have any extra padding inside.
-- 
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