================
@@ -1361,6 +1367,20 @@ class Sema final {
// VLAs).
bool InConditionallyConstantEvaluateContext = false;
+ /// Whether we are currently in a context in which all temporaries must be
+ /// lifetime-extended, even if they're not bound to a reference (for
example,
+ /// in a for-range initializer).
+ bool IsInLifetimeExtendingContext = false;
+
+ /// Whether we should materialize temporaries in discarded expressions.
+ ///
+ /// [C++23][class.temporary]/p2.6 when a prvalue that has type other than
cv
+ /// void appears as a discarded-value expression ([expr.context]).
+ ///
+ /// We do not materialize temporaries by default in order to avoid creating
+ /// unnecessary temporary objects.
+ bool MaterializePRValueInDiscardedExpression = false;
----------------
yronglin wrote:
I think this variable and related function
`needMaterializePRValueInDiscardedExpression()` should be renamed to
`NeedMaterializePRValue` and `needMaterializePRValue()` , then it can use in
other cases.
In [class.temporary P2][http://eel.is/c++draft/class.temporary#2]
The materialization of a temporary object is generally delayed as long as
possible in order to avoid creating unnecessary temporary
objects[.](http://eel.is/c++draft/class.temporary#2.sentence-1)
[Note [3](http://eel.is/c++draft/class.temporary#note-3): Temporary objects are
materialized:
[(2.1)](http://eel.is/c++draft/class.temporary#2.1)
when binding a reference to a prvalue
([[dcl.init.ref]](http://eel.is/c++draft/dcl.init.ref),
[[expr.type.conv]](http://eel.is/c++draft/expr.type.conv),
[[expr.dynamic.cast]](http://eel.is/c++draft/expr.dynamic.cast),
[[expr.static.cast]](http://eel.is/c++draft/expr.static.cast),
[[expr.const.cast]](http://eel.is/c++draft/expr.const.cast),
[[expr.cast]](http://eel.is/c++draft/expr.cast)),
[(2.2)](http://eel.is/c++draft/class.temporary#2.2)
when performing member access on a class prvalue
([[expr.ref]](http://eel.is/c++draft/expr.ref),
[[expr.mptr.oper]](http://eel.is/c++draft/expr.mptr.oper)),
[(2.3)](http://eel.is/c++draft/class.temporary#2.3)
when performing an array-to-pointer conversion or subscripting on an array
prvalue ([[conv.array]](http://eel.is/c++draft/conv.array),
[[expr.sub]](http://eel.is/c++draft/expr.sub)),
[(2.4)](http://eel.is/c++draft/class.temporary#2.4)
when initializing an object of type std::initializer_list<T> from a
[braced-init-list](http://eel.is/c++draft/dcl.init.general#nt:braced-init-list)
([[dcl.init.list]](http://eel.is/c++draft/dcl.init.list)),
[(2.5)](http://eel.is/c++draft/class.temporary#2.5)
for certain unevaluated operands
([[expr.typeid]](http://eel.is/c++draft/expr.typeid),
[[expr.sizeof]](http://eel.is/c++draft/expr.sizeof)), and
[(2.6)](http://eel.is/c++draft/class.temporary#2.6)
when a prvalue that has type other than cv void appears as a discarded-value
expression
([[expr.context]](http://eel.is/c++draft/expr.context))[.](http://eel.is/c++draft/class.temporary#2.sentence-2)
— end note]
https://github.com/llvm/llvm-project/pull/76361
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