P0806R2 Deprecate implicit capture of this via [=]

Author: tkoeppe

source/expressions.tex

@@ -1392,6 +1392,8 @@
 the entity is said to be \defnx{implicitly captured}{capture!implicit}
 by each intervening \grammarterm{lambda-expression} with an associated
 \grammarterm{capture-default} that does not explicitly capture it.
+The implicit capture of \tcode{*this} is deprecated when the
+\grammarterm{capture-default} is \tcode{=}; see \ref{depr.capture.this}.
 \begin{example}
 \begin{codeblock}
 void f(int, const int (&)[2] = {});         // \#1

source/future.tex

@@ -48,6 +48,25 @@
 \pnum
 The \grammarterm{noexcept-specifier} \tcode{throw()} is deprecated.
 
+\rSec1[depr.capture.this]{Implicit capture of \tcode{*this} by reference}
+
+\pnum
+For compatibility with prior \Cpp{} International Standards,
+a lambda expression with \grammarterm{capture-default}
+\tcode{=}\iref{expr.prim.lambda.capture} can implicitly capture
+\tcode{*this} by reference.
+\begin{example}
+\begin{codeblock}
+struct X {
+  int x;
+  void foo(int n) {
+    auto f = [=]() { x = n; };          // deprecated: \tcode{x} means \tcode{this->x}, not a copy thereof
+    auto g = [=, this]() { x = n; };    // recommended replacement
+  }
+};
+\end{codeblock}
+\end{example}
+
 \rSec1[depr.cpp.headers]{\Cpp{} standard library headers}
 
 \pnum