CWG2672 Lambda body SFINAE is still required, contrary to intent and …

…note
tkoeppe · Dec 17, 2023 · Nov 13, 2023 · Nov 13, 2023 · Nov 13, 2023 · Nov 13, 2023
commit f303385d0dacfca64947a41e61122eedec11ae6a
diff --git a/source/expressions.tex b/source/expressions.tex
@@ -2871,8 +2871,10 @@
 
 \pnum
 The substitution of template arguments into a \grammarterm{requires-expression}
-may result in the formation of invalid types or expressions in its
-\grammarterm{requirement}s or the violation of the semantic constraints of those \grammarterm{requirement}s.
+can result in
+the formation of invalid types or expressions in the immediate context of
+its \grammarterm{requirement}s\iref{temp.deduct.general} or
+the violation of the semantic constraints of those \grammarterm{requirement}s.
 In such cases, the \grammarterm{requires-expression} evaluates to \keyword{false};
 it does not cause the program to be ill-formed.
 The substitution and semantic constraint checking

diff --git a/source/templates.tex b/source/templates.tex
@@ -1671,7 +1671,8 @@
 \defnx{satisfied}{constraint!satisfaction!atomic},
 the parameter mapping and template arguments are
 first substituted into its expression.
-If substitution results in an invalid type or expression,
+If substitution results in an invalid type or expression
+in the immediate context of the atomic constraint\iref{temp.deduct.general},
 the constraint is not satisfied.
 Otherwise, the lvalue-to-rvalue conversion\iref{conv.lval}
 is performed if necessary,
@@ -7266,9 +7267,8 @@
 \end{note}
 
 \pnum
-A \grammarterm{lambda-expression} appearing in a function type
-or a template parameter is not considered part of the immediate context
-for the purposes of template argument deduction.
+When substituting into a \grammarterm{lambda-expression},
+substitution into its body is not in the immediate context.
 \begin{note}
 The intent is to avoid requiring implementations to deal with
 substitution failure involving arbitrary statements.