An unevaluated operand is not evaluated. An unevaluated operand is considered a full-expression. Let’s look at these in detail. I will use the following declarations in my examples. The declared functions are never defined anywhere so if a call to them appears in an evaluated context, the program is ill-formed and we will get a link-time error. Calling them in an unevaluated context is fine, however.
Move lambda out of unevaluated context #1230. Merged 4 of 4 tasks complete. Copy link Quote reply Contributor Author mandreyel commented Sep 10, 2018. Made the changes in #1230! nlohmann closed this in #1230 Sep 10, 2018. nlohmann self-assigned this Sep 10, 2018. nlohmann added this to …
Yes. From [temp.constr.expr], wording as of N4641:. An expression constraint is a constraint that specifies a requirement on the formation of an expression E through substitution of template arguments. An expression constraint is satisfied if substitution yielding E did not fail.Within an expression constraint, E is an unevaluated operand (Clause 5). So using declval should be fine.
Coverage remained the same at 100.0% when pulling 6b5334c on mandreyel:lambda- unevaluated-context -fix into ebb3c03 on nlohmann:develop. nlohmann requested changes.
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12/15/2020 · captures – a comma-separated list of zero or more captures, optionally beginning with a capture-default.. See below for the detailed description of captures.. A lambda expression can use a variable without capturing it if the variable is a non-local variable or has static or thread local storage duration (in which case the variable cannot be captured), or, 8/7/2020 · Unevaluated Context. The following code snippet has a function declaration and a function definition. int add1 ( int, int ); // declaration int add2 ( int a, int b) { return a + b; } // definition. add1 declares a function, but add2 defines it.
12/17/2020 · the expression is well-formed in unevaluated context where INVOKE (f, t1, t2, …
tN) is defined as static_cast ( INVOKE ( f, t1, t2, …
tN ) ) if R is possibly cv-qualified void , otherwise, INVOKE(f, t1, t2, …
tN) is implicitly converted to R, An unevaluated operand is not evaluated. [ Note 1 : In an unevaluated operand, a non-static class member can be named ( [expr. prim. id] ) and naming of objects or functions does not, by itself, require that a definition be provided ( [basic. def. odr] ) .
