royjacobson added inline comments.
================
Comment at: clang/include/clang/Basic/DiagnosticParseKinds.td:1037-1041
+def err_static_mutable_lambda : Error<
+ "lambda cannot be both mutable and static">;
+def err_static_lambda_captures : Error<
+ "a static lambda cannot have any captures">;
+def note_lambda_captures : Note<"captures declared here">;
----------------
aaron.ballman wrote:
> These are semantic errors, not parsing ones. This means these will be
> diagnosed when parsing the lambda rather than when instantiating it. I don't
> think that matters for the cast of combining `mutable` and `static`, but I'm
> less certain about "have any captures" because of cases like:
> ```
> template <typename... Types>
> auto func(Types... Ts) {
> return [Ts...] { return 1; };
> }
>
> int main() {
> auto lambda = func();
> }
> ```
> I'm pretty sure that lambda has no captures for that call, but it could have
> captures depending on the instantiation.
>
> Actually, from some off-list discussion with @erichkeane, even mutable and
> static are a problem in code like:
> ```
> template <typename Ty>
> void func(T t) {
> if constexpr (Something<T>) {
> [](){};
> } else {
> [t](){};
> }
> ```
> where the lambda is in a discarded statement.
>
> So I think these might need to change to be Sema diagnostics (and we should
> add some additional test coverage).
From https://eel.is/c++draft/expr.prim.lambda.general#4
> If the lambda-specifier-seq contains static, there shall be no lambda-capture
So this should be a parsing error. Or maybe I don't understand what you're
saying. There are no static lambdas in your examples so I'm not sure how
they're related.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D133659/new/
https://reviews.llvm.org/D133659
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