[PATCH] D137415: [clang][Interp] Implement switch statements

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman accepted this revision.
aaron.ballman added inline comments.
This revision is now accepted and ready to land.


================
Comment at: clang/test/AST/Interp/switch.cpp:46
+constexpr int withInit() {
+  switch(int a = 2; a) {
+    case 1: return -1;
----------------
tbaeder wrote:
> aaron.ballman wrote:
> > I think it would be good to add a non-trivial init and show that it fails when appropriate. e.g.,
> > ```
> > struct Weirdo {
> >   consteval Weirdo(int);
> >   Weirdo(double);
> > 
> >   int Val = 1;
> > };
> > 
> > constexpr int whatever() {
> >   switch (Weirdo W(12); W.Val) {
> >   case 1: return 12;
> >   default: return 100;
> >   }
> > }
> > 
> > constexpr int whatever_else() {
> >   switch (Weirdo W(1.2); W.Val) { // Should get an error because of the init not being constexpr
> >   case 1: return 12;
> >   default: return 100;
> >   }
> > }
> > 
> > static_assert(whatever() == 12, "");
> > static_assert(whatever_else() == 12, ""); // Shouldn't compile because the function isn't constexpr
> > ```
> This is unfortunately hard do test with the new constant interpreter right now. It never emits the "never produces a constant expression" diagnostic because I removed the `Run()` call from `isPotentialConstantExpression()`. I need to revert that and instead fix the interpreter to correctly takes this mode into account.
> 
> And for the non-constexpr constructor, we will reject the call in the `static_assert()`, but not diagnose anything useful because we're not checking the constructor for constexpr-ness (this is part of https://reviews.llvm.org/D137563 I believe).
I'd be fine if the tests were added with FIXME comments (or commented out if they're too disruptive).


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D137415/new/

https://reviews.llvm.org/D137415