[SR-14443] [C++] Don't crash on invalid dependent values.

[zoecarver]

Previous ID	SR-14443
Radar	rdar://problem/83367285
Original Reporter	@zoecarver
Type	Bug

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, CxxInterop, StarterBug
Assignee	Rajagopalan (JIRA)
Priority	Medium

md5: f34665bb62c6ff5d157cb3bd483d8006

Issue Description:

A while theindigamer (JIRA User) found this compiler crasher and I never got around to fixing it or creating a bug for it.

struct S {};
template <class T>
 struct IsSubtypeSame {
   static constexpr const S value = T();
};

using Invalid = IsSubtypeSame<int>;

[zoecarver]

thomassw66 (JIRA User) this might be another interesting one to look at. It should just be a matter of finding the condition that causes this crash and then bailing on it.

[swift-ci]

Comment by Rajagopalan Gangadharan (JIRA)

@zoecarver theindigamer (JIRA User) I would like to work on this, is there any details that I might find useful. Please do drop a comment. Thank you!

[swift-ci]

Comment by Rajagopalan Gangadharan (JIRA)

Upon executing this I was not able to crash the compiler Instead I got a bunch of errors. Does this example needs some tweaking?

crash.swift:2:9: error: consecutive statements on a line must be separated by ';'
template <class T>
        ^
        ;
crash.swift:2:11: error: expected expression
template <class T>
          ^
crash.swift:2:18: error: expected '{' in class
template <class T>
                 ^
crash.swift:4:11: error: expected 'func' keyword in static method declaration
   static constexpr const S value = T();
          ^
          func
crash.swift:4:21: error: found an unexpected second identifier in function declaration; is there an accidental break?
   static constexpr const S value = T();
                    ^
crash.swift:4:21: note: join the identifiers together
   static constexpr const S value = T();
          ~~~~~~~~~~^~~~~
          constexprconst
crash.swift:4:21: note: join the identifiers together with camel-case
   static constexpr const S value = T();
          ~~~~~~~~~~^~~~~
          constexprConst
crash.swift:4:27: error: expected '(' in argument list of function declaration
   static constexpr const S value = T();
                          ^
crash.swift:4:26: error: consecutive declarations on a line must be separated by ';'
   static constexpr const S value = T();
                         ^
                         ;
crash.swift:4:27: error: expected declaration
   static constexpr const S value = T();
                          ^
crash.swift:3:9: note: in declaration of 'IsSubtypeSame'
 struct IsSubtypeSame {
        ^
crash.swift:7:6: error: consecutive statements on a line must be separated by ';'
using Invalid = IsSubtypeSame<int>;
     ^
     ;
crash.swift:2:1: error: cannot find 'template' in scope
template <class T>
^~~~~~~~
crash.swift:4:11: error: expected '{' in body of function declaration
   static constexpr const S value = T();
          ^
crash.swift:7:1: error: cannot find 'using' in scope
using Invalid = IsSubtypeSame<int>;
^~~~~
crash.swift:7:7: error: cannot find 'Invalid' in scope
using Invalid = IsSubtypeSame<int>;
      ^~~~~~~

[zoecarver]

Hey Rajagopalan (JIRA User)! Happy to have you work on this. Feel free to reach out to me if you get stuck or want some help.

> Upon executing this I was not able to crash the compiler Instead I got a bunch of errors. Does this example needs some tweaking?

Is it possible that you're putting the C++ code in a Swift file? If so, what you are going to need to do is create a C++ header file and a module map. Then `import Test` the C++ module. You can see an example of this in the `swift/test/Interop/Cxx/namespace` where we have the C++ headers in `namespace/Inputs/<>.h`, the module map in `namespace/Inputs/module.modulemap`, and the Swift files in `namespace/<>.swift`.

[swift-ci]

Comment by Rajagopalan Gangadharan (JIRA)

@zoecarver Thank you for correcting my stupid mistake 😛. Will do this and let you know how this goes.

[zoecarver]

@swift-ci create