[PATCH] D76793: [Matrix] Implement + and - operators for MatrixType.

[John McCall via Phabricator via cfe-commits]

rjmccall added inline comments.


================
Comment at: clang/lib/Sema/SemaOverload.cpp:8587
+        if (S.Context.hasSameType(M1, M2))
+          AddCandidate(M1, M2);
+
----------------
I don't think this works if one side or the other has e.g. a templated conversion to a matrix type.  You need to add:

```
   (M1, M1) -> M1
   (M1, M1.ElementType) -> M1
   (M2, M2) -> M2    // but don't introduce the same candidate twice if the same type is also in the LHS set)
   (M2.ElementType, M2) -> M2
```

Test case is something like:

```
struct identmatrix_t {
  template <class T, unsigned N>
  operator matrix_type<T, N, N>() const {
    matrix_type<T, N, N> result = {};
    for (unsigned i = 0; i != N; ++i) result[i][i] = 1;
    return result;
  }
};
constexpr identmatrix_t identmatrix = identmatrix();

...
m + identmatrix
```

Also, these operator candidates are only for specific operators, right?  I think you can check what the operator is.


================
Comment at: clang/lib/Sema/SemaOverload.cpp:8593
+      AddCandidate(cast<MatrixType>(M2)->getElementType(), M2);
   }
 
----------------
Idiomatically, we just copy `QualType` instead of binding references to it.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D76793/new/

https://reviews.llvm.org/D76793