[PATCH] D146030: [clang][Interp] Handle LambdaExprs

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.


================
Comment at: clang/lib/AST/Interp/ByteCodeEmitter.cpp:56-57
+      const Record *R = P.getOrCreateRecord(MD->getParent());
+      llvm::DenseMap<const ValueDecl *, FieldDecl *> _LambdaCaptures;
+      FieldDecl *_LambdaThisCapture;
+
----------------
UB alert -- `_L` is reserved; let's pick names without leading underscores or shadowing.


================
Comment at: clang/lib/AST/Interp/ByteCodeEmitter.h:73-74
   llvm::DenseMap<const ParmVarDecl *, unsigned> Params;
+  /// Lambda captures.
+  llvm::DenseMap<const ValueDecl *, std::pair<unsigned, bool>> LambdaCaptures;
+  unsigned *LambdaThisCapture;
----------------
Can you add comments explaining what the `unsigned, bool` pair is encoding?


================
Comment at: clang/lib/AST/Interp/ByteCodeEmitter.h:75
+  llvm::DenseMap<const ValueDecl *, std::pair<unsigned, bool>> LambdaCaptures;
+  unsigned *LambdaThisCapture;
   /// Local descriptors.
----------------
Why is this a pointer? Since it's not really implemented, I'd recommend removing this for now and adding it back when you add support for capturing `this`.


================
Comment at: clang/test/AST/Interp/lambda.cpp:92
+  static_assert(foo() == 1); // expected-error {{not an integral constant expression}}
+}
+
----------------
How about some tests like:
```
constexpr int call_thru_func_ptr(int i) {
  auto l = [](int i) { return i; };
  int (*fp)(int) = l;
  return fp(i);  
}
static_assert(call_thru_func_ptr(12) == 12);

constexpr int call_through_copied_lambda(auto lam, int i) {
  auto copy = lam;
  return copy(i);
}

constexpr int call_through_copied_lambda(auto lam) {
  auto copy = lam;
  return copy();
}

void func() {
  constexpr int i = 12;
  static_assert(call_through_copied_lambda([i]() { return i; }) == 12);
}
```


Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D146030