[PATCH] D21187: Allow use of lambda expressions in array bounds

[Akira Hatanaka via cfe-commits]

ahatanak created this revision.
ahatanak added a subscriber: cfe-commits.

clang currently errors out when a lambda expression is used to compute the size of an array even though clang supports variable-length arrays as a C99 extension. For example,

$ cat vla1.cpp

```
int foo3();

struct S1 {
  virtual ~S1();
};

struct S2 : S1 {
};

void foo(S1 *s1) {
  unsigned char a1[([](int a) {return a; })(1)];
  unsigned char a2[foo3()]; // This is OK.
  unsigned char a3[!dynamic_cast<S2 *>(s1) + 1];  // This is OK.
}
```

$ clang++ vla1.cpp -c -std=c++11
vla1.cpp:11:21: error: a lambda expression may not appear inside of a constant expression
  unsigned char a1[([](int a) {return a; })(1)];
                    ^
1 error generated.

To handle VLAs in a more consistent way, this patch makes changes to allow lambda expressions to be used for array bounds if it is in a BlockContext.

http://reviews.llvm.org/D21187

Files:
  include/clang/Parse/Parser.h
  include/clang/Sema/Sema.h
  lib/Parse/ParseDecl.cpp
  lib/Parse/ParseExpr.cpp
  lib/Sema/Sema.cpp
  lib/Sema/SemaExpr.cpp
  test/SemaCXX/lambda-expressions.cpp

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