[clang-tidy] Implement type-based check for `gsl::owner`

This check implements the typebased semantic of `gsl::owner`.
Meaning, that 
- only `gsl::owner` is allowed to get `delete`d
- `new` expression must be assigned to `gsl::owner`
- function calls that expect `gsl::owner` as argument, must get either an owner
  or a newly created and recognized resource (in the moment only `new`ed memory)
- assignment to `gsl::owner` must be either a resource or another owner
- functions returning an `gsl::owner` are considered as factories, and their result
  must be assigned to an `gsl::owner`
- classes that have an `gsl::owner`-member must declare a non-default destructor

There are some problems that occur when typededuction is in place.
For example `auto Var = function_that_returns_owner();` the type of `Var` will not be
an `gsl::owner`. This case is catched, and explicitly noted.

But cases like fully templated functions
```
template <typename T> 
void f(T t) { delete t; }
// ...
f(gsl::owner<int*>(new int(42)));
```
Will created false positive (the deletion is problematic), since the type deduction
removes the wrapping `typeAlias`.

Codereview in D36354



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@313067 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 0 deletions

diff --git a/clang-tidy/utils/Matchers.h b/clang-tidy/utils/Matchers.h
index adafdd9a..aeb639fa 100644
--- a/clang-tidy/utils/Matchers.h
+++ b/clang-tidy/utils/Matchers.h
@@ -17,6 +17,10 @@ namespace clang {
 namespace tidy {
 namespace matchers {
 
+AST_MATCHER(BinaryOperator, isAssignmentOperator) {
+  return Node.isAssignmentOp();
+}
+
 AST_MATCHER(BinaryOperator, isRelationalOperator) {
   return Node.isRelationalOp();
 }