[clang-tools-extra] [clang-tidy] Added bugprone-exception-rethrow check (PR #86448)

[via cfe-commits]

================
@@ -0,0 +1,60 @@
+// RUN: %check_clang_tidy %s bugprone-exception-rethrow %t -- -- -fexceptions
+
+struct exception {};
+
+void correct() {
+  try {
+      throw exception();
+  } catch(const exception &) {
+      throw;
+  }
+}
+
+void correct2() {
+  try {
+      throw exception();
+  } catch(const exception &e) {
+      try {
+        throw exception();
+      } catch(...) {}
+  }
+}
+
+void not_correct() {
+  try {
+      throw exception();
+  } catch(const exception &e) {
+      throw e;
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: throwing a copy of the caught 'exception' exception, remove the argument to throw the original exception object [bugprone-exception-rethrow]
+  }
+}
+
+void not_correct2() {
+  try {
+      throw 5;
+  } catch(const int &e) {
+      throw e;
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: throwing a copy of the caught 'int' exception, remove the argument to throw the original exception object [bugprone-exception-rethrow]
+  }
+}
+
+void rethrow_not_correct() {
+  throw;
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: empty 'throw' outside a catch block without an exception can trigger 'std::terminate' [bugprone-exception-rethrow]
+}
+
+void rethrow_not_correct2() {
+  try {
+    throw;
+// CHECK-MESSAGES: :[[@LINE-1]]:5: warning: empty 'throw' outside a catch block without an exception can trigger 'std::terminate' [bugprone-exception-rethrow]
+  } catch(...) {
+  }
+}
+
+void rethrow_correct() {
+  try {
+    throw 5;
+  } catch(...) {
+    throw;
+  }
+}
----------------
isuckatcs wrote:

Also the `optionally(hasAncestor(cxxCatchStmt().bind("catch")))` matcher allows escaping `throw;` statements to slip through the check. This could also be documented as a limitation.

E.g.:
```c++
void foo() {
  std::function<void()> fn;

  try {
    throw 1;
  } catch (...) {
    fn = [] { throw; };
  }

  fn();
}
``` 

https://github.com/llvm/llvm-project/pull/86448