[PATCH] [clang-tidy] Add a check for RAII temporaries.

[Daniel Jasper]

I think, this looks good as a first version.

As discussed offline, follow-ups could:
- Ignore objects that are known to have an empty destructor.
- Ignore constructors with more than one argument (reducing false positives at the cost of false negatives).
- Distinguish the case of attempted delegated constructors (consider adding a test now).

================
Comment at: clang-tidy/misc/UnusedRAII.cpp:53
@@ +52,3 @@
+  // statement.
+  const auto *CS = Result.Nodes.getStmtAs<CompoundStmt>("compound");
+  if (E == CS->body_back())
----------------
Add a test for this code path.

================
Comment at: clang-tidy/misc/UnusedRAII.cpp:72
@@ +71,3 @@
+    if (TOE->getNumArgs() == 0)
+      D << FixItHint::CreateRemoval(
+          CharSourceRange::getTokenRange(TOE->getParenOrBraceRange()));
----------------
Hm. Fix-It-wise, wouldn't it be better to create a single replacement instead of an insertion and a removal?

================
Comment at: clang-tidy/misc/UnusedRAII.h:36
@@ +35,3 @@
+///     to be RAII objects.
+///   - Ignore objects at the end of a compound statement (doesn't change behavior)
+///   - Ignore objects returned from a call.
----------------
nit: missing period at the end of the sentence.

http://reviews.llvm.org/D4615