Recommit "[AST] Factor out the logic of the various Expr::Ignore*"

(Originally commited in r354215 and reverted in r354216 because of a
 missed failing clang-tidy test (fix in r354228))

Now that the implementation of all of the Expr::Ignore* is in Expr.cpp
we can try to remove some duplication. Do this by separating the logic
of the Expr::Ignore* from the iterative loop.

This is NFC, except for one change: IgnoreParenImpCasts now skips,
among other things, everything that IgnoreImpCasts skips. This means
FullExpr are now skipped by IgnoreParenImpCasts. This was likely an
oversight when FullExpr was added to the nodes skipped by IgnoreImpCasts.

Differential Revision: https://reviews.llvm.org/D57267

Reviewed By: aaron.ballman (with comments from void and rnk)

llvm-svn: 354232

0 files changed, 0 insertions, 0 deletions