[AST] Update the comments of the various Expr::Ignore* + Related cleanups

The description of what the various Expr::Ignore* do has drifted from the
actual implementation.

Inspection reveals that IgnoreParenImpCasts() is not equivalent to doing
IgnoreParens() + IgnoreImpCasts() until reaching a fixed point, but
IgnoreParenCasts() is equivalent to doing IgnoreParens() + IgnoreCasts()
until reaching a fixed point. There is also a fair amount of duplication
in the various Expr::Ignore* functions which increase the chance of further
future inconsistencies. In preparation for the next patch which will factor
out the implementation of the various Expr::Ignore*, do the following cleanups:

Remove Stmt::IgnoreImplicit, in favor of Expr::IgnoreImplicit. IgnoreImplicit
is the only function among all of the Expr::Ignore* which is available in Stmt.
There are only a few users of Stmt::IgnoreImplicit. They can just use instead
Expr::IgnoreImplicit like they have to do for the other Ignore*.

Move Expr::IgnoreImpCasts() from Expr.h to Expr.cpp. This made no difference
in the run-time with my usual benchmark (-fsyntax-only on all of Boost).

While we are at it, make IgnoreParenNoopCasts take a const reference to the
ASTContext for const correctness.

Update the comments to match what the Expr::Ignore* are actually doing.
I am not sure that listing exactly what each Expr::Ignore* do is optimal,
but it certainly looks better than the current state which is in my opinion
between misleading and just plain wrong.

The whole patch is NFC (if you count removing Stmt::IgnoreImplicit as NFC).

Differential Revision: https://reviews.llvm.org/D57266

Reviewed By: aaron.ballman

llvm-svn: 353006

1 files changed, 0 insertions, 24 deletions

diff --git a/clang/lib/AST/Stmt.cpp b/clang/lib/AST/Stmt.cpp
index e1a4dfc10e1..d1a4dc074bd 100644
--- a/clang/lib/AST/Stmt.cpp
+++ b/clang/lib/AST/Stmt.cpp
@@ -117,30 +117,6 @@ void Stmt::EnableStatistics() {
   StatisticsEnabled = true;
 }
 
-Stmt *Stmt::IgnoreImplicit() {
-  Stmt *s = this;
-
-  Stmt *lasts = nullptr;
-
-  while (s != lasts) {
-    lasts = s;
-
-    if (auto *fe = dyn_cast<FullExpr>(s))
-      s = fe->getSubExpr();
-
-    if (auto *mte = dyn_cast<MaterializeTemporaryExpr>(s))
-      s = mte->GetTemporaryExpr();
-
-    if (auto *bte = dyn_cast<CXXBindTemporaryExpr>(s))
-      s = bte->getSubExpr();
-
-    if (auto *ice = dyn_cast<ImplicitCastExpr>(s))
-      s = ice->getSubExpr();
-  }
-
-  return s;
-}
-
 /// Skip no-op (attributed, compound) container stmts and skip captured
 /// stmt at the top, if \a IgnoreCaptured is true.
 Stmt *Stmt::IgnoreContainers(bool IgnoreCaptured) {