tree eb234612ef1a0f6f7721bb84dd45230ae75b1b0e
parent a3306f0b9f988677bf12c3403dd0c0336cb5c246
author Eli Friedman <eli.friedman@gmail.com> 1242655012 +0000
committer Eli Friedman <eli.friedman@gmail.com> 1242655012 +0000

Fix for PR2386: distinguish between insertion and replacements in the 
delta tree.

The issue is roughly a conflict in ReplaceText between two kinds of 
uses. One, it should be possible to replace a replacement: for example, the
ObjC rewriter calls ReplaceStmt for an expression, then replaces the resulting
expression with another expression.  Two, it should be possible to 
replace text that already has text inserted before it: for example, the 
HTML rewriter inserts a bunch of tags at the beginning of the line, then 
tries to escape the first character on the line.  This patch 
distinguishes the two cases by storing the deltas separately; 
essentially, replacements and insertions no longer interfere with 
each other.

Another possibility would be to add some sort of flag to ReplaceText, but
this seems a bit more intuitive and flexible.

There are a few downsides to the current solution: one is that there isn't
any way to remove/replace an insertion without touching additional
surrounding text; if such an operation turns out to be useful, an
additional method or flag can be added.  Another is that an insertion 
and replacing a string of length zero are distinct operations; I'm not 
sure how to resolve this, or whether it will be confusing in practice.

This is relatively sensitive code, so please test and tell me if 
anything breaks.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@72000 91177308-0d34-0410-b5e6-96231b3b80d8