go/scanner: clean up error interface

Issue 2856 asks for a rename of a few methods to a
more idiomatic Go style. This is a very early API
that evolved organically throughout the years.
Together with the fact that ErrorVectors were embedded
in other data structures (e.g. Parser), just renaming
methods (e.g. GetError -> Error) would lead to undesired
behavior (e.g., Parser would act like an Error). Instead,
cleaned up API a bit more:

- removed ErrorVector in favor of ErrorList (already
present)
- simplified Scanner.Init by making the error handler a
function instead of requiring an ErrorHandler implementation
- adjusted helper functions accordingly
- updated Go 1 doc

Fixes issue 2856.

R=rsc
CC=golang-dev
http://codereview.appspot.com/5624047

1 files changed, 10 insertions, 0 deletions

diff --git a/doc/go1.html b/doc/go1.html
index e3d2354e6..7613c3880 100644
--- a/doc/go1.html
+++ b/doc/go1.html
@@ -1042,6 +1042,16 @@ for that purpose.
 </p>
 
 <p>
+The <a href="/pkg/go/scanner/#ErrorHandler"><code>ErrorHandler</code></a> provided
+to the scanner's <a href="/pkg/go/scanner/#Scanner.Init"><code>Init</code></a> method is
+now simply a function rather than an interface. The <code>ErrorVector</code> type has
+been removed in favor of the (existing) <a href="/pkg/go/scanner/#ErrorList"><code>ErrorList</code></a>
+type, and the <code>ErrorVector</code> methods have been migrated. Instead of embedding
+an <code>ErrorVector</code> in a client of the scanner, now a client should maintain
+an <code>ErrorList</code>.
+</p>
+
+<p>
 The set of parse functions provided by the <a href="/pkg/go/parser/"><code>go/parser</code></a>
 package has been reduced to the primary parse function
 <a href="/pkg/go/parser/#ParseFile"><code>ParseFile</code></a>, and a couple of