refactors macro compilation

Upgrades the way that macro defs are compiled by factoring out most of
the logic in typedMacroBody and related errors in ContextErrors into an
standalone cake. This leads to tighter cohesion and better code reuse
as the cake is isolated from the rest of the compiler and is much easier
to evolve than just a method body.

Increased convenience of coding macro compilation allowed me to further
clarify the implementation of the macro engine (e.g. take a look at
Validators.scala) and to easily implement additional features, namely:

1) Parameters and return type of macro implementations can now be plain
c.Tree's instead of previously mandatory c.Expr's. This makes macros more
lightweight as there are a lot of situations when one doesn't need to
splice macro params (the only motivation to use exprs over trees). Also
as we're on the verge of having quasiquotes in trunk, there soon will be
no reason to use exprs at all, since quasiquotes can splice everything.

2) Macro implementations can now be defined in bundles, standalone cakes
built around a macro context: http://docs.scala-lang.org/overviews/macros/bundles.html.
This further reduces boilerplate by simplifying implementations complex
macros due to the fact that macro programmers no longer need to play
path-dependent games to use helpers.

1 files changed, 6 insertions, 8 deletions

diff --git a/test/files/neg/macro-invalidshape.check b/test/files/neg/macro-invalidshape.check
index cefc95b763..40a2952569 100644
--- a/test/files/neg/macro-invalidshape.check
+++ b/test/files/neg/macro-invalidshape.check
@@ -1,17 +1,15 @@
-Macros_Test_2.scala:2: error: macro body has wrong shape:
- required: macro [<implementation object>].<method name>[[<type args>]]
+Macros_Test_2.scala:2: error: macro implementation reference has wrong shape. required:
+macro [<static object>].<method name>[[<type args>]] or
+macro [<macro bundle>].<method name>[[<type args>]]
   def foo1(x: Any) = macro 2
       ^
-Macros_Test_2.scala:3: error: macro body has wrong shape:
- required: macro [<implementation object>].<method name>[[<type args>]]
+Macros_Test_2.scala:3: error: macro implementation reference has wrong shape. required:
+macro [<static object>].<method name>[[<type args>]] or
+macro [<macro bundle>].<method name>[[<type args>]]
   def foo2(x: Any) = macro Impls.foo(null)(null)
       ^
-Macros_Test_2.scala:4: warning: a pure expression does nothing in statement position; you may be omitting necessary parentheses
-  def foo3(x: Any) = macro {2; Impls.foo}
-                            ^
 Macros_Test_2.scala:4: error: missing arguments for method foo in object Impls;
 follow this method with `_' if you want to treat it as a partially applied function
   def foo3(x: Any) = macro {2; Impls.foo}
                                      ^
-one warning found
 three errors found