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Performs the following renamings:
* scala.reflect.macros.BlackboxContext to scala.reflect.macros.blackbox.Context
* scala.reflect.macros.BlackboxMacro to scala.reflect.macros.blackbox.Macro
* scala.reflect.macros.WhiteboxContext to scala.reflect.macros.whitebox.Context
* scala.reflect.macros.WhiteboxMacro to scala.reflect.macros.whitebox.Macro
https://groups.google.com/forum/#!topic/scala-internals/MX40-dM28rk
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With the new focus on quasiquotes in macro implementations, we now have
to change the way how inference of macro def return types works.
Previously, if the return type of a macro def wasn’t specified, we looked into
the signature of its macro impl, took its return type (which could only
be c.Expr[T]) and then assigned T to be the return type of the macro def.
We also had a convenient special case which inferred Any in case when
the body of the macro impl wasn’t an expr. That avoided reporting spurious
errors if the macro impl had its body typed incorrectly (because in that
case we would report a def/impl signature mismatch anyway) and also provided
a convenience by letting macro impls end with `???`.
However now we also allow macro impls to return c.Tree, which means that
we are no longer able to do any meaningful type inference, because c.Tree
could correspond to tree of any type.
Unfortunately, when coupled with the type inference special case described
above, this means that the users who migrate from exprs to quasiquotes
are going to face an unpleasant surprise. If they haven’t provided
explicit return types for their macro defs, those types are going to be
silently inferred as `Any`!
This commit plugs this loophole by prohibiting type inference from
non-expr return types of macro impls (not counting Nothing). Moreover,
it also deprecates c.Expr[T] => T inference in order to avoid confusion
when switching between exprs and quasiquotes.
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This is the first commit in the series. This commit only:
1) Splits Context into BlackboxContext and WhiteboxContext
2) Splits Macro into BlackboxMacro and WhiteboxMacro
3) Introduces the isBundle property in the macro impl binding
Here we just teach the compiler that macros can now be blackbox and whitebox,
without actually imposing any restrictions on blackbox macros. These
restrictions will come in subsequent commits.
For description and documentation of the blackbox/whitebox separation
see the official macro guide at the scaladoc website:
http://docs.scala-lang.org/overviews/macros/blackbox-whitebox.html
Some infrastructure work to make evolving macros easier:
compile partest-extras with quick so they can use latest library/reflect/...
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With the advent of quasiquotes, we allowed both arguments and return types
of macro impls to be c.Tree's (as opposed to traditional c.Expr[T]'s).
This warrants an update of macro def <-> macro impl signature mismatch
errors that include a printout of suggested macro impl signatures. Now
along with a signature that contains exprs, we suggest another signature
that has all exprs replaced by trees
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Previously it was enough to just extend scala.reflect.macros.Macro, which
created some loopholes, but now scalac enforces that bundles:
1) Are static (not necessarily top-level, but just static)
2) Are traits (objects shouldn't be bundles anyway, and classes bring
complications with their ctors which require special treatment in
generated classes, so why support them if they don't bring anything
new to the table?)
3) Are monomorphic (again, this brings unnecessary complications wrt
auxiliary code generation, so I don't see merit in supporting
polymorphic bundles, whatever that a polymorphic bundle could mean)
4) Don't provide concrete implementation for Macro.c (if they do then
what is the point?)
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