- fixed the AnyRef linking (SI-5780)
- added tooltips to implicit conversions in diagrams
- fixed the intermittent dot error where node images would be left out
(dot is not reliable at all -- with all the mechanisms in place to fail
gracefully, we still get dot errors crawling their way into diagrams -
and that usually means no diagram generated, which is the most
appropriate way to fail, I think...)

…ion-pull-request

Ultimate reflection pull request #2

Turns importer caches into fully weak hash maps, and also applies
manual cleanup to toolboxes every time they are used.

It's not enough, because reflection-mem-typecheck test is still leaking
at a rate of ~100kb per typecheck, but it's much better than it was before.
We'll fix the rest later, after 2.10.0-final.

For more information, see https://issues.scala-lang.org/browse/SI-6412 and
http://groups.google.com/group/scala-internals/browse_thread/thread/eabcf3d406dab8b2

In comparison with scala@b403c1d,
the original commit that implemented the fix, this one doesn't crash tests.
The problem with the original commit was that it called tryFixup() before
updating the cache, leading to stack overflows.

SI-6412 alleviates leaks in toolboxes, attempt #2

blueprint CSS layout modified to 18-column from 24-column, spacing between paragraphs reduced by 1em

When an application of a blackbox macro still has undetermined type
parameters after Scala’s type inference algorithm has finished working,
these type parameters are inferred forcedly, in exactly the same manner
as type inference happens for normal methods.

This makes it impossible for blackbox macros to influence type inference,
prohibiting fundep materialization.

While fixing the problem with the order of typechecks for whitebox expansions,
I realized that we’re doing redundant work when expanding blackbox macros.
Concretely, typechecking blackbox expansions looked as follows:

  val expanded1 = atPos(enclosingMacroPosition.focus)(Typed(expanded0, TypeTree(innerPt)))
  val expanded2 = typecheck("blackbox typecheck #1", expanded1, innerPt)
  typecheck("blackbox typecheck #2", expanded1, outerPt)

Or, if we reformulate it using quasiquotes (temporarily not taking
positions into account, since they aren’t important here):

  val expanded2 = typed(q”$expanded: $innerPt”, innerPt)
  typed(expanded2, outerPt)

In this formulation, it becomes apparent that the first typecheck is
redundant. If something is ascribed with some type, then typechecking
the ascription against that type does nothing useful.

This is also highlights one of the reasons why it would be really nice
to have quasiquotes used in the compiler. With them, it’s easy to notice
things that would otherwise remain buried behind swaths of boilerplate.

[Parts of this patch and some of the commentary are from @paulp]

This took me so long to figure out I can't even tell you. Partly because
there were two different bugs, one which only arose for trait forwarders
and one for mirror class forwarders, and every time I'd make one set
of tests work another set would start failing. The runtime failures
associated with these bugs were fairly well hidden because you usually
have to go through java to encounter them: scala doesn't pay that much
attention to generic signatures, so they can be wrong and scala might still
generate correct code. But java is not so lucky.

Bug #1)

During mixin composition, classes which extend traits receive forwarders
to the implementations. An attempt was made to give these the correct
info (in method "cloneBeforeErasure") but it was prone to giving
the wrong answer, because: the key attribute which the forwarder
must capture is what the underlying method will erase to *where the
implementation is*, not how it appears to the class which contains it.
That means the signature of the forwarder must be no more precise than
the signature of the inherited implementation unless additional measures
will be taken.

This subtle difference will put on an unsubtle show for you in test
run/t3452.scala.

    trait C[T]
    trait Search[M] { def search(input: M): C[Int] = null }
    object StringSearch extends Search[String] { }
    StringSearch.search("test");  // java
    // java.lang.NoSuchMethodError: StringSearch.search(Ljava/lang/String;)LC;

The principled thing to do here would be to create a pair of
methods in the host class: a mixin forwarder with the erased
signature `(String)C[Int]`, and a bridge method with the same
erased signature as the trait interface facet.

But, this turns out to be pretty hard to retrofit onto the
current setup of Mixin and Erasure, mostly due to the fact
that mixin happens after erasure which has already taken
care of bridging.

For a future, release, we should try to move all bridging
after mixin, and pursue this approach. But for now, what can
we do about `LinkageError`s for Java clients?

This commit simply checks if the pre-erasure method signature
that we generate for the trait forward erases identically to
that of the interface method. If so, we can be precise. If not,
we emit the erased signature as the generic signature.

Bug #2) The same principle is at work, at a different location.
During genjvm, objects without declared companion classes
are given static forwarders in the corresponding class, e.g.

    object Foo { def bar = 5 }

which creates these classes (taking minor liberties):

    class Foo$ { static val MODULE$ = new Foo$ ; def bar = 5 }
    class Foo  { static def bar = Foo$.MODULE$.bar }

In generating these, genjvm circumvented the usual process whereby one
creates a symbol and gives it an info, preferring to target the bytecode
directly. However generic signatures are calculated from symbol info
(in this case reusing the info from the module class.) Lacking even the
attempt which was being made in mixin to "clone before erasure", we
would have runtime failures of this kind:

    abstract class Foo {
      type T
      def f(x: T): List[T] = List()
    }
    object Bar extends Foo { type T = String }
    Bar.f("");    // java
    // java.lang.NoSuchMethodError: Bar.f(Ljava/lang/String;)Lscala/collection/immutable/List;

Before/after this commit:

    <   signature                                     f  (Ljava/lang/String;)Lscala/collection/immutable/List<Ljava/lang/String;>;
    ---
    >   signature                                     f  (Ljava/lang/Object;)Lscala/collection/immutable/List<Ljava/lang/Object;>;

This takes the warning count for compiling collections under
`-Ycheck:jvm` from 1521 to 26.

Swathes of important logic are duplicated between `findMember`
and `findMembers` after they separated on grounds of irreconcilable
differences about how fast they should run:

    d905558 Variation scala#10 to optimze findMember
    fcb0c01 Attempt scala#9 to opimize findMember.
    71d2ceb Attempt scala#8 to opimize findMember.
    77e5692 Attempty scala#7 to optimize findMember
    275115e Fixing problem that caused fingerprints to fail in
    e94252e Attemmpt scala#6 to optimize findMember
    73e61b8 Attempt scala#5 to optimize findMember.
    04f0b65 Attempt scala#4 to optimize findMember
    0e3c70f Attempt scala#3 to optimize findMember
    41f4497 Attempt #2 to optimize findMember
    1a73aa0 Attempt #1 to optimize findMember

This didn't actually bear fruit, and the intervening years have
seen the implementations drift.

Now is the time to reunite them under the banner of `FindMemberBase`.

Each has a separate subclass to customise the behaviour. This is
primarily used by `findMember` to cache member types and to assemble
the resulting list of symbols in an low-allocation manner.

While there I have introduced some polymorphic calls, the call sites
are only bi-morphic, and our typical pattern of compilation involves
far more `findMember` calls, so I expect that JIT will keep the
virtual call cost to an absolute minimum.

Test results have been updated now that `findMembers` correctly
excludes constructors and doesn't inherit privates.

Coming up next: we can actually fix SI-7475!

As per discussion at https://groups.google.com/forum/#!topic/scala-internals/nf_ooEBn6-k,
this commit introduces the new c.enclosingOwner API that is going to serve
two purposes: 1) provide a better controlled alternative to c.enclosingTree,
2) enable low-level tinkering with owner chains without having to cast
to compiler internals.

This solution is not ideal, because: 1) symbols are much more than
I would like to expose about enclosing lexical contexts (after the
aforementioned discussion I’m no longer completely sure whether exposing
nothing is the right thing to do, but exposing symbol completers is definitely
something that should be avoided), 2) we shouldn’t have to do that
low-level stuff in the first place.

However, let’s face the facts. This change represents both an improvement
over the state of the art wrt #1 and a long-awaited capability wrt #2.
I think this pretty much warrants its place in trunk in the spirit of
gradual, evolutionary development of reflection API.

Under `-Ydelambdafy:method`, a public, static accessor method is
created to expose the private method containing the body of the
lambda.

Currently this accessor method has its parameters in the same order
structure as those of the lambda body method.

What is this order? There are three categories of parameters:

  1. lambda parameters
  2. captured parameters (added by lambdalift)
  3. self parameters (added to lambda bodies that end up in trait
     impl classes by mixin, and added unconditionally to the static
     accessor method.)

These are currently emitted in order scala#3, #1, #2.

Here are examples of the current behaviour:

BEFORE (trait):

```
% cat sandbox/test.scala && scalac-hash v2.11.5 -Ydelambdafy:method sandbox/test.scala && javap -private -classpath . 'Test$class'
trait Member; class Capture; trait LambdaParam
trait Test {
  def member: Member
  def foo {
    val local = new Capture
    (arg: LambdaParam) => "" + arg + member + local
  }
}
Compiled from "test.scala"
public abstract class Test$class {
  public static void foo(Test);
  private static final java.lang.String $anonfun$1(Test, LambdaParam, Capture);
  public static void $init$(Test);
  public static final java.lang.String accessor$1(Test, LambdaParam, Capture);
}
```

BEFORE (class):

```
% cat sandbox/test.scala && scalac-hash v2.11.5 -Ydelambdafy:method sandbox/test.scala && javap -private -classpath . Test
trait Member; class Capture; trait LambdaParam
abstract class Test {
  def member: Member
  def foo {
    val local = new Capture
    (arg: LambdaParam) => "" + arg + member + local
  }
}
Compiled from "test.scala"
public abstract class Test {
  public abstract Member member();
  public void foo();
  private final java.lang.String $anonfun$1(LambdaParam, Capture);
  public Test();
  public static final java.lang.String accessor$1(Test, LambdaParam, Capture);
}
```

Contrasting the class case with Java:

```
% cat sandbox/Test.java && javac -d . sandbox/Test.java && javap -private -classpath . Test
public abstract class Test {
  public static class Member {};
  public static class Capture {};
  public static class LambaParam {};
  public static interface I {
    public abstract Object c(LambaParam arg);
  }
  public abstract Member member();
  public void test() {
    Capture local = new Capture();
    I i1 = (LambaParam arg) -> "" + member() + local;
  }
}

Compiled from "Test.java"
public abstract class Test {
  public Test();
  public abstract Test$Member member();
  public void test();
  private java.lang.Object lambda$test$0(Test$Capture, Test$LambaParam);
}
```

We can see that in Java 8 lambda parameters come after captures. If we
want to use Java's LambdaMetafactory to spin up our anoymous FunctionN
subclasses on the fly, our ordering must change.

I can see three options for change:

  1. Adjust `LambdaLift` to always prepend captured parameters,
     rather than appending them. I think we could leave `Mixin` as
     it is, it already prepends the self parameter. This would result
     a parameter ordering, in terms of the list above: scala#3, #2, #1.
  2. More conservatively, do this just for methods known to hold
     lambda bodies. This might avoid needlessly breaking code that
     has come to depend on our binary encoding.
  3. Adjust the parameters of the accessor method only. The body
     of this method can permute params before calling the lambda
     body method.

This commit implements option #2.

In also prototyped #1, and found it worked so long as I limited it to
non-constructors, to sidestep the need to make corresponding
changes elsewhere in the compiler to avoid the crasher shown
in the enclosed test case, which was minimized from a bootstrap
failure from an earlier a version of this patch.

We would need to defer option #1 to 2.12 in any case, as some of
these lifted methods are publicied by the optimizer, and we must
leave the signatures alone to comply with MiMa.

I've included a test that shows this in all in action. However, that
is currently disabled, as we don't have a partest category for tests
that require Java 8.

The log messages intented to chronicle implicit search were
always being filtered out by virtue of the fact that the the tree
passed to `printTyping` was already typed, (e.g. with an implicit
MethodType.)

This commit enabled printing in this case, although it still
filters out trees that are deemed unfit for typer tracing,
such as `()`. In the context of implicit search, this happens
to filter out the noise of:

```
|    |    |    [search #2] start `()`, searching for adaptation to pt=Unit => Foo[Int,Int] (silent: value <local Test> in Test) implicits disabled
|    |    |    [search scala#3] start `()`, searching for adaptation to pt=(=> Unit) => Foo[Int,Int] (silent: value <local Test> in Test) implicits disabled
|    |    |    \-> <error>
```

... which I think is desirable.

The motivation for this fix was to better display the interaction
between implicit search and type inference. For instance:

```
class Foo[A, B]
class Test {
  implicit val f: Foo[Int, String] = ???
  def t[A, B](a: A)(implicit f: Foo[A, B]) = ???
  t(1)
}
```

````
% scalac -Ytyper-debug sandbox/instantiate.scala
...
|    |-- t(1) BYVALmode-EXPRmode (site: value <local Test> in Test)
|    |    |-- t BYVALmode-EXPRmode-FUNmode-POLYmode (silent: value <local Test> in Test)
|    |    |    [adapt] [A, B](a: A)(implicit f: Foo[A,B])Nothing adapted to [A, B](a: A)(implicit f: Foo[A,B])Nothing
|    |    |    \-> (a: A)(implicit f: Foo[A,B])Nothing
|    |    |-- 1 BYVALmode-EXPRmode-POLYmode (site: value <local Test> in Test)
|    |    |    \-> Int(1)
|    |    solving for (A: ?A, B: ?B)
|    |    solving for (B: ?B)
|    |    [search #1] start `[A, B](a: A)(implicit f: Foo[A,B])Nothing` inferring type B, searching for adaptation to pt=Foo[Int,B] (silent: value <local Test> in Test) implicits disabled
|    |    [search #1] considering f
|    |    [adapt] f adapted to => Foo[Int,String] based on pt Foo[Int,B]
|    |    [search #1] solve tvars=?B, tvars.constr= >: String <: String
|    |    solving for (B: ?B)
|    |    [search #1] success inferred value of type Foo[Int,=?String] is SearchResult(Test.this.f, TreeTypeSubstituter(List(type B),List(String)))
|    |    |-- [A, B](a: A)(implicit f: Foo[A,B])Nothing BYVALmode-EXPRmode (site: value <local Test> in Test)
|    |    |    \-> Nothing
|    |    [adapt] [A, B](a: A)(implicit f: Foo[A,B])Nothing adapted to [A, B](a: A)(implicit f: Foo[A,B])Nothing
|    |    \-> Nothing
```