introduces Unquote #112

xeno-by · 2015-03-01T16:24:35Z

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@ast

I'm about to significantly change @ast codegen, so we need these additional tests to make sure that nothing breaks down the road.

@root

I'm about to introduce impl.Unquote, which has to be a subtype of all tree nodes. However unpleasant the consequences are, we have to deal with them, because we currently don't know of an alternative technology to implement quasiquotes in a principled manner. What we discussed with Denys is that we might be able to get back the guarantees offered by sealedness if we find a way to customize exhaustivity checks in the pattern matcher from a compiler plugin. People are going to use scalahost anyway, so it could also do additional domain-specific exhaustivity checking. This commit also comes with some refactoring of the adt/ast infrastructure. In particular, all checks now return q"()" instead of q"", which has uncovered a terrible bug. If a trait def has the INTERFACE flag set, then essentially any statement in its body (e.g. q"()") is going to crash the compiler. Therefore, I'm manually resetting the INTERFACE flag in @root and @Branch. This, in turn, led to problems with `@branch trait Defn`, because it makes scalac emit `Defn$class`, which comes in conflict with `Defn$Class`. To address that, I had to temporarily disable all checks for Defn.

As explained in the parent's commit message, we had to reset INTERFACE, because our codegen emits statements into templates of the annottees, and GenICode really doesn't like it when a template of an INTERFACE trait has statements in it. Now it's time for a principled solution. All statements are now moved to companions of the annottees, and everyone's happy.

@ast

I'm about to introduce scala.meta.internal.ast.Unquote, which has to be a subtype of all tree nodes. For that, we need to make it possible to subclass @ast classes. The solution that I'll be pursuing in this and subsequent commits is splitting `@ast class Foo` into `trait Foo; object Foo { class Impl extends Foo }`. This is a very heavy-handed way of organizing the @ast codegen, but it looks like we don't have much choice. A pleasant side-effect of this change is the ability to proxy trees, so that, for example, we can lazily load bodies of vals/vars/defs. Nothing in that direction is implemented just yet. We will cross that bridge when we get there - now is not the time.

@ast

In order to be able to subclass all @ast traits, Unquote needs those traits to be devoid of any methods. Therefore, since this commit, we split all @ast classes into three entities: an empty trait, an API-carrying trait and an implementation class.

Unfortunately, having an Interface => Api implicit conversion is not enough, because we have things like Member.name in the semantic API, and those come in conflict. Therefore, we'll have to move ast fields to the interface part, and then have Unquote implement ALL those fields with ??? or something similar.

@ast

This is a funny class that is a subclass of all ast classes in scala.meta. At the moment it's just `@bottom @ast class Unquote() extends Tree`, but later on we'll decide how it fields should look like.

Now when we accumulate all ast classes in parents of Unquote, we don't need an additional mechanism to track those classes.

It turns out that it can be perfectly represented by meta.Name.Indeterminate.

This takes care of the last place in the tree API, where we represented names with strings, and makes our tree API maximally friendly to Unquote. It's a bit of stretch to use Name.Qualifier here, because along with anonymous and indeterminate names (which fit), Name.Qualifier also covers Term.This (which doesn't fit), but I didn't feel like introducing a new public trait just to have this extra bit of static safety. Maybe in the future we'll have to change this decision. Having this change in place also means that This and Super don't have to be names anymore. This, in turn, means that Name.Qualifier can no longer be a Name and becomes a Ref. This also means that Member.name can no longer be a Name, but that was too much for me, so now it's still a Name, but it does not return This anymore. All in all, this worked pretty well. I'm not sure whether I like the fact that `this` and `super` are no longer names, but I can try to get accustomed to that.

introduces Unquote

xeno-by added 17 commits February 28, 2015 15:00

additional testing for the AdtReflection infrastructure

e1098a6

I'm about to significantly change @ast codegen, so we need these additional tests to make sure that nothing breaks down the road.

fixes the problem with allBranches and allLeafs producing duplicates

9f43d9c

highlights adt/ast codegen changes

4d20b9e

trivializes @ast traits

a899a2d

In order to be able to subclass all @ast traits, Unquote needs those traits to be devoid of any methods. Therefore, since this commit, we split all @ast classes into three entities: an empty trait, an API-carrying trait and an implementation class.

we also can't have type ThisType = ... in @ast traits anymore

85a5357

updates ast.md

ac955ae

introduces Unquote

89730ed

This is a funny class that is a subclass of all ast classes in scala.meta. At the moment it's just `@bottom @ast class Unquote() extends Tree`, but later on we'll decide how it fields should look like.

removes Registry

a703a8d

Now when we accumulate all ast classes in parents of Unquote, we don't need an additional mechanism to track those classes.

accounts for all ast field types

c5078da

removes meta.Name.Imported

b6beae7

It turns out that it can be perfectly represented by meta.Name.Indeterminate.

Name.AccessBoundary => Name.Qualifier

957c1a0

updates the docs

d0c416b

xeno-by added a commit that referenced this pull request Mar 1, 2015

Merge pull request #112 from xeno-by/master

49258a7

introduces Unquote

xeno-by merged commit 49258a7 into scalameta:master Mar 1, 2015

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introduces Unquote #112

introduces Unquote #112

xeno-by commented Mar 1, 2015

introduces Unquote #112

introduces Unquote #112

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xeno-by commented Mar 1, 2015