1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
|
package magnolia
import scala.reflect._, macros._
import macrocompat.bundle
import scala.util.Try
import language.existentials
import scala.collection.immutable.ListMap
case class Pos(pos: api.Position) {
override def toString = s"${pos.line}:${pos.column}"
}
case class ReentrantException() extends Exception("attempt to recurse directly")
object GlobalMutableState {
private[magnolia] var state: Map[Pos, ListMap[c.universe.Type forSome { val c: whitebox.Context }, c.universe.TermName forSome { val c: whitebox.Context }]] = Map()
private[magnolia] def push(c: whitebox.Context)(key: c.universe.Type, value: c.universe.TermName): Unit = {
println(s"push($key)")
state = state.updated(Pos(c.enclosingPosition), state.get(Pos(c.enclosingPosition)).map { m =>
m.updated(key, value)
}.getOrElse(ListMap(key -> value)))
println("state = "+state)
}
private[magnolia] def pop(c: whitebox.Context): Unit = {
println(s"pop(${state(Pos(c.enclosingPosition)).last})")
state = state.updated(Pos(c.enclosingPosition), state(Pos(c.enclosingPosition)).init)
println("state = "+state)
}
private[magnolia] def has(c: whitebox.Context)(key: c.universe.Type): Option[c.universe.TermName] =
try state(Pos(c.enclosingPosition)).get(key).asInstanceOf[Option[c.universe.TermName]] catch {
case e: Exception =>
???
}
private[magnolia] var searchType: AnyRef = null
}
@bundle
class Macros(val context: whitebox.Context) extends GenericMacro(context) {
protected def classBody(context: whitebox.Context)(genericType: context.Type, implementation: context.Tree): context.Tree = {
import context.universe._
q"""def extract(src: _root_.magnolia.Thing): $genericType = $implementation"""
}
protected def dereferenceValue(context: whitebox.Context)(value: context.Tree, elem: String): context.Tree = {
import context.universe._
q"$value.access($elem)"
}
protected def callDelegateMethod(context: whitebox.Context)(value: context.Tree, argument: context.Tree): context.Tree = {
import context.universe._
q"$value.extract($argument)"
}
protected def coproductReduction(context: whitebox.Context)(left: context.Tree, right: context.Tree): context.Tree = {
import context.universe._
q"$left.orElse($right)"
}
}
abstract class GenericMacro(whiteboxContext: whitebox.Context) {
val c = whiteboxContext
def getImplicit(genericType: c.universe.Type,
typeConstructor: c.universe.Type,
myName: c.universe.TermName,
count: Int): c.Tree = {
import c.universe._
println(s"getImplicit1($genericType, $count)")
val x = GlobalMutableState.has(c)(genericType)
x.foreach { y => println("y = "+y) }
val result = x.map { nm =>
q"$nm"
}.orElse {
val searchType = appliedType(typeConstructor, genericType)
if(GlobalMutableState.has(c)(genericType).isEmpty) {
GlobalMutableState.searchType = genericType
val inferredImplicit = try Some(c.inferImplicitValue(searchType, false, false)) catch {
case e: Exception => None
}
object transformer extends Transformer {
override def transform(tree: Tree): Tree = tree match {
case ta@TypeApply(Select(Literal(Constant(method: String)), TermName("asInstanceOf")), List(tpe)) =>
println(s"Found typeapply: ${tpe}")
val m = TermName(method)
q"$m"
case _ => super.transform(tree)
}
}
inferredImplicit.map { imp =>
transformer.transform(imp)
}.orElse {
directInferImplicit(genericType, typeConstructor, count + 1)
}
} else {
directInferImplicit(genericType, typeConstructor, count + 1)
}
}.getOrElse {
println("Really failed to find extractor for type "+genericType)
c.abort(c.enclosingPosition, "Could not find extractor for type "+genericType)
}
//println(" = "+result)
result
}
def directInferImplicit(genericType: c.universe.Type,
typeConstructor: c.universe.Type,
count: Int): Option[c.Tree] = {
import c.universe._
println(s"directInferImplicit($genericType, $count)")
val myName: TermName = TermName(c.freshName(genericType.typeSymbol.name.encodedName.toString.toLowerCase+"Extractor"))
val typeSymbol = genericType.typeSymbol
val classType = if(typeSymbol.isClass) Some(typeSymbol.asClass) else None
val isCaseClass = classType.map(_.isCaseClass).getOrElse(false)
val isSealedTrait = classType.map(_.isSealed).getOrElse(false)
val isAnyVal = genericType <:< typeOf[AnyVal]
val resultType = appliedType(typeConstructor, genericType)
val construct = if(isCaseClass) {
val implicits = genericType.decls.collect {
case m: MethodSymbol if m.isCaseAccessor => m.asMethod
}.map { param =>
val returnType = param.returnType
GlobalMutableState.push(c)(genericType, myName)
val imp = getImplicit(returnType, typeConstructor, myName, count)
GlobalMutableState.pop(c)
val dereferenced = dereferenceValue(c)(q"src", param.name.toString)
callDelegateMethod(c)(imp, dereferenced)
}
Some(q"new $genericType(..$implicits)")
} else if(isSealedTrait) {
val subtypes = classType.get.knownDirectSubclasses.to[List]
Some(subtypes.map(_.asType.toType).map { searchType =>
GlobalMutableState.push(c)(genericType, myName)
val res = getImplicit(searchType, typeConstructor, myName, count)
GlobalMutableState.pop(c)
res
}.reduce(coproductReduction(c))).map { imp =>
callDelegateMethod(c)(imp, q"src")
}
} else None
val result = construct.map { const =>
val methodImplementation = classBody(c)(genericType, const)
q"""{
def $myName: $resultType = new $resultType {
$methodImplementation
}
$myName
}"""
}
result
}
protected def classBody(c: whitebox.Context)(genericType: c.Type, implementation: c.Tree): c.Tree
protected def coproductReduction(c: whitebox.Context)(left: c.Tree, right: c.Tree): c.Tree
protected def dereferenceValue(c: whitebox.Context)(value: c.Tree, elem: String): c.Tree
protected def callDelegateMethod(c: whitebox.Context)(value: c.Tree, argument: c.Tree): c.Tree
def generic[T: c.WeakTypeTag, Tc: c.WeakTypeTag]: c.Tree = try {
import c.universe._
println("Entering generic for type "+weakTypeOf[T])
val genericType: Type = weakTypeOf[T]
val reentrant = genericType == GlobalMutableState.searchType
println(s"LAST TYPE = ${GlobalMutableState.searchType}; THIS TYPE = $genericType")
val result: Option[c.Tree] = if(reentrant) {
println("Reentrant.")
throw ReentrantException()
} else if(GlobalMutableState.searchType != null) {
GlobalMutableState.has(c)(genericType) match {
case None =>
val typeConstructor: Type = weakTypeOf[Tc].typeConstructor
directInferImplicit(genericType, typeConstructor, 0)
case Some(t) =>
val str = t.toString
val typeConstructor: Type = weakTypeOf[Tc].typeConstructor
val searchType = appliedType(typeConstructor, genericType)
Some(q"$str.asInstanceOf[${searchType}]")
}
} else {
val typeConstructor: Type = weakTypeOf[Tc].typeConstructor
directInferImplicit(genericType, typeConstructor, 0)
}
println(result)
try result.map { tree => c.typecheck(tree) } catch {
case e: Exception =>
println(result)
println("Failed to typecheck because: "+e)
}
result.getOrElse {
println("FAIL.")
c.abort(c.enclosingPosition, "Could not infer extractor. Sorry.")
}
} catch {
case e@ReentrantException() => throw e
case e: Exception =>
println("Oh no, there was a problem: "+e)
e.printStackTrace()
???
}
}
|
