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
|
/* NSC -- new Scala compiler
* Copyright 2005-2013 LAMP/EPFL
* Author: Paul Phillips
*/
package scala.tools.nsc
package matching
import transform.ExplicitOuter
import PartialFunction._
/** Traits which are mixed into MatchMatrix, but separated out as
* (somewhat) independent components to keep them on the sidelines.
*/
trait MatrixAdditions extends ast.TreeDSL {
self: ExplicitOuter with ParallelMatching =>
import global.{ typer => _, _ }
import symtab.Flags
import CODE._
import Debug._
import treeInfo._
import definitions.{ isPrimitiveValueClass }
/** The Squeezer, responsible for all the squeezing.
*/
private[matching] trait Squeezer {
self: MatrixContext =>
private val settings_squeeze = !settings.Ynosqueeze.value
class RefTraverser(vd: ValDef) extends Traverser {
private val targetSymbol = vd.symbol
private var safeRefs = 0
private var isSafe = true
def canDrop = isSafe && safeRefs == 0
def canInline = isSafe && safeRefs == 1
override def traverse(tree: Tree): Unit = tree match {
case t: Ident if t.symbol eq targetSymbol =>
// target symbol's owner should match currentOwner
if (targetSymbol.owner == currentOwner) safeRefs += 1
else isSafe = false
case LabelDef(_, params, rhs) =>
if (params exists (_.symbol eq targetSymbol)) // cannot substitute this one
isSafe = false
traverse(rhs)
case _ if safeRefs > 1 => ()
case _ =>
super.traverse(tree)
}
}
/** Compresses multiple Blocks. */
private def combineBlocks(stats: List[Tree], expr: Tree): Tree = expr match {
case Block(stats1, expr1) if stats.isEmpty => combineBlocks(stats1, expr1)
case _ => Block(stats, expr)
}
def squeezedBlock(vds: List[Tree], exp: Tree): Tree =
if (settings_squeeze) combineBlocks(Nil, squeezedBlock1(vds, exp))
else combineBlocks(vds, exp)
private def squeezedBlock1(vds: List[Tree], exp: Tree): Tree = {
lazy val squeezedTail = squeezedBlock(vds.tail, exp)
def default = squeezedTail match {
case Block(vds2, exp2) => Block(vds.head :: vds2, exp2)
case exp2 => Block(vds.head :: Nil, exp2)
}
if (vds.isEmpty) exp
else vds.head match {
case vd: ValDef =>
val rt = new RefTraverser(vd)
rt.atOwner(owner)(rt traverse squeezedTail)
if (rt.canDrop)
squeezedTail
else if (isConstantType(vd.symbol.tpe) || rt.canInline)
new TreeSubstituter(List(vd.symbol), List(vd.rhs)) transform squeezedTail
else
default
case _ => default
}
}
}
/** The Optimizer, responsible for some of the optimizing.
*/
private[matching] trait MatchMatrixOptimizer {
self: MatchMatrix =>
import self.context._
final def optimize(tree: Tree): Tree = {
// Uses treeInfo extractors rather than looking at trees directly
// because the many Blocks obscure our vision.
object lxtt extends Transformer {
override def transform(tree: Tree): Tree = tree match {
case Block(stats, ld @ LabelDef(_, _, body)) if targets exists (_ shouldInline ld.symbol) =>
squeezedBlock(transformStats(stats, currentOwner), body)
case IsIf(cond, IsTrue(), IsFalse()) =>
transform(cond)
case IsIf(cond1, IsIf(cond2, thenp, elsep1), elsep2) if elsep1 equalsStructure elsep2 =>
transform(typer typed If(gen.mkAnd(cond1, cond2), thenp, elsep2))
case If(cond1, IsIf(cond2, thenp, Apply(jmp, Nil)), ld: LabelDef) if jmp.symbol eq ld.symbol =>
transform(typer typed If(gen.mkAnd(cond1, cond2), thenp, ld))
case _ =>
super.transform(tree)
}
}
try lxtt transform tree
finally clearSyntheticSyms()
}
}
/** The Exhauster.
*/
private[matching] trait MatrixExhaustiveness {
self: MatchMatrix =>
import self.context._
/** Exhaustiveness checking requires looking for sealed classes
* and if found, making sure all children are covered by a pattern.
*/
class ExhaustivenessChecker(rep: Rep, matchPos: Position) {
val Rep(tvars, rows) = rep
import Flags.{ MUTABLE, ABSTRACT, SEALED }
private case class Combo(index: Int, sym: Symbol) { }
/* True if the patterns in 'row' cover the given type symbol combination, and has no guard. */
private def rowCoversCombo(row: Row, combos: List[Combo]) =
row.guard.isEmpty && combos.forall(c => row.pats(c.index) covers c.sym)
private def requiresExhaustive(sym: Symbol) = {
(sym.isMutable) && // indicates that have not yet checked exhaustivity
!(sym hasFlag NO_EXHAUSTIVE) && // indicates @unchecked
(sym.tpe.typeSymbol.isSealed) &&
!isPrimitiveValueClass(sym.tpe.typeSymbol) // make sure it's not a primitive, else (5: Byte) match { case 5 => ... } sees no Byte
}
private lazy val inexhaustives: List[List[Combo]] = {
// let's please not get too clever side-effecting the mutable flag.
val toCollect = tvars.zipWithIndex filter { case (pv, i) => requiresExhaustive(pv.sym) }
val collected = toCollect map { case (pv, i) =>
// okay, now reset the flag
pv.sym resetFlag MUTABLE
i -> (
pv.tpe.typeSymbol.sealedDescendants.toList sortBy (_.sealedSortName)
// symbols which are both sealed and abstract need not be covered themselves, because
// all of their children must be and they cannot otherwise be created.
filterNot (x => x.isSealed && x.isAbstractClass && !isPrimitiveValueClass(x))
// have to filter out children which cannot match: see ticket #3683 for an example
filter (_.tpe matchesPattern pv.tpe)
)
}
val folded =
collected.foldRight(List[List[Combo]]())((c, xs) => {
val (i, syms) = c match { case (i, set) => (i, set.toList) }
xs match {
case Nil => syms map (s => List(Combo(i, s)))
case _ => for (s <- syms ; rest <- xs) yield Combo(i, s) :: rest
}
})
folded filterNot (combo => rows exists (r => rowCoversCombo(r, combo)))
}
private def mkPad(xs: List[Combo], i: Int): String = xs match {
case Nil => pad("*")
case Combo(j, sym) :: rest => if (j == i) pad(sym.name.toString) else mkPad(rest, i)
}
private def mkMissingStr(open: List[Combo]) =
"missing combination %s\n" format tvars.indices.map(mkPad(open, _)).mkString
/** The only public method. */
def check = {
def errMsg = (inexhaustives map mkMissingStr).mkString
if (inexhaustives.nonEmpty)
cunit.warning(matchPos, "match is not exhaustive!\n" + errMsg)
rep
}
}
}
}
|
