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nicolasstuckinicolasstucki
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Dealias quoted types when staging (#17059)
This change improves the code generation of the contents of splices. In the splicing phase, we have to find all types that are defined in the quote but used in the splice. When there are type aliases, we can end up with several `Type[T]` for the different aliases of `T`. By dealiasing during the staging phase (just before splicing phase) we make sure that the splicer phase will only generate one `Type[T]`. By dealiasing we also optimize some situations where a type from outside a quote is inserted in the quoted code and then used in one of its splice through an alias. In this situation we can use the outer `Type[T]` directly. ### Example After staging the following code should get what is in the comments ```scala import scala.quoted.* def f[T](using t: Type[T])(using Quotes) = '{ // @SplicedType type t$1 = t.Underlying type T2 = T // type T2 = t$1 ${ val t0: T = ??? val t1: T2 = ??? // val t1: T = ??? val tp1 = Type.of[T] // val tp1 = t val tp2 = Type.of[T2] // val tp2 = t '{ // @SplicedType type t$2 = t.Underlying val t3: T = ??? // val t3: t$2 = ??? val t4: T2 = ??? // val t4: t$2 = ??? } } } def g(using Quotes) = '{ type U type U2 = U ${ val u1: U = ??? val u2: U2 = ??? // val u2: U = ??? val tp1 = Type.of[U] // val tp1 = Type.of[U] val tp2 = Type.of[U2] // val tp2 = Type.of[U] '{ val u3: U = ??? val u4: U2 = ??? // val u4: U = ??? } } } ```
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‎compiler/src/dotty/tools/dotc/staging/CrossStageSafety.scala

Lines changed: 21 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -107,30 +107,37 @@ class CrossStageSafety extends TreeMapWithStages {
107107
val stripAnnotsDeep: TypeMap = new TypeMap:
108108
def apply(tp: Type): Type = mapOver(tp.stripAnnots)
109109

110-
val contextWithQuote =
111-
if level == 0 then contextWithQuoteTypeTags(taggedTypes)(using quoteContext)
112-
else quoteContext
113-
val body1 = transform(body)(using contextWithQuote)
114-
val body2 =
110+
def transformBody() =
111+
val contextWithQuote =
112+
if level == 0 then contextWithQuoteTypeTags(taggedTypes)(using quoteContext)
113+
else quoteContext
114+
val transformedBody = transform(body)(using contextWithQuote)
115115
taggedTypes.getTypeTags match
116-
case Nil => body1
117-
case tags => tpd.Block(tags, body1).withSpan(body.span)
116+
case Nil => transformedBody
117+
case tags => tpd.Block(tags, transformedBody).withSpan(body.span)
118118

119119
if body.isTerm then
120+
val transformedBody = transformBody()
120121
// `quoted.runtime.Expr.quote[T](<body>)` --> `quoted.runtime.Expr.quote[T2](<body2>)`
121122
val TypeApply(fun, targs) = quote.fun: @unchecked
122123
val targs2 = targs.map(targ => TypeTree(healType(quote.fun.srcPos)(stripAnnotsDeep(targ.tpe))))
123-
cpy.Apply(quote)(cpy.TypeApply(quote.fun)(fun, targs2), body2 :: Nil)
124+
cpy.Apply(quote)(cpy.TypeApply(quote.fun)(fun, targs2), transformedBody :: Nil)
124125
else
125-
val quotes = quote.args.mapConserve(transform)
126126
body.tpe match
127-
case tp @ TypeRef(x: TermRef, _) if tp.symbol == defn.QuotedType_splice =>
127+
case DirectTypeOf(termRef) =>
128128
// Optimization: `quoted.Type.of[x.Underlying](quotes)` --> `x`
129-
ref(x)
129+
ref(termRef).withSpan(quote.span)
130130
case _ =>
131-
// `quoted.Type.of[<body>](quotes)` --> `quoted.Type.of[<body2>](quotes)`
132-
val TypeApply(fun, _) = quote.fun: @unchecked
133-
cpy.Apply(quote)(cpy.TypeApply(quote.fun)(fun, body2 :: Nil), quotes)
131+
transformBody() match
132+
case DirectTypeOf.Healed(termRef) =>
133+
// Optimization: `quoted.Type.of[@SplicedType type T = x.Underlying; T](quotes)` --> `x`
134+
ref(termRef).withSpan(quote.span)
135+
case transformedBody =>
136+
val quotes = quote.args.mapConserve(transform)
137+
// `quoted.Type.of[<body>](quotes)` --> `quoted.Type.of[<body2>](quotes)`
138+
val TypeApply(fun, _) = quote.fun: @unchecked
139+
cpy.Apply(quote)(cpy.TypeApply(quote.fun)(fun, transformedBody :: Nil), quotes)
140+
134141
}
135142

136143
/** Transform splice

‎compiler/src/dotty/tools/dotc/staging/DirectTypeOf.scala

Lines changed: 25 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,25 @@
1+
package dotty.tools.dotc.staging
2+
3+
import dotty.tools.dotc.ast.{tpd, untpd}
4+
import dotty.tools.dotc.core.Contexts._
5+
import dotty.tools.dotc.core.Symbols._
6+
import dotty.tools.dotc.core.Types._
7+
8+
object DirectTypeOf:
9+
import tpd.*
10+
11+
/** Matches `x.Underlying` and extracts the TermRef to `x` */
12+
def unapply(tpe: Type)(using Context): Option[TermRef] = tpe match
13+
case tp @ TypeRef(x: TermRef, _) if tp.symbol == defn.QuotedType_splice => Some(x)
14+
case _ => None
15+
16+
object Healed:
17+
/** Matches `{ @SplicedType type T = x.Underlying; T }` and extracts the TermRef to `x` */
18+
def unapply(body: Tree)(using Context): Option[TermRef] =
19+
body match
20+
case Block(List(tdef: TypeDef), tpt: TypeTree) =>
21+
tpt.tpe match
22+
case tpe: TypeRef if tpe.typeSymbol == tdef.symbol =>
23+
DirectTypeOf.unapply(tdef.rhs.tpe.hiBound)
24+
case _ => None
25+
case _ => None

‎compiler/src/dotty/tools/dotc/staging/HealType.scala

Lines changed: 9 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -32,7 +32,12 @@ class HealType(pos: SrcPos)(using Context) extends TypeMap {
3232
def apply(tp: Type): Type =
3333
tp match
3434
case tp: TypeRef =>
35-
healTypeRef(tp)
35+
tp.underlying match
36+
case TypeAlias(alias)
37+
if !tp.symbol.isTypeSplice && !tp.typeSymbol.hasAnnotation(defn.QuotedRuntime_SplicedTypeAnnot) =>
38+
this.apply(alias)
39+
case _ =>
40+
healTypeRef(tp)
3641
case tp @ TermRef(NoPrefix, _) if !tp.symbol.isStatic && level > levelOf(tp.symbol) =>
3742
levelError(tp.symbol, tp, pos)
3843
case tp: AnnotatedType =>
@@ -46,11 +51,11 @@ class HealType(pos: SrcPos)(using Context) extends TypeMap {
4651
checkNotWildcardSplice(tp)
4752
if level == 0 then tp else getQuoteTypeTags.getTagRef(prefix)
4853
case prefix: TermRef if !prefix.symbol.isStatic && level > levelOf(prefix.symbol) =>
49-
dealiasAndTryHeal(prefix.symbol, tp, pos)
54+
tryHeal(prefix.symbol, tp, pos)
5055
case NoPrefix if level > levelOf(tp.symbol) && !tp.typeSymbol.hasAnnotation(defn.QuotedRuntime_SplicedTypeAnnot) =>
51-
dealiasAndTryHeal(tp.symbol, tp, pos)
56+
tryHeal(tp.symbol, tp, pos)
5257
case prefix: ThisType if level > levelOf(prefix.cls) && !tp.symbol.isStatic =>
53-
dealiasAndTryHeal(tp.symbol, tp, pos)
58+
tryHeal(tp.symbol, tp, pos)
5459
case _ =>
5560
mapOver(tp)
5661

@@ -59,11 +64,6 @@ class HealType(pos: SrcPos)(using Context) extends TypeMap {
5964
case (tb: TypeBounds) :: _ => report.error(em"Cannot splice $splice because it is a wildcard type", pos)
6065
case _ =>
6166

62-
private def dealiasAndTryHeal(sym: Symbol, tp: TypeRef, pos: SrcPos): Type =
63-
val tp1 = tp.dealias
64-
if tp1 != tp then apply(tp1)
65-
else tryHeal(tp.symbol, tp, pos)
66-
6767
/** Try to heal reference to type `T` used in a higher level than its definition.
6868
* Returns a reference to a type tag generated by `QuoteTypeTags` that contains a
6969
* reference to a type alias containing the equivalent of `${summon[quoted.Type[T]]}`.

‎tests/pos-macros/i8100b.scala

Lines changed: 37 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,37 @@
1+
import scala.quoted.*
2+
3+
def f[T](using t: Type[T])(using Quotes) =
4+
'{
5+
// @SplicedType type t$1 = t.Underlying
6+
type T2 = T // type T2 = t$1
7+
${
8+
9+
val t0: T = ???
10+
val t1: T2 = ??? // val t1: T = ???
11+
val tp1 = Type.of[T] // val tp1 = t
12+
val tp2 = Type.of[T2] // val tp2 = t
13+
'{
14+
// @SplicedType type t$2 = t.Underlying
15+
val t3: T = ??? // val t3: t$2 = ???
16+
val t4: T2 = ??? // val t4: t$2 = ???
17+
}
18+
}
19+
}
20+
21+
def g(using Quotes) =
22+
'{
23+
type U
24+
type U2 = U
25+
${
26+
27+
val u1: U = ???
28+
val u2: U2 = ??? // val u2: U = ???
29+
30+
val tp1 = Type.of[U] // val tp1 = Type.of[U]
31+
val tp2 = Type.of[U2] // val tp2 = Type.of[U]
32+
'{
33+
val u3: U = ???
34+
val u4: U2 = ??? // val u4: U = ???
35+
}
36+
}
37+
}

‎tests/run-macros/i12392.check

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1 +1 @@
1-
scala.Option[scala.Predef.String] to scala.Option[scala.Int]
1+
scala.Option[java.lang.String] to scala.Option[scala.Int]

‎tests/run-staging/quote-nested-3.check

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,7 @@
11
{
2-
type T = scala.Predef.String
2+
type T = java.lang.String
33
val x: java.lang.String = "foo"
4-
val z: T = x
4+
val z: java.lang.String = x
55

66
(x: java.lang.String)
77
}

‎tests/run-staging/quote-nested-4.check

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
((q: scala.quoted.Quotes) ?=> {
2-
val t: scala.quoted.Type[scala.Predef.String] = scala.quoted.Type.of[scala.Predef.String](q)
2+
val t: scala.quoted.Type[java.lang.String] = scala.quoted.Type.of[java.lang.String](q)
33

4-
(t: scala.quoted.Type[scala.Predef.String])
4+
(t: scala.quoted.Type[java.lang.String])
55
})

‎tests/run-staging/quote-nested-6.check

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,7 @@
11
{
2-
type T[X] = scala.List[X]
2+
type T[X] = [A >: scala.Nothing <: scala.Any] => scala.collection.immutable.List[A][X]
33
val x: java.lang.String = "foo"
4-
val z: T[scala.Predef.String] = scala.List.apply[java.lang.String](x)
4+
val z: [X >: scala.Nothing <: scala.Any] => scala.collection.immutable.List[X][java.lang.String] = scala.List.apply[java.lang.String](x)
55

66
(x: java.lang.String)
77
}

‎tests/run-staging/quote-owners-2.check

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@
22
def ff: scala.Int = {
33
val a: scala.collection.immutable.List[scala.Int] = {
44
type T = scala.collection.immutable.List[scala.Int]
5-
val b: T = scala.Nil.::[scala.Int](3)
5+
val b: scala.collection.immutable.List[scala.Int] = scala.Nil.::[scala.Int](3)
66

77
(b: scala.collection.immutable.List[scala.Int])
88
}

‎tests/run-staging/quote-unrolled-foreach.check

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
}
99
})
1010

11-
((arr: scala.Array[scala.Predef.String], f: scala.Function1[scala.Predef.String, scala.Unit]) => {
11+
((arr: scala.Array[java.lang.String], f: scala.Function1[java.lang.String, scala.Unit]) => {
1212
val size: scala.Int = arr.length
1313
var i: scala.Int = 0
1414
while (i.<(size)) {
@@ -18,7 +18,7 @@
1818
}
1919
})
2020

21-
((arr: scala.Array[scala.Predef.String], f: scala.Function1[scala.Predef.String, scala.Unit]) => {
21+
((arr: scala.Array[java.lang.String], f: scala.Function1[java.lang.String, scala.Unit]) => {
2222
val size: scala.Int = arr.length
2323
var i: scala.Int = 0
2424
while (i.<(size)) {
@@ -41,7 +41,7 @@
4141
((arr: scala.Array[scala.Int], f: scala.Function1[scala.Int, scala.Unit]) => {
4242
val size: scala.Int = arr.length
4343
var i: scala.Int = 0
44-
if (size.%(3).!=(0)) throw new scala.Exception("...") else ()
44+
if (size.%(3).!=(0)) throw new java.lang.Exception("...") else ()
4545
while (i.<(size)) {
4646
f.apply(arr.apply(i))
4747
f.apply(arr.apply(i.+(1)))
@@ -53,7 +53,7 @@
5353
((arr: scala.Array[scala.Int], f: scala.Function1[scala.Int, scala.Unit]) => {
5454
val size: scala.Int = arr.length
5555
var i: scala.Int = 0
56-
if (size.%(4).!=(0)) throw new scala.Exception("...") else ()
56+
if (size.%(4).!=(0)) throw new java.lang.Exception("...") else ()
5757
while (i.<(size)) {
5858
f.apply(arr.apply(i.+(0)))
5959
f.apply(arr.apply(i.+(1)))

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