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Change syntax of cap parameters and members
`cap` is now a soft modifier and we abolish separate cap lists.
1 parent b6bc4b6 commit 5eda51d

21 files changed

+333
-52
lines changed

‎compiler/src/dotty/tools/dotc/ast/untpd.scala

+9-6
Original file line numberDiff line numberDiff line change
@@ -234,6 +234,8 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
234234

235235
case class Tracked()(implicit @constructorOnly src: SourceFile) extends Mod(Flags.Tracked)
236236

237+
case class CaptureParam()(implicit @constructorOnly src: SourceFile) extends Mod(Flags.CaptureParam)
238+
237239
/** Used under pureFunctions to mark impure function types `A => B` in `FunctionWithMods` */
238240
case class Impure()(implicit @constructorOnly src: SourceFile) extends Mod(Flags.Impure)
239241
}
@@ -528,12 +530,13 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
528530
TypeApply(Select(scalaDot(nme.caps), nme.capsOf), tp :: Nil)
529531

530532
// Capture set variable `[C^]` becomes: `[C >: CapSet <: CapSet^{cap}]`
531-
def makeCapsBound()(using Context): TypeBoundsTree =
532-
TypeBoundsTree(
533-
Select(scalaDot(nme.caps), tpnme.CapSet),
534-
makeRetaining(
535-
Select(scalaDot(nme.caps), tpnme.CapSet),
536-
Nil, tpnme.retainsCap))
533+
def makeCapsBound(refsL: List[Tree] = Nil, refsU: List[Tree] = Nil)(using Context): TypeBoundsTree =
534+
val lower = refsL match
535+
case Nil => Select(scalaDot(nme.caps), tpnme.CapSet)
536+
case refsL => makeRetaining(Select(scalaDot(nme.caps), tpnme.CapSet), refsL, tpnme.retains)
537+
val upper =
538+
makeRetaining(Select(scalaDot(nme.caps), tpnme.CapSet), refsU, if refsU.isEmpty then tpnme.retainsCap else tpnme.retains)
539+
TypeBoundsTree(lower, upper)
537540

538541
def makeConstructor(tparams: List[TypeDef], vparamss: List[List[ValDef]], rhs: Tree = EmptyTree)(using Context): DefDef =
539542
DefDef(nme.CONSTRUCTOR, joinParams(tparams, vparamss), TypeTree(), rhs)

‎compiler/src/dotty/tools/dotc/core/Flags.scala

+3
Original file line numberDiff line numberDiff line change
@@ -380,6 +380,9 @@ object Flags {
380380
/** Tracked modifier for class parameter / a class with some tracked parameters */
381381
val (Tracked @ _, _, Dependent @ _) = newFlags(46, "tracked")
382382

383+
/** Cap modifier for capture-set parameters and capture-set members */
384+
val (_, _, CaptureParam @ _) = newFlags(47, "cap")
385+
383386
// ------------ Flags following this one are not pickled ----------------------------------
384387

385388
/** Symbol is not a member of its owner */

‎compiler/src/dotty/tools/dotc/core/StdNames.scala

+1
Original file line numberDiff line numberDiff line change
@@ -443,6 +443,7 @@ object StdNames {
443443
val bytes: N = "bytes"
444444
val canEqual_ : N = "canEqual"
445445
val canEqualAny : N = "canEqualAny"
446+
val cap: N = "cap"
446447
val caps: N = "caps"
447448
val capsOf: N = "capsOf"
448449
val captureChecking: N = "captureChecking"

‎compiler/src/dotty/tools/dotc/parsing/Parsers.scala

+159-32
Original file line numberDiff line numberDiff line change
@@ -35,6 +35,7 @@ import config.SourceVersion.*
3535
import config.SourceVersion
3636
import dotty.tools.dotc.config.MigrationVersion
3737
import dotty.tools.dotc.util.chaining.*
38+
import dotty.tools.dotc.config.Feature.ccEnabled
3839

3940
object Parsers {
4041

@@ -220,6 +221,10 @@ object Parsers {
220221
def isErased = isIdent(nme.erased) && in.erasedEnabled
221222
// Are we seeing an `erased` soft keyword that will not be an identifier?
222223
def isErasedKw = isErased && in.isSoftModifierInParamModifierPosition
224+
// Are we seeing a `cap` soft keyword for declaring a capture-set member or at the beginning a capture-variable parameter list?
225+
def isCapKw = Feature.ccEnabled && isIdent(nme.cap)
226+
// 'cap type' ?
227+
def isCapTypeKw = isCapKw && in.lookahead.token == TYPE
223228
def isSimpleLiteral =
224229
simpleLiteralTokens.contains(in.token)
225230
|| isIdent(nme.raw.MINUS) && numericLitTokens.contains(in.lookahead.token)
@@ -1903,7 +1908,7 @@ object Parsers {
19031908
refinedTypeRest(atSpan(startOffset(t)) {
19041909
RefinedTypeTree(rejectWildcardType(t), refinement(indentOK = true))
19051910
})
1906-
else if Feature.ccEnabled && in.isIdent(nme.UPARROW) && isCaptureUpArrow then
1911+
else if Feature.ccEnabled && in.isIdent(nme.UPARROW) && isCaptureUpArrow then // TODO remove
19071912
atSpan(t.span.start):
19081913
in.nextToken()
19091914
if in.token == LBRACE
@@ -1958,7 +1963,8 @@ object Parsers {
19581963

19591964
def typeBlockStats(): List[Tree] =
19601965
val tdefs = new ListBuffer[Tree]
1961-
while in.token == TYPE do tdefs += typeBlockStat()
1966+
while (in.token == TYPE) do
1967+
tdefs += typeBlockStat()
19621968
tdefs.toList
19631969

19641970
/** TypeBlockStat ::= ‘type’ {nl} TypeDef
@@ -2159,11 +2165,14 @@ object Parsers {
21592165
* NamesAndTypes ::= NameAndType {‘,’ NameAndType}
21602166
* NameAndType ::= id ':' Type
21612167
*/
2162-
def argTypes(namedOK: Boolean, wildOK: Boolean, tupleOK: Boolean): List[Tree] =
2163-
def argType() =
2164-
val t = typ()
2168+
def argTypes(namedOK: Boolean, wildOK: Boolean, tupleOK: Boolean): List[Tree] = //TOOD grammar doc
2169+
def withWildCard(gen: => Tree) =
2170+
val t = gen
21652171
if wildOK then t else rejectWildcardType(t)
21662172

2173+
def argType() = withWildCard(typ())
2174+
def argOrCapType() = withWildCard(if in.token == LBRACE then concreteCapsType(captureSet()) else typ())
2175+
21672176
def namedArgType() =
21682177
atSpan(in.offset):
21692178
val name = ident()
@@ -2174,14 +2183,14 @@ object Parsers {
21742183
atSpan(in.offset):
21752184
val name = ident()
21762185
acceptColon()
2177-
NamedArg(name, argType())
2186+
NamedArg(name, argType()) // TODO allow capsets here?
21782187

2179-
if namedOK && isIdent && in.lookahead.token == EQUALS then
2180-
commaSeparated(() => namedArgType())
2188+
if namedOK && isIdent && in.lookahead.token == EQUALS then // TOOD support for named cap args
2189+
commaSeparated(() => namedArgType())
21812190
else if tupleOK && isIdent && in.lookahead.isColon && sourceVersion.enablesNamedTuples then
21822191
commaSeparated(() => namedElem())
21832192
else
2184-
commaSeparated(() => argType())
2193+
commaSeparated(() => argOrCapType())
21852194
end argTypes
21862195

21872196
def paramTypeOf(core: () => Tree): Tree =
@@ -2240,7 +2249,7 @@ object Parsers {
22402249
inBraces(refineStatSeq())
22412250

22422251
/** TypeBounds ::= [`>:' Type] [`<:' Type]
2243-
* | `^` -- under captureChecking
2252+
* | `^` -- under captureChecking TODO remove
22442253
*/
22452254
def typeBounds(): TypeBoundsTree =
22462255
atSpan(in.offset):
@@ -2250,10 +2259,29 @@ object Parsers {
22502259
else
22512260
TypeBoundsTree(bound(SUPERTYPE), bound(SUBTYPE))
22522261

2262+
/** CaptureSetBounds ::= [`>:' CaptureSetOrRef ] [`<:' CaptureSetOrRef ] --- under captureChecking
2263+
*/
2264+
def captureSetBounds(): TypeBoundsTree =
2265+
atSpan(in.offset):
2266+
TypeBoundsTree(capsBound(SUPERTYPE), capsBound(SUBTYPE))
2267+
22532268
private def bound(tok: Int): Tree =
22542269
if (in.token == tok) { in.nextToken(); toplevelTyp() }
22552270
else EmptyTree
22562271

2272+
private def capsBound(refs: List[Tree], isLowerBound: Boolean = false): Tree =
2273+
if isLowerBound && refs.isEmpty then // lower bounds with empty capture sets become a pure CapSet
2274+
Select(scalaDot(nme.caps), tpnme.CapSet)
2275+
else
2276+
makeRetaining(Select(scalaDot(nme.caps), tpnme.CapSet), refs, if refs.isEmpty then tpnme.retainsCap else tpnme.retains)
2277+
2278+
private def capsBound(tok: Int): Tree =
2279+
if (in.token == tok) then
2280+
in.nextToken()
2281+
capsBound(captureSet(), isLowerBound = tok == SUPERTYPE)
2282+
else
2283+
capsBound(Nil, isLowerBound = tok == SUPERTYPE)
2284+
22572285
/** TypeAndCtxBounds ::= TypeBounds [`:` ContextBounds]
22582286
*/
22592287
def typeAndCtxBounds(pname: TypeName): Tree = {
@@ -2263,6 +2291,15 @@ object Parsers {
22632291
else atSpan((t.span union cbs.head.span).start) { ContextBounds(t, cbs) }
22642292
}
22652293

2294+
/** CaptureSetAndCtxBounds ::= CaptureSetBounds [`:` ContextBounds] -- under captureChecking
2295+
*/
2296+
def captureSetAndCtxBounds(pname: TypeName): Tree = {
2297+
val t = captureSetBounds()
2298+
val cbs = contextBounds(pname)
2299+
if (cbs.isEmpty) t
2300+
else atSpan((t.span union cbs.head.span).start) { ContextBounds(t, cbs) }
2301+
}
2302+
22662303
/** ContextBound ::= Type [`as` id] */
22672304
def contextBound(pname: TypeName): Tree =
22682305
val t = toplevelTyp(inContextBound = true)
@@ -2782,7 +2819,10 @@ object Parsers {
27822819
in.nextToken()
27832820
simpleExprRest(selectorOrMatch(t), location, canApply = true)
27842821
case LBRACKET =>
2785-
val tapp = atSpan(startOffset(t), in.offset) { TypeApply(t, typeArgs(namedOK = true, wildOK = false)) }
2822+
val tapp = atSpan(startOffset(t), in.offset) {
2823+
val args = typeArgs(namedOK = true, wildOK = false)
2824+
TypeApply(t, args)
2825+
}
27862826
simpleExprRest(tapp, location, canApply = true)
27872827
case LPAREN | LBRACE | INDENT if canApply =>
27882828
val app = atSpan(startOffset(t), in.offset) { mkApply(t, argumentExprs()) }
@@ -3305,6 +3345,7 @@ object Parsers {
33053345
case nme.transparent => Mod.Transparent()
33063346
case nme.infix => Mod.Infix()
33073347
case nme.tracked => Mod.Tracked()
3348+
case nme.cap => Mod.CaptureParam()
33083349
}
33093350
}
33103351

@@ -3372,7 +3413,7 @@ object Parsers {
33723413
* | override
33733414
* | opaque
33743415
* LocalModifier ::= abstract | final | sealed | open | implicit | lazy | erased |
3375-
* inline | transparent | infix
3416+
* inline | transparent | infix | cap
33763417
*/
33773418
def modifiers(allowed: BitSet = modifierTokens, start: Modifiers = Modifiers()): Modifiers = {
33783419
@tailrec
@@ -3461,7 +3502,6 @@ object Parsers {
34613502
recur(numLeadParams, firstClause = true, prevIsTypeClause = false)
34623503
end typeOrTermParamClauses
34633504

3464-
34653505
/** ClsTypeParamClause::= ‘[’ ClsTypeParam {‘,’ ClsTypeParam} ‘]’
34663506
* ClsTypeParam ::= {Annotation} [‘+’ | ‘-’]
34673507
* id [HkTypeParamClause] TypeAndCtxBounds
@@ -3486,6 +3526,43 @@ object Parsers {
34863526
in.nextToken()
34873527
ok
34883528

3529+
def ensureNoHKParams() = // for cap params
3530+
if in.token == LBRACKET then
3531+
syntaxError(em"'cap' parameters cannot have type parameters")
3532+
in.nextToken()
3533+
3534+
def ensureNoVariance() = // for cap params
3535+
if isIdent(nme.raw.PLUS) || isIdent(nme.raw.MINUS) then
3536+
syntaxError(em"no `+/-` variance annotation allowed here")
3537+
in.nextToken()
3538+
3539+
def typeOrCapParam(): TypeDef =
3540+
if isCapKw then
3541+
in.nextToken()
3542+
capParam()
3543+
else typeParam()
3544+
3545+
def capParam(): TypeDef = {
3546+
val start = in.offset
3547+
var mods = annotsAsMods() | Param
3548+
if paramOwner.isClass then
3549+
mods |= PrivateLocal
3550+
ensureNoVariance() // TODO: in the future, we might want to support variances on capture params, ruled out for now
3551+
atSpan(start, nameStart) {
3552+
val name =
3553+
if paramOwner.acceptsWildcard && in.token == USCORE then
3554+
in.nextToken()
3555+
WildcardParamName.fresh().toTypeName
3556+
else ident().toTypeName
3557+
ensureNoHKParams()
3558+
val bounds =
3559+
if paramOwner.acceptsCtxBounds then captureSetAndCtxBounds(name)
3560+
else if sourceVersion.enablesNewGivens && paramOwner == ParamOwner.Type then captureSetAndCtxBounds(name)
3561+
else captureSetBounds()
3562+
TypeDef(name, bounds).withMods(mods)
3563+
}
3564+
}
3565+
34893566
def typeParam(): TypeDef = {
34903567
val start = in.offset
34913568
var mods = annotsAsMods() | Param
@@ -3509,11 +3586,14 @@ object Parsers {
35093586
TypeDef(name, lambdaAbstract(hkparams, bounds)).withMods(mods)
35103587
}
35113588
}
3512-
commaSeparated(() => typeParam())
3589+
commaSeparated(() => typeOrCapParam())
35133590
}
35143591

35153592
def typeParamClauseOpt(paramOwner: ParamOwner): List[TypeDef] =
3516-
if (in.token == LBRACKET) typeParamClause(paramOwner) else Nil
3593+
if (in.token == LBRACKET)
3594+
typeParamClause(paramOwner)
3595+
else
3596+
Nil
35173597

35183598
/** ContextTypes ::= FunArgType {‘,’ FunArgType}
35193599
*/
@@ -3855,25 +3935,29 @@ object Parsers {
38553935
* | var VarDef
38563936
* | def DefDef
38573937
* | type {nl} TypeDef
3938+
* | cap type {nl} CapDef -- under capture checking
38583939
* | TmplDef
38593940
* EnumCase ::= `case' (id ClassConstr [`extends' ConstrApps]] | ids)
38603941
*/
3861-
def defOrDcl(start: Int, mods: Modifiers): Tree = in.token match {
3862-
case VAL =>
3863-
in.nextToken()
3864-
patDefOrDcl(start, mods)
3865-
case VAR =>
3866-
val mod = atSpan(in.skipToken()) { Mod.Var() }
3867-
val mod1 = addMod(mods, mod)
3868-
patDefOrDcl(start, mod1)
3869-
case DEF =>
3870-
defDefOrDcl(start, in.skipToken(mods))
3871-
case TYPE =>
3872-
typeDefOrDcl(start, in.skipToken(mods))
3873-
case CASE if inEnum =>
3874-
enumCase(start, mods)
3875-
case _ =>
3876-
tmplDef(start, mods)
3942+
def defOrDcl(start: Int, mods: Modifiers): Tree =
3943+
in.token match {
3944+
case VAL =>
3945+
in.nextToken()
3946+
patDefOrDcl(start, mods)
3947+
case VAR =>
3948+
val mod = atSpan(in.skipToken()) { Mod.Var() }
3949+
val mod1 = addMod(mods, mod)
3950+
patDefOrDcl(start, mod1)
3951+
case DEF =>
3952+
defDefOrDcl(start, in.skipToken(mods))
3953+
case TYPE if mods.is(CaptureParam) =>
3954+
capDefOrDcl(start, in.skipToken(mods))
3955+
case TYPE =>
3956+
typeDefOrDcl(start, in.skipToken(mods))
3957+
case CASE if inEnum =>
3958+
enumCase(start, mods)
3959+
case _ =>
3960+
tmplDef(start, mods)
38773961
}
38783962

38793963
/** PatDef ::= ids [‘:’ Type] [‘=’ Expr]
@@ -4082,6 +4166,43 @@ object Parsers {
40824166
}
40834167
}
40844168

4169+
private def concreteCapsType(refs: List[Tree]): Tree =
4170+
makeRetaining(Select(scalaDot(nme.caps), tpnme.CapSet), refs, tpnme.retains)
4171+
4172+
/** CapDef ::= id CaptureSetAndCtxBounds [‘=’ CaptureSetOrRef] -- under capture checking
4173+
*/
4174+
def capDefOrDcl(start: Offset, mods: Modifiers): Tree =
4175+
newLinesOpt()
4176+
atSpan(start, nameStart) {
4177+
val nameIdent = typeIdent()
4178+
val tname = nameIdent.name.asTypeName
4179+
if in.token == LBRACKET then syntaxError(em"'cap type' declarations cannot have type parameters")
4180+
4181+
def makeCapDef(refs: List[Tree] | Tree): Tree = {
4182+
val tdef = TypeDef(nameIdent.name.toTypeName,
4183+
refs.match
4184+
case refs: List[Tree] => concreteCapsType(refs)
4185+
case bounds: Tree => bounds)
4186+
4187+
if (nameIdent.isBackquoted)
4188+
tdef.pushAttachment(Backquoted, ())
4189+
finalizeDef(tdef, mods, start)
4190+
}
4191+
4192+
in.token.match
4193+
case EQUALS =>
4194+
in.nextToken()
4195+
makeCapDef(captureSet())
4196+
case SUBTYPE | SUPERTYPE | SEMI | NEWLINE | NEWLINES | COMMA | RBRACE | OUTDENT | EOF =>
4197+
makeCapDef(captureSetAndCtxBounds(tname))
4198+
case _ if (staged & StageKind.QuotedPattern) != 0
4199+
|| sourceVersion.enablesNewGivens && in.isColon =>
4200+
makeCapDef(captureSetAndCtxBounds(tname))
4201+
case _ =>
4202+
syntaxErrorOrIncomplete(ExpectedCaptureBoundOrEquals(in.token))
4203+
return EmptyTree // return to avoid setting the span to EmptyTree
4204+
}
4205+
40854206
/** TmplDef ::= ([‘case’] ‘class’ | ‘trait’) ClassDef
40864207
* | [‘case’] ‘object’ ObjectDef
40874208
* | ‘enum’ EnumDef
@@ -4675,6 +4796,7 @@ object Parsers {
46754796
* | ‘var’ VarDef
46764797
* | ‘def’ DefDef
46774798
* | ‘type’ {nl} TypeDef
4799+
* | ‘cap’ ‘type’ {nl} CapDef -- under capture checking
46784800
* (in reality we admit class defs and vars and filter them out afterwards in `checkLegal`)
46794801
*/
46804802
def refineStatSeq(): List[Tree] = {
@@ -4699,9 +4821,14 @@ object Parsers {
46994821
fail(em"this kind of definition cannot be a refinement")
47004822

47014823
while
4824+
val mods =
4825+
if isCapTypeKw then // allow `cap type` in refinements
4826+
in.nextToken()
4827+
addMod(Modifiers(), Mod.CaptureParam())
4828+
else Modifiers()
47024829
val dclFound = isDclIntro
47034830
if dclFound then
4704-
stats ++= checkLegal(defOrDcl(in.offset, Modifiers()))
4831+
stats ++= checkLegal(defOrDcl(in.offset, mods))
47054832
var what = "declaration"
47064833
if inFunReturnType then what += " (possible cause: missing `=` in front of current method body)"
47074834
statSepOrEnd(stats, noPrevStat = !dclFound, what)

‎compiler/src/dotty/tools/dotc/parsing/Scanners.scala

+1-1
Original file line numberDiff line numberDiff line change
@@ -1209,7 +1209,7 @@ object Scanners {
12091209

12101210
def isSoftModifier: Boolean =
12111211
token == IDENTIFIER
1212-
&& (softModifierNames.contains(name) || name == nme.erased && erasedEnabled || name == nme.tracked && trackedEnabled)
1212+
&& (softModifierNames.contains(name) || name == nme.erased && erasedEnabled || name == nme.tracked && trackedEnabled || name == nme.cap && Feature.ccEnabled)
12131213

12141214
def isSoftModifierInModifierPosition: Boolean =
12151215
isSoftModifier && inModifierPosition()

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