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Fix #4058: reject sealed and lazy for class parameters in parser #4070

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Fix #4058: reject sealed and lazy for class parameters in parser #4070

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9172a96
Fix #4058: reject sealed and lazy for class parameters in parser
Blaisorblade Mar 4, 2018
8a79276
Add omitted @tailrec annotation (mostly for clarity)
Blaisorblade Mar 4, 2018
6299785
Test a few extra variants
Blaisorblade Mar 4, 2018
1d85ac7
Don't special-case `sealed`
Blaisorblade Mar 5, 2018
6f2effe
Update grammar in comment to follow code
Blaisorblade Mar 5, 2018
f4b3538
Report forbidden modifiers from modifiers
Blaisorblade Mar 5, 2018
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25 changes: 19 additions & 6 deletions compiler/src/dotty/tools/dotc/parsing/Parsers.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1650,6 +1650,7 @@ object Parsers {
case PROTECTED => Mod.Protected()
case SEALED => Mod.Sealed()
}
private def flagsOfModToken(tok: Int): FlagSet = modOfToken(tok).flags

/** Drop `private' modifier when followed by a qualifier.
* Contract `abstract' and `override' to ABSOVERRIDE
Expand Down Expand Up @@ -1705,7 +1706,14 @@ object Parsers {
}
} else mods

/** {Annotation} {Modifier}
/**
* Extend the start Modifiers by parsing modifier tokens in the allowed BitSet, appearing in any order.
* Ignore modifier tokens in the parsedSeparately BitSet, so that the caller can parse them after modifier returns
* (suitable to parse `AllowedModifiers* lazy`).
* Report modifier tokens that appear neither in allowed nor in parsedSeparately.
*
* Grammar:
* {Annotation} {Modifier}
* Modifiers ::= {Modifier}
* LocalModifiers ::= {LocalModifier}
* AccessModifier ::= (private | protected) [AccessQualifier]
Expand All @@ -1714,7 +1722,7 @@ object Parsers {
* | override
* LocalModifier ::= abstract | final | sealed | implicit | lazy
*/
def modifiers(allowed: BitSet = modifierTokens, start: Modifiers = Modifiers()): Modifiers = {
def modifiers(allowed: BitSet = modifierTokens, start: Modifiers = Modifiers(), parsedSeparately: BitSet = BitSet.empty): Modifiers = {
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I am not convinced by this change of API. If the caller wants to parse some modifier separately, then he can exclude them from the allowed modifiers.

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To get the nicer error I need to distinguish "not allowed" (which gives an error) from "parsed separately" (which doesn't). I had to use parsedSeparately only once.

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If the API is too hard for the error, I can revert/separate these refactorings.

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I think a better API would something along the line of:

/** ...
 *  @param errorOn emit a syntax error when a parsed modifier is in errorOn
 */
def modifiers(allowed: BitSet, start: Modifiers, errorOn: BitSet) = {
  ...
  if (allowed.contains(in.token) { ...; loop() }
  else if (errorOn.contains(in.token) { syntaxError; loop() }
  else ...
}

You can keep parsing modifiers after encountering an invalid modifier.

But since it is used only once, I think we should no complicate this API.

@tailrec
def loop(mods: Modifiers): Modifiers = {
if (allowed contains in.token) {
Expand All @@ -1725,6 +1733,8 @@ object Parsers {
in.nextToken()
loop(mods)
} else {
if ((modifierTokens contains in.token) && !(parsedSeparately contains in.token))
syntaxError(hl"Modifier `${flagsOfModToken(in.token)}' not allowed at this position")
mods
}
}
Expand Down Expand Up @@ -1839,7 +1849,10 @@ object Parsers {
val start = in.offset
var mods = annotsAsMods()
if (owner.isTypeName) {
mods = modifiers(start = mods) | ParamAccessor
// Adding ParamAccessor would crash
mods = modifiers(start = mods, allowed = modifierTokens - SEALED) | ParamAccessor
if (mods.is(Lazy))
syntaxError("`lazy' modifier not allowed here. Use call-by-name parameters instead")
mods =
atPos(start, in.offset) {
if (in.token == VAL) {
Expand Down Expand Up @@ -1879,7 +1892,7 @@ object Parsers {
def paramClause(): List[ValDef] = inParens {
if (in.token == RPAREN) Nil
else {
def funArgMods(): Unit = {
@tailrec def funArgMods(): Unit = {
if (in.token == IMPLICIT) {
implicitOffset = in.offset
imods = addMod(imods, atPos(accept(IMPLICIT)) { Mod.Implicit() })
Expand Down Expand Up @@ -2451,7 +2464,7 @@ object Parsers {

/** BlockStatSeq ::= { BlockStat semi } [ResultExpr]
* BlockStat ::= Import
* | Annotations [implicit] [lazy] Def
* | Annotations [implicit] [erased] [lazy] Def
* | Annotations LocalModifiers TmplDef
* | Expr1
* |
Expand All @@ -2468,7 +2481,7 @@ object Parsers {
else if (isDefIntro(localModifierTokens))
if (in.token == IMPLICIT || in.token == ERASED) {
val start = in.offset
var imods = modifiers(funArgMods)
var imods = modifiers(funArgMods, parsedSeparately = BitSet(LAZY))
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I don't think we need this, the current error message is good:

72 |  lazy def bar = 1
   |           ^
   |           modifier `lazy` is not allowed for this definition

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That’s not the error message I’m fixing. Will separate the PR and add examples.

if (isBindingIntro) stats += implicitClosure(start, Location.InBlock, imods)
else stats +++= localDef(start, imods)
} else {
Expand Down
9 changes: 9 additions & 0 deletions tests/neg/i4058.scala
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@@ -0,0 +1,9 @@
class A(sealed val a: Int) // error
class B(lazy val a: Int) // error
class C(abstract val a: Int) // error
class D {
def f(sealed a: Int) = 0 // error
def g(lazy a: Int) = 0 // error
def g(override a: Int) = 0 // error
def g(abstract a: Int) = 0 // error
}