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Fix loop in parser #15421

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merged 2 commits into from
Jun 13, 2022
Merged

Fix loop in parser #15421

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ed658ee
Fix loop in parser
odersky Jun 11, 2022
59556fd
Defensive code to make sure there's no infinite loop in `skip`.
odersky Jun 11, 2022
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15 changes: 7 additions & 8 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 @@ -2745,14 +2745,13 @@ object Parsers {
def pattern3(): Tree =
val p = infixPattern()
if followingIsVararg() then
atSpan(in.skipToken()) {
p match
case p @ Ident(name) if name.isVarPattern =>
Typed(p, Ident(tpnme.WILDCARD_STAR))
case _ =>
syntaxError(em"`*` must follow pattern variable")
p
}
val start = in.skipToken()
p match
case p @ Ident(name) if name.isVarPattern =>
Typed(p, atSpan(start) { Ident(tpnme.WILDCARD_STAR) })
case _ =>
syntaxError(em"`*` must follow pattern variable", start)
p
else p

/** Pattern2 ::= [id `@'] Pattern3
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7 changes: 6 additions & 1 deletion compiler/src/dotty/tools/dotc/parsing/Scanners.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -313,8 +313,13 @@ object Scanners {
// when skipping and therefore might erroneously end up syncing on a nested OUTDENT.
if debugTokenStream then
println(s"\nSTART SKIP AT ${sourcePos().line + 1}, $this in $currentRegion")
while !atStop do
var noProgress = 0
// Defensive measure to ensure we always get out of the following while loop
// even if source file is weirly formatted (i.e. we never reach EOF
while !atStop && noProgress < 3 do
val prevOffset = offset
nextToken()
if offset == prevOffset then noProgress += 1 else noProgress = 0
if debugTokenStream then
println(s"\nSTOP SKIP AT ${sourcePos().line + 1}, $this in $currentRegion")
if token == OUTDENT then dropUntil(_.isInstanceOf[Indented])
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