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Commit 0776ecb

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lrytzpeteraldous
authored andcommitted
Add an irrefutable version of the NoSuccess extractor (scala#496)
1 parent 7814f37 commit 0776ecb

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2 files changed

+26
-13
lines changed

2 files changed

+26
-13
lines changed

‎shared/src/main/scala/scala/util/parsing/combinator/Parsers.scala‎

Lines changed: 22 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -185,13 +185,34 @@ trait Parsers {
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def get: Nothing = scala.sys.error("No result when parsing failed")
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}
188-
/** An extractor so `NoSuccess(msg, next)` can be used in matches. */
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/**
189+
* An extractor so `case NoSuccess(msg, next)` can be used in matches.
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*
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* Note: On Scala 2.13, using this extractor leads to an exhaustivity warning:
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*
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* {{{
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* def m(r: ParseResult[Int]) = r match {
195+
* case Success(i) => ...
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* case NoSuccess(msg, _) => ... // "warning: match may not be exhaustive"
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* }}}
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*
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* To eliminate this warning, use the irrefutable `NoSuccess.I` extractor.
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* Due to binary compatibility, `NoSuccess` itself cannot be changed.
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*/
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object NoSuccess {
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def unapply[T](x: ParseResult[T]) = x match {
191204
case Failure(msg, next) => Some((msg, next))
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case Error(msg, next) => Some((msg, next))
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case _ => None
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}
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/** An irrefutable version of the `NoSuccess` extractor, used as `case NoSuccess.I(msg, next)`. */
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object I {
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def unapply(x: NoSuccess): Some[(String, Input)] = x match {
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case Failure(msg, next) => Some((msg, next))
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case Error(msg, next) => Some((msg, next))
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}
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}
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}
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/** The failure case of `ParseResult`: contains an error-message and the remaining input.

‎shared/src/test/scala/scala/util/parsing/combinator/PackratParsersTest.scala‎

Lines changed: 4 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -28,9 +28,7 @@ class PackratParsersTest {
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def extractResult(r : ParseResult[Int]): Int = r match {
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case Success(a,_) => a
31-
case NoSuccess(a,_) => sys.error(a)
32-
case Failure(a, _) => sys.error(a)
33-
case Error(a, _) => sys.error(a)
31+
case NoSuccess.I(a,_) => sys.error(a)
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}
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def check(expected: Int, expr: String): Unit = {
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val parseResult = head(new lexical.Scanner(expr))
@@ -84,9 +82,7 @@ class PackratParsersTest {
8482

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def extractResult(r : ParseResult[Int]): Int = r match {
8684
case Success(a,_) => a
87-
case NoSuccess(a,_) => sys.error(a)
88-
case Failure(a, _) => sys.error(a)
89-
case Error(a, _) => sys.error(a)
85+
case NoSuccess.I(a,_) => sys.error(a)
9086
}
9187
def check(expected: Int, expr: String): Unit = {
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val parseResult = head(new lexical.Scanner(expr))
@@ -109,9 +105,7 @@ class PackratParsersTest {
109105
val head = phrase(AnBnCn)
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def extractResult(r: ParseResult[AnBnCnResult]): AnBnCnResult = r match {
111107
case Success(a,_) => a
112-
case NoSuccess(a,_) => sys.error(a)
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case Failure(a, _) => sys.error(a)
114-
case Error(a, _) => sys.error(a)
108+
case NoSuccess.I(a,_) => sys.error(a)
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}
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def threeLists(as: List[Symbol], bs: List[Symbol], cs: List[Symbol]): AnBnCnResult = {
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val as1 = as.map(_.name)
@@ -152,9 +146,7 @@ class PackratParsersTest {
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def extractResult(r: ParseResult[Res]): Res = r match {
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case Success(a,_) => a
155-
case NoSuccess(a,_) => sys.error(a)
156-
case Failure(a, _) => sys.error(a)
157-
case Error(a, _) => sys.error(a)
149+
case NoSuccess.I(a,_) => sys.error(a)
158150
}
159151
def check(expected: Term, input: String, ctx: Ctx): Unit = {
160152
val parseResult = phraseTerm(new lexical.Scanner(input))

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