Parser stack reduction discussion

Check files

6 files changed, 27 insertions, 26 deletions

diff --git a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
index 24e35a9fd8..fa3302b125 100644
--- a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
+++ b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
@@ -759,7 +759,7 @@ self =>
 
     var opstack: List[OpInfo] = Nil
 
-    @deprecated("Use `scala.reflect.internal.Precdence`", "2.11.0")
+    @deprecated("Use `scala.reflect.internal.Precedence`", "2.11.0")
     def precedence(operator: Name): Int = Precedence(operator.toString).level
 
     private def opHead = opstack.head
@@ -1825,7 +1825,6 @@ self =>
         val top = simplePattern(badPattern3)
         val base = opstack
         // See SI-3189, SI-4832 for motivation. Cf SI-3480 for counter-motivation.
-        // TODO: dredge out the remnants of regexp patterns.
         def peekaheadDelim() = {
           def isCloseDelim = in.token match {
             case RBRACE => isXML
@@ -1850,24 +1849,26 @@ self =>
 
       def badPattern3(): Tree = {
         def isComma                = in.token == COMMA
-        def isDelimeter            = in.token == RPAREN || in.token == RBRACE
-        def isCommaOrDelimeter     = isComma || isDelimeter
+        def isDelimiter            = in.token == RPAREN || in.token == RBRACE
+        def isCommaOrDelimiter     = isComma || isDelimiter
         val (isUnderscore, isStar) = opstack match {
           case OpInfo(Ident(nme.WILDCARD), nme.STAR, _) :: _ => (true,   true)
           case OpInfo(_, nme.STAR, _) :: _                   => (false,  true)
           case _                                             => (false, false)
         }
-        def isSeqPatternClose = isUnderscore && isStar && isSequenceOK && isDelimeter
-        val msg = (isUnderscore, isStar, isSequenceOK) match {
-          case (true, true, true) if isComma             => "bad use of _* (a sequence pattern must be the last pattern)"
-          case (true, true, true) if isDelimeter         => "bad brace or paren after _*"
-          case (true, true, false) if isDelimeter        => "bad use of _* (sequence pattern not allowed)"
-          case (false, true, true) if isDelimeter        => "use _* to match a sequence"
-          case (false, true, true) if isCommaOrDelimeter => "trailing * is not a valid pattern"
-          case _                                         => "illegal start of simple pattern"
+        def isSeqPatternClose = isUnderscore && isStar && isSequenceOK && isDelimiter
+        val preamble = "bad simple pattern:"
+        val subtext = (isUnderscore, isStar, isSequenceOK) match {
+          case (true,  true, true)  if isComma            => "bad use of _* (a sequence pattern must be the last pattern)"
+          case (true,  true, true)  if isDelimiter        => "bad brace or paren after _*"
+          case (true,  true, false) if isDelimiter        => "bad use of _* (sequence pattern not allowed)"
+          case (false, true, true)  if isDelimiter        => "use _* to match a sequence"
+          case (false, true, _)     if isCommaOrDelimiter => "trailing * is not a valid pattern"
+          case _                                          => null
         }
+        val msg = if (subtext != null) s"$preamble $subtext" else "illegal start of simple pattern"
         // better recovery if don't skip delims of patterns
-        val skip = !isCommaOrDelimeter || isSeqPatternClose
+        val skip = !isCommaOrDelimiter || isSeqPatternClose
         syntaxErrorOrIncompleteAnd(msg, skip)(errorPatternTree)
       }
 
diff --git a/test/files/neg/t1878.check b/test/files/neg/t1878.check
index ac2071c3d8..5814375515 100644
--- a/test/files/neg/t1878.check
+++ b/test/files/neg/t1878.check
@@ -1,7 +1,7 @@
-t1878.scala:3: error: bad use of _* (a sequence pattern must be the last pattern)
+t1878.scala:3: error: bad simple pattern: bad use of _* (a sequence pattern must be the last pattern)
   val err1 = "" match { case Seq(f @ _*, ',') => f }
                                        ^
-t1878.scala:9: error: bad use of _* (a sequence pattern must be the last pattern)
+t1878.scala:9: error: bad simple pattern: bad use of _* (a sequence pattern must be the last pattern)
   val List(List(_*, arg2), _) = List(List(1,2,3), List(4,5,6))
                   ^
 two errors found
diff --git a/test/files/neg/t3189.check b/test/files/neg/t3189.check
index 3913c526a2..122af56474 100644
--- a/test/files/neg/t3189.check
+++ b/test/files/neg/t3189.check
@@ -1,4 +1,4 @@
-t3189.scala:2: error: use _* to match a sequence
+t3189.scala:2: error: bad simple pattern: use _* to match a sequence
   val Array(a,b*) = ("": Any)
                 ^
 one error found
diff --git a/test/files/neg/t5702-neg-bad-and-wild.check b/test/files/neg/t5702-neg-bad-and-wild.check
index 3970c755bd..ff9e5e5703 100644
--- a/test/files/neg/t5702-neg-bad-and-wild.check
+++ b/test/files/neg/t5702-neg-bad-and-wild.check
@@ -1,4 +1,4 @@
-t5702-neg-bad-and-wild.scala:10: error: bad use of _* (a sequence pattern must be the last pattern)
+t5702-neg-bad-and-wild.scala:10: error: bad simple pattern: bad use of _* (a sequence pattern must be the last pattern)
       case List(1, _*,) => // bad use of _* (a sequence pattern must be the last pattern)
                      ^
 t5702-neg-bad-and-wild.scala:10: error: illegal start of simple pattern
@@ -7,22 +7,22 @@ t5702-neg-bad-and-wild.scala:10: error: illegal start of simple pattern
 t5702-neg-bad-and-wild.scala:12: error: illegal start of simple pattern
       case List(1, _*3,) => // illegal start of simple pattern
                        ^
-t5702-neg-bad-and-wild.scala:14: error: use _* to match a sequence
+t5702-neg-bad-and-wild.scala:14: error: bad simple pattern: use _* to match a sequence
       case List(1, x*) => // use _* to match a sequence
                      ^
-t5702-neg-bad-and-wild.scala:15: error: trailing * is not a valid pattern
+t5702-neg-bad-and-wild.scala:15: error: bad simple pattern: trailing * is not a valid pattern
       case List(x*, 1) => // trailing * is not a valid pattern
                   ^
-t5702-neg-bad-and-wild.scala:16: error: illegal start of simple pattern
+t5702-neg-bad-and-wild.scala:16: error: bad simple pattern: trailing * is not a valid pattern
       case (1, x*) => // trailing * is not a valid pattern
                  ^
-t5702-neg-bad-and-wild.scala:17: error: bad use of _* (sequence pattern not allowed)
+t5702-neg-bad-and-wild.scala:17: error: bad simple pattern: bad use of _* (sequence pattern not allowed)
       case (1, x@_*) => // bad use of _* (sequence pattern not allowed)
                    ^
-t5702-neg-bad-and-wild.scala:23: error: bad use of _* (a sequence pattern must be the last pattern)
+t5702-neg-bad-and-wild.scala:23: error: bad simple pattern: bad use of _* (a sequence pattern must be the last pattern)
     val K(ns @ _*, x) = k // bad use of _* (a sequence pattern must be the last pattern)
                  ^
-t5702-neg-bad-and-wild.scala:24: error: bad use of _* (sequence pattern not allowed)
+t5702-neg-bad-and-wild.scala:24: error: bad simple pattern: bad use of _* (sequence pattern not allowed)
     val (b, _ * ) = Pair(5,6) // bad use of _* (sequence pattern not allowed)
                 ^
 9 errors found
diff --git a/test/files/neg/t5702-neg-bad-xbrace.check b/test/files/neg/t5702-neg-bad-xbrace.check
index d88638aee9..9240abea44 100644
--- a/test/files/neg/t5702-neg-bad-xbrace.check
+++ b/test/files/neg/t5702-neg-bad-xbrace.check
@@ -1,7 +1,7 @@
-t5702-neg-bad-xbrace.scala:19: error: bad brace or paren after _*
+t5702-neg-bad-xbrace.scala:19: error: bad simple pattern: bad brace or paren after _*
           case <year>{_*)}</year> => y
                         ^
-t5702-neg-bad-xbrace.scala:28: error: bad brace or paren after _*
+t5702-neg-bad-xbrace.scala:28: error: bad simple pattern: bad brace or paren after _*
     val <top>{a, z@_*)}</top> = xml
                      ^
 two errors found
diff --git a/test/files/neg/t5702-neg-ugly-xbrace.check b/test/files/neg/t5702-neg-ugly-xbrace.check
index 7d80bbf6be..cdd2438b0e 100644
--- a/test/files/neg/t5702-neg-ugly-xbrace.check
+++ b/test/files/neg/t5702-neg-ugly-xbrace.check
@@ -1,4 +1,4 @@
-t5702-neg-ugly-xbrace.scala:11: error: bad brace or paren after _*
+t5702-neg-ugly-xbrace.scala:11: error: bad simple pattern: bad brace or paren after _*
     val <top>{a, z@_*)</top> = xml
                      ^
 t5702-neg-ugly-xbrace.scala:12: error: Missing closing brace `}' assumed here