refactor parser entry points and extract a few methods out

This commit contains three logical changes:

1. Split `templateStatSeq` into two methods as we need more reliable
   parsing of template body alone for new `parseStats` entry point.

2. Add new parser entry point called `parseStats` which is aimed towards
   use in tools that require parsing of Scala code that can be written
   inside of a template.

   Such functionality is required for parsing lines in repl, parsing
   code through toolbox, parsing and running scala scripts and lastly
   for quasiquotes. All of them are refactored to use this very method
   in the next commits.

   A new method called `templateStatsCompat` is also added to make this
   commit pass the tests but it's a temporary hack that will be removed
   in next commit in favor of `parseStats`.

3. Extract out a few methods like `isCaseDefStart`, `expectedMsgTemplate`
   and `parseRule`. These are needed to override parser behaviour in
   updated quasiquotes parser (see next commits).

3 files changed, 48 insertions, 32 deletions

diff --git a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
index d0b0c09d59..6a10f2dd10 100644
--- a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
+++ b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
@@ -334,22 +334,27 @@ self =>
 
     def parseStartRule: () => Tree
 
-    /** This is the general parse entry point.
-     */
-    def parse(): Tree = {
-      val t = parseStartRule()
+    def parseRule[T](rule: this.type => T): T = {
+      val t = rule(this)
       accept(EOF)
       t
     }
 
+    /** This is the general parse entry point.
+     */
+    def parse(): Tree = parseRule(_.parseStartRule())
+
+    /** This is alternative entry point for repl, script runner, toolbox and quasiquotes.
+     */
+    def parseStats(): List[Tree] = parseRule(_.templateStats())
+
     /** This is the parse entry point for code which is not self-contained, e.g.
      *  a script which is a series of template statements.  They will be
      *  swaddled in Trees until the AST is equivalent to the one returned
      *  by compilationUnit().
      */
     def scriptBody(): Tree = {
-      val stmts = templateStats()
-      accept(EOF)
+      val stmts = parseStats()
 
       def mainModuleName = newTermName(settings.script.value)
       /* If there is only a single object template in the file and it has a
@@ -563,8 +568,8 @@ self =>
       and
     }
 
-    def expectedMsg(token: Int): String =
-      token2string(token) + " expected but " +token2string(in.token) + " found."
+    def expectedMsgTemplate(exp: String, fnd: String) = s"$exp expected but $fnd found."
+    def expectedMsg(token: Int): String = expectedMsgTemplate(token2string(token), token2string(in.token))
 
     /** Consume one token of the specified type, or signal an error if it is not there. */
     def accept(token: Int): Int = {
@@ -627,6 +632,8 @@ self =>
 
     def isAnnotation: Boolean = in.token == AT
 
+    def isCaseDefStart: Boolean = in.token == CASE
+
     def isLocalModifier: Boolean = in.token match {
       case ABSTRACT | FINAL | SEALED | IMPLICIT | LAZY => true
       case _ => false
@@ -1298,7 +1305,7 @@ self =>
               in.nextToken()
               if (in.token != LBRACE) catchFromExpr()
               else inBracesOrNil {
-                if (in.token == CASE) caseClauses()
+                if (isCaseDefStart) caseClauses()
                 else catchFromExpr()
               }
             }
@@ -1613,7 +1620,7 @@ self =>
      */
     def blockExpr(): Tree = atPos(in.offset) {
       inBraces {
-        if (in.token == CASE) Match(EmptyTree, caseClauses())
+        if (isCaseDefStart) Match(EmptyTree, caseClauses())
         else block()
       }
     }
@@ -2605,7 +2612,7 @@ self =>
           case EQUALS =>
             in.nextToken()
             TypeDef(mods, name, tparams, typ())
-          case SUPERTYPE | SUBTYPE | SEMI | NEWLINE | NEWLINES | COMMA | RBRACE =>
+          case t if t == SUPERTYPE || t == SUBTYPE || t == COMMA || t == RBRACE || isStatSep(t) =>
             TypeDef(mods | Flags.DEFERRED, name, tparams, typeBounds())
           case _ =>
             syntaxErrorOrIncompleteAnd("`=', `>:', or `<:' expected", skipIt = true)(EmptyTree)
@@ -2906,27 +2913,14 @@ self =>
       stats.toList
     }
 
-    /** Informal - for the repl and other direct parser accessors.
-     */
-    def templateStats(): List[Tree] = templateStatSeq(isPre = false)._2 match {
-      case Nil    => EmptyTree.asList
-      case stats  => stats
-    }
-
     /** {{{
-     *  TemplateStatSeq  ::= [id [`:' Type] `=>'] TemplateStat {semi TemplateStat}
-     *  TemplateStat     ::= Import
-     *                     | Annotations Modifiers Def
-     *                     | Annotations Modifiers Dcl
-     *                     | Expr1
-     *                     | super ArgumentExprs {ArgumentExprs}
-     *                     |
+     *  TemplateStatSeq  ::= [id [`:' Type] `=>'] TemplateStats
      *  }}}
      * @param isPre specifies whether in early initializer (true) or not (false)
      */
     def templateStatSeq(isPre : Boolean): (ValDef, List[Tree]) = checkNoEscapingPlaceholders {
       var self: ValDef = emptyValDef
-      val stats = new ListBuffer[Tree]
+      var firstOpt: Option[Tree] = None
       if (isExprIntro) {
         in.flushDoc
         val first = expr(InTemplate) // @S: first statement is potentially converted so cannot be stubbed.
@@ -2943,10 +2937,25 @@ self =>
           }
           in.nextToken()
         } else {
-          stats += first
+          firstOpt = Some(first)
           acceptStatSepOpt()
         }
       }
+      (self, firstOpt ++: templateStats())
+    }
+
+    /** {{{
+     *  TemplateStats    ::= TemplateStat {semi TemplateStat}
+     *  TemplateStat     ::= Import
+     *                     | Annotations Modifiers Def
+     *                     | Annotations Modifiers Dcl
+     *                     | Expr1
+     *                     | super ArgumentExprs {ArgumentExprs}
+     *                     |
+     *  }}}
+     */
+    def templateStats(): List[Tree] = {
+      val stats = new ListBuffer[Tree]
       while (!isStatSeqEnd) {
         if (in.token == IMPORT) {
           in.flushDoc
@@ -2961,7 +2970,14 @@ self =>
         }
         acceptStatSepOpt()
       }
-      (self, stats.toList)
+      stats.toList
+    }
+
+    /** Informal - for the repl and other direct parser accessors.
+     */
+    def templateStatsCompat(): List[Tree] = templateStats() match {
+      case Nil => EmptyTree.asList
+      case stats => stats
     }
 
     /** {{{
@@ -3026,14 +3042,14 @@ self =>
      */
     def blockStatSeq(): List[Tree] = checkNoEscapingPlaceholders {
       val stats = new ListBuffer[Tree]
-      while (!isStatSeqEnd && in.token != CASE) {
+      while (!isStatSeqEnd && !isCaseDefStart) {
         if (in.token == IMPORT) {
           stats ++= importClause()
           acceptStatSep()
         }
         else if (isExprIntro) {
           stats += statement(InBlock)
-          if (in.token != RBRACE && in.token != CASE) acceptStatSep()
+          if (in.token != RBRACE && !isCaseDefStart) acceptStatSep()
         }
         else if (isDefIntro || isLocalModifier || isAnnotation) {
           if (in.token == IMPLICIT) {
diff --git a/src/repl/scala/tools/nsc/interpreter/ExprTyper.scala b/src/repl/scala/tools/nsc/interpreter/ExprTyper.scala
index 9353215e1e..e79fc310bb 100644
--- a/src/repl/scala/tools/nsc/interpreter/ExprTyper.scala
+++ b/src/repl/scala/tools/nsc/interpreter/ExprTyper.scala
@@ -28,7 +28,7 @@ trait ExprTyper {
 
       result
     }
-    def stmts(code: String) = applyRule(code, _.templateStats())
+    def stmts(code: String) = applyRule(code, _.templateStatsCompat())
   }
 
   /** Parse a line into a sequence of trees. Returns None if the input is incomplete. */
diff --git a/src/repl/scala/tools/nsc/interpreter/JLineCompletion.scala b/src/repl/scala/tools/nsc/interpreter/JLineCompletion.scala
index 8b8b668c9f..8c5162d788 100644
--- a/src/repl/scala/tools/nsc/interpreter/JLineCompletion.scala
+++ b/src/repl/scala/tools/nsc/interpreter/JLineCompletion.scala
@@ -190,7 +190,7 @@ class JLineCompletion(val intp: IMain) extends Completion with CompletionOutput
 
   // literal Ints, Strings, etc.
   object literals extends CompletionAware {
-    def simpleParse(code: String): Tree = newUnitParser(code).templateStats().last
+    def simpleParse(code: String): Tree = newUnitParser(code).templateStatsCompat().last
     def completions(verbosity: Int) = Nil
 
     override def follow(id: String) = simpleParse(id) match {