Revert "Better prediction after with in types"

This reverts commit 95437d1.

Author: odersky

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -920,16 +920,6 @@ object Parsers {
       val next = in.lookahead.token
       next == LBRACKET || next == LPAREN
 
-    private def withEndMigrationWarning(): Boolean =
-      migrateTo3
-      && {
-        warning(
-          em"""In Scala 3, `with` at the end of a line will start definitions,
-              |so it cannot be used in front of a parent constructor anymore.
-              |Place the `with` at the beginning of the next line instead.""")
-        true
-      }
-
     /** Does a template start after `with`? This is the case if either
      *   - the next token is `{`
      *   - the `with` is at the end of a line
@@ -941,7 +931,17 @@ object Parsers {
       val lookahead = in.LookaheadScanner()
       lookahead.nextToken()
       lookahead.token == LBRACE
-      || lookahead.isAfterLineEnd && !withEndMigrationWarning()
+      || lookahead.isAfterLineEnd
+          && {
+            if migrateTo3 then
+              warning(
+                em"""In Scala 3, `with` at the end of a line will start definitions,
+                    |so it cannot be used in front of a parent constructor anymore.
+                    |Place the `with` at the beginning of the next line instead.""")
+              false
+            else
+              true
+          }
       || (lookahead.isIdent || lookahead.token == THIS)
           && {
             lookahead.nextToken()
@@ -953,20 +953,6 @@ object Parsers {
             || lookahead.token == ARROW
           }
 
-    /** Does a refinement start after `with`? This is the case if either
-     *   - the next token is `{`
-     *   - the `with` is at the end of a line and is followed by a token that starts a declaration
-     */
-    def followingIsRefinementStart() =
-      val lookahead = in.LookaheadScanner()
-      lookahead.nextToken()
-      lookahead.token == LBRACE
-      || lookahead.isAfterLineEnd
-         && {
-           if lookahead.token == INDENT then lookahead.nextToken()
-           dclIntroTokens.contains(lookahead.token)
-         }
-
 /* --------- OPERAND/OPERATOR STACK --------------------------------------- */
 
     var opStack: List[OpInfo] = Nil
@@ -1598,8 +1584,11 @@ object Parsers {
     def withType(): Tree = withTypeRest(annotType())
 
     def withTypeRest(t: Tree): Tree =
-      if in.token == WITH && !followingIsRefinementStart() then
-        in.nextTokenNoIndent()
+      def isRefinementStart =
+        val la = in.lookahead
+        la.isAfterLineEnd || la.token == LBRACE
+      if in.token == WITH && !isRefinementStart then
+        in.nextToken()
         if sourceVersion.isAtLeast(`3.1`) then
           deprecationWarning(DeprecatedWithOperator())
         atSpan(startOffset(t)) { makeAndType(t, withType()) }
@@ -3869,7 +3858,8 @@ object Parsers {
               if (name != nme.ERROR)
                 self = makeSelfDef(name, tpt).withSpan(first.span)
           }
-          in.nextTokenNoIndent()
+          in.token = SELFARROW // suppresses INDENT insertion after `=>`
+          in.nextToken()
         }
         else {
           stats += first

compiler/src/dotty/tools/dotc/parsing/Scanners.scala

@@ -323,11 +323,6 @@ object Scanners {
       printState()
     }
 
-    /** Like nextToken, but don't insert indent characters afterwards */
-    def nextTokenNoIndent(): Unit =
-      token = EMPTY // this will suppress newline and indent insertion
-      nextToken()
-
     final def printState() =
       if debugTokenStream && (showLookAheadOnDebug || !isInstanceOf[LookaheadScanner]) then
         print(s"[$show${if isInstanceOf[LookaheadScanner] then "(LA)" else ""}]")
@@ -498,6 +493,8 @@ object Scanners {
           if canStartIndentTokens.contains(lastToken) then
             currentRegion = Indented(nextWidth, Set(), lastToken, currentRegion)
             insert(INDENT, offset)
+          else if lastToken == SELFARROW then
+            currentRegion.knownWidth = nextWidth
         else if (lastWidth != nextWidth)
           errorButContinue(spaceTabMismatchMsg(lastWidth, nextWidth))
       currentRegion match {

compiler/src/dotty/tools/dotc/parsing/Tokens.scala

@@ -204,6 +204,7 @@ object Tokens extends TokensCommon {
   final val QUOTE = 87;            enter(QUOTE, "'")
 
   final val COLONEOL = 88;         enter(COLONEOL, ":", ": at eol")
+  final val SELFARROW = 89;        enter(SELFARROW, "=>") // reclassified ARROW following self-type
 
   /** XML mode */
   final val XMLSTART = 99;         enter(XMLSTART, "$XMLSTART$<") // TODO: deprecate

tests/neg/with-template.scala

@@ -11,10 +11,4 @@ object Test2 extends A with
     println("foo")
   }
 
-def foo: A with
-  B with
-  C = ???
-
-
-