Fix #2334: Require at least one digit after '.' in floating point literals

Author: odersky

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

@@ -120,7 +120,7 @@ abstract class CharArrayReader { self =>
   def isAtEnd = charOffset >= buf.length
 
   /** A new reader that takes off at the current character position */
-  def lookaheadReader = new CharArrayLookaheadReader
+  def lookaheadReader() = new CharArrayLookaheadReader
 
   class CharArrayLookaheadReader extends CharArrayReader {
     val buf = self.buf

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

@@ -180,7 +180,7 @@ object Scanners {
     private[this] var docstringMap: SortedMap[Int, Comment] = SortedMap.empty
 
     private[this] def addComment(comment: Comment): Unit = {
-      val lookahead = lookaheadReader
+      val lookahead = lookaheadReader()
       def nextPos: Int = (lookahead.getc(): @switch) match {
         case ' ' | '\t' => nextPos
         case CR | LF | FF =>
@@ -863,7 +863,7 @@ object Scanners {
         nextChar()
       }
       if (ch == 'e' || ch == 'E') {
-        val lookahead = lookaheadReader
+        val lookahead = lookaheadReader()
         lookahead.nextChar()
         if (lookahead.ch == '+' || lookahead.ch == '-') {
           lookahead.nextChar()
@@ -907,36 +907,10 @@ object Scanners {
       }
       token = INTLIT
       if (base == 10 && ch == '.') {
-        val isDefinitelyNumber = {
-          val lookahead = lookaheadReader
-          val c = lookahead.getc()
-          (c: @switch) match {
-            /** Another digit is a giveaway. */
-            case '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' =>
-              true
-
-            /** Backquoted idents like 22.`foo`. */
-            case '`' =>
-              false
-
-            /** These letters may be part of a literal, or a method invocation on an Int.
-             */
-            case 'd' | 'D' | 'f' | 'F' =>
-              !isIdentifierPart(lookahead.getc())
-
-            /** A little more special handling for e.g. 5e7 */
-            case 'e' | 'E' =>
-              val ch = lookahead.getc()
-              !isIdentifierPart(ch) || (isDigit(ch) || ch == '+' || ch == '-')
-
-            case x =>
-              !isIdentifierStart(x)
-          }
-        }
-        if (isDefinitelyNumber) {
-          putChar(ch)
-          nextChar()
-          getFraction()
+        val lookahead = lookaheadReader()
+        lookahead.nextChar()
+        if ('0' <= lookahead.ch && lookahead.ch <= '9') {
+          putChar('.'); nextChar(); getFraction()
         }
       } else (ch: @switch) match {
         case 'e' | 'E' | 'f' | 'F' | 'd' | 'D' =>

tests/neg/floatlits.scala

@@ -0,0 +1,11 @@
+object Test {
+
+  val y = .2 // ok
+
+  val z = 3.2 // ok
+
+  val a = 1.0e2
+  val b = 1e-3
+
+  val x = 2. // error: identifier expected
+}