Fix error position and msg for expression expected

Author: odersky

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

@@ -275,13 +275,13 @@ object Parsers {
     /** If at end of file, issue an incompleteInputError.
      *  Otherwise issue a syntax error and skip to next safe point.
      */
-    def syntaxErrorOrIncomplete(msg: => Message): Unit =
+    def syntaxErrorOrIncomplete(msg: => Message, offset: Int = in.offset): Unit =
       if (in.token == EOF) incompleteInputError(msg)
       else {
-        syntaxError(msg)
+        syntaxError(msg, offset)
         skip()
         lastErrorOffset = in.offset
-      } // DEBUG
+      }
 
     /** Consume one token of the specified type, or
       * signal an error if it is not there.
@@ -1456,7 +1456,7 @@ object Parsers {
         case _ =>
           if (isLiteral) literal()
           else {
-            syntaxErrorOrIncomplete(IllegalStartSimpleExpr(tokenString(in.token)))
+            syntaxErrorOrIncomplete(IllegalStartSimpleExpr(tokenString(in.token)), in.lastOffset)
             errorTermTree
           }
       }

compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala

@@ -569,19 +569,9 @@ object messages {
   case class IllegalStartSimpleExpr(illegalToken: String)(implicit ctx: Context)
   extends Message(IllegalStartSimpleExprID) {
     val kind: String = "Syntax"
-    val msg: String = "Illegal start of simple expression"
+    val msg: String = "expression expected"
     val explanation: String = {
-      hl"""|An expression yields a value. In the case of the simple expression, this error
-           |commonly occurs when there's a missing parenthesis or brace. The reason being
-           |that a simple expression is one of the following:
-           |
-           |- Block
-           |- Expression in parenthesis
-           |- Identifier
-           |- Object creation
-           |- Literal
-           |
-           |which cannot start with ${Red(illegalToken)}."""
+      hl"""|An expression cannot start with ${Red(illegalToken)}."""
     }
   }
 

tests/neg/errpos.scala

@@ -0,0 +1,4 @@
+object Test {
+  val x =     // error: expression expected
+  val y = 2   // error: ';' expected
+}