Parse empty arguments in (invalid) Apply more often

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

@@ -249,11 +249,11 @@ object Parsers {
 
     /** Skip on error to next safe point.
      */
-    protected def skip(): Unit =
+    protected def skip(stopAtComma: Boolean): Unit =
       val lastRegion = in.currentRegion
       def atStop =
         in.token == EOF
-        || skipStopTokens.contains(in.token) && (in.currentRegion eq lastRegion)
+        || ((stopAtComma && in.token == COMMA) || skipStopTokens.contains(in.token)) && (in.currentRegion eq lastRegion)
       while !atStop do
         in.nextToken()
       lastErrorOffset = in.offset
@@ -278,7 +278,7 @@ object Parsers {
       if (in.token == EOF) incompleteInputError(msg)
       else
         syntaxError(msg, offset)
-        skip()
+        skip(stopAtComma = true)
 
     /** Consume one token of the specified type, or
       * signal an error if it is not there.
@@ -346,7 +346,7 @@ object Parsers {
             false // it's a statement that might be legal in an outer context
           else
             in.nextToken() // needed to ensure progress; otherwise we might cycle forever
-            skip()
+            skip(stopAtComma=false)
             true
 
       in.observeOutdented()
@@ -881,7 +881,8 @@ object Parsers {
       val next = in.lookahead.token
       next == LBRACKET || next == LPAREN
 
-    /** Is current ident a `*`, and is it followed by a `)` or `, )`? */
+    /** Is current ident a `*`, and is it followed by a `)`, `, )`, `,EOF`? The latter two are not
+        syntactically valid, but we need to include them here for error recovery. */
     def followingIsVararg(): Boolean =
       in.isIdent(nme.raw.STAR) && {
         val lookahead = in.LookaheadScanner()
@@ -890,7 +891,7 @@ object Parsers {
         || lookahead.token == COMMA
            && {
              lookahead.nextToken()
-             lookahead.token == RPAREN
+             lookahead.token == RPAREN || lookahead.token == EOF
            }
       }
 

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

@@ -659,8 +659,6 @@ object Scanners {
                  && (token == RPAREN || token == RBRACKET || token == RBRACE || token == OUTDENT)
               then
                 () /* skip the trailing comma */
-              else if token == EOF then // e.g. when the REPL is parsing "val List(x, y, _*,"
-                () /* skip the trailing comma */
               else
                 reset()
         case END =>

compiler/src/dotty/tools/repl/Main.scala

@@ -1,6 +1,7 @@
 package dotty.tools.repl
 
 /** Main entry point to the REPL */
+// To test, run bin/scala
 object Main {
   def main(args: Array[String]): Unit =
     new ReplDriver(args).tryRunning

tests/neg/arg-eof.scala

@@ -0,0 +1,3 @@
+object Test:
+  case class Widget(name: String, other: Int = 5)
+  Widget(name = "foo", // error // error

tests/neg/i1679.scala

@@ -1,5 +1,5 @@
 class A[T]
 object o {
   // Testing compiler crash, this test should be modified when named type argument are completely implemented
-  val x: A[T=Int, T=Int] = ??? // error: ']' expected, but '=' found
+  val x: A[T=Int, T=Int] = ??? // error: ']' expected, but '=' found // error
 }

tests/neg/t1625.check

@@ -0,0 +1,8 @@
+-- [E040] Syntax Error: tests/neg/t1625.scala:2:20 ---------------------------------------------------------------------
+2 |  def foo(x: String*, y: String*, c: String*): Int // error: an identifier expected, but ',' found // error: an identifier expected, but ',' found
+  |                    ^
+  |                    an identifier expected, but ',' found
+-- [E040] Syntax Error: tests/neg/t1625.scala:2:32 ---------------------------------------------------------------------
+2 |  def foo(x: String*, y: String*, c: String*): Int // error: an identifier expected, but ',' found // error: an identifier expected, but ',' found
+  |                                ^
+  |                                an identifier expected, but ',' found

tests/neg/t1625.scala

@@ -1,3 +1,3 @@
 trait T3 {
-  def foo(x: String*, y: String*, c: String*): Int // error: an identifier expected, but ',' found
-}
+  def foo(x: String*, y: String*, c: String*): Int // error: an identifier expected, but ',' found // error: an identifier expected, but ',' found
+}

tests/neg/t5702-neg-bad-and-wild.check

@@ -0,0 +1,44 @@
+-- [E032] Syntax Error: tests/neg/t5702-neg-bad-and-wild.scala:10:22 ---------------------------------------------------
+10 |      case List(1, _*,) => // error: pattern expected // error
+   |                      ^
+   |                      pattern expected
+   |
+   | longer explanation available when compiling with `-explain`
+-- [E032] Syntax Error: tests/neg/t5702-neg-bad-and-wild.scala:12:23 ---------------------------------------------------
+12 |      case List(1, _*3,) => // error: pattern expected // error // error
+   |                       ^
+   |                       pattern expected
+   |
+   | longer explanation available when compiling with `-explain`
+-- [E032] Syntax Error: tests/neg/t5702-neg-bad-and-wild.scala:15:18 ---------------------------------------------------
+15 |      case List(x*, 1) => // error: pattern expected
+   |                  ^
+   |                  pattern expected
+   |
+   | longer explanation available when compiling with `-explain`
+-- [E031] Syntax Error: tests/neg/t5702-neg-bad-and-wild.scala:17:18 ---------------------------------------------------
+17 |      case (1, x: _*) => // error: bad use of _* (sequence pattern not allowed)
+   |                  ^
+   |                  * can be used only for last argument
+   |
+   | longer explanation available when compiling with `-explain`
+-- [E032] Syntax Error: tests/neg/t5702-neg-bad-and-wild.scala:23:17 ---------------------------------------------------
+23 |    val K(ns @ _*, x) = k // error: pattern expected
+   |                 ^
+   |                 pattern expected
+   |
+   | longer explanation available when compiling with `-explain`
+-- Error: tests/neg/t5702-neg-bad-and-wild.scala:10:21 -----------------------------------------------------------------
+10 |      case List(1, _*,) => // error: pattern expected // error
+   |                     ^
+   |                     Values of types Null and Int cannot be compared with == or !=
+-- [E006] Not Found Error: tests/neg/t5702-neg-bad-and-wild.scala:12:20 ------------------------------------------------
+12 |      case List(1, _*3,) => // error: pattern expected // error // error
+   |                    ^
+   |                    Not found: *
+   |
+   | longer explanation available when compiling with `-explain`
+-- Error: tests/neg/t5702-neg-bad-and-wild.scala:12:22 -----------------------------------------------------------------
+12 |      case List(1, _*3,) => // error: pattern expected // error // error
+   |                      ^
+   |                      Values of types Null and Int cannot be compared with == or !=

tests/neg/t5702-neg-bad-brace.check

@@ -0,0 +1,10 @@
+-- [E032] Syntax Error: tests/neg/t5702-neg-bad-brace.scala:8:21 -------------------------------------------------------
+8 |      case List(1, _*} => // error: pattern expected
+  |                     ^
+  |                     pattern expected
+  |
+  | longer explanation available when compiling with `-explain`
+-- [E040] Syntax Error: tests/neg/t5702-neg-bad-brace.scala:11:0 -------------------------------------------------------
+11 |} // error: eof expected, but '}' found
+   |^
+   |eof expected, but '}' found

tests/neg/t5702-neg-bad-brace.scala

@@ -0,0 +1,11 @@
+
+object Test {
+
+  def main(args: Array[String]) = {
+    val is = List(1,2,3)
+
+    is match {
+      case List(1, _*} => // error: pattern expected
+    }
+  }
+} // error: eof expected, but '}' found

tests/neg/trailing-comma-pattern.check

@@ -0,0 +1,6 @@
+-- [E032] Syntax Error: tests/neg/trailing-comma-pattern.scala:3:8 -----------------------------------------------------
+3 |// error
+  |        ^
+  |        pattern expected
+  |
+  | longer explanation available when compiling with `-explain`

tests/neg/trailing-comma-pattern.scala

@@ -0,0 +1,3 @@
+object Test:
+  val List(x, y, _*,
+// error

tests/neg/trailing-comma-pattern2.check

@@ -0,0 +1,10 @@
+-- [E032] Syntax Error: tests/neg/trailing-comma-pattern2.scala:2:21 ---------------------------------------------------
+2 |  val List(x, y, _*, ) // error
+  |                     ^
+  |                     pattern expected
+  |
+  | longer explanation available when compiling with `-explain`
+-- [E040] Syntax Error: tests/neg/trailing-comma-pattern2.scala:3:8 ----------------------------------------------------
+3 |// error
+  |        ^
+  |        '=' expected, but unindent found

tests/neg/trailing-comma-pattern2.scala

@@ -0,0 +1,3 @@
+object Test:
+  val List(x, y, _*, ) // error
+// error

tests/pos/trailing-comma-pattern.scala

@@ -0,0 +1,3 @@
+object Test:
+  val List(x, y, _*,
+  ) = List(1, 2, 3)