Fix #10268: Stop scanning operator before parsing comment

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

@@ -960,8 +960,9 @@ object Scanners {
            '|' | '\\' =>
         putChar(ch); nextChar(); getOperatorRest()
       case '/' =>
-        if (skipComment()) finishNamed()
-        else { putChar('/'); getOperatorRest() }
+        val nxch = lookaheadChar()
+        if nxch == '/' || nxch == '*' then finishNamed()
+        else { putChar(ch); nextChar(); getOperatorRest() }
       case _ =>
         if (isSpecial(ch)) { putChar(ch); nextChar(); getOperatorRest() }
         else finishNamed()

tests/neg/i10268.check

@@ -0,0 +1,6 @@
+-- [E006] Not Found Error: tests/neg/i10268.scala:2:16 -----------------------------------------------------------------
+2 |  def test[T] = ?//test // error
+  |                ^
+  |                Not found: ?
+
+longer explanation available when compiling with `-explain`

tests/neg/i10268.scala

@@ -0,0 +1,3 @@
+object Main {
+  def test[T] = ?//test // error
+}

tests/neg/multiLineOps.scala

@@ -5,7 +5,7 @@ val x = 1
 val b1 = {
   22
   * 22  // ok
-  */*one more*/22 // error: end of statement expected
+  */*one more*/22 // error: end of statement expected // error: not found: *
 }                 // error: ';' expected, but '}' found
 
 val b2: Boolean = {