Infix warn on migration

src/compiler/scala/tools/nsc/ast/parser/Scanners.scala

@@ -13,6 +13,7 @@
 package scala.tools.nsc
 package ast.parser
 
+import scala.tools.nsc.settings.ScalaVersion
 import scala.tools.nsc.util.{CharArrayReader, CharArrayReaderData}
 import scala.reflect.internal.util._
 import scala.reflect.internal.Chars._
@@ -403,6 +404,9 @@ trait Scanners extends ScannersCommon {
       sepRegions = sepRegions.tail
     }
 
+    /** True to warn about migration change in infix syntax. */
+    private val infixMigration = settings.Xmigration.value <= ScalaVersion("2.13.2")
+
     /** Produce next token, filling TokenData fields of Scanner.
      */
     def nextToken(): Unit = {
@@ -487,7 +491,7 @@ trait Scanners extends ScannersCommon {
                        |will be taken as an infix expression continued from the previous line.
                        |To force the previous interpretation as a separate statement,
                        |add an explicit `;`, add an empty line, or remove spaces after the operator."""
-          deprecationWarning(msg.stripMargin, "2.13.2")
+          if (infixMigration) deprecationWarning(msg.stripMargin, "2.13.2")
           insertNL(NEWLINE)
         }
       }

test/files/neg/multiLineOps.check

@@ -1,5 +1,5 @@
 multiLineOps.scala:6: warning: a pure expression does nothing in statement position; multiline expressions may require enclosing parentheses
-    +3 // error: Expected a toplevel definition (or pure expr warning, here)
+    +3 // warning: a pure expression does nothing in statement position
     ^
 error: No warnings can be incurred under -Werror.
 1 warning

test/files/neg/multiLineOps.scala

@@ -3,5 +3,5 @@
 class Test {
   val x = 1
     + 2
-    +3 // error: Expected a toplevel definition (or pure expr warning, here)
+    +3 // warning: a pure expression does nothing in statement position
 }

test/files/neg/stmt-expr-discard.check

@@ -1,21 +1,9 @@
-stmt-expr-discard.scala:5: warning: Line starts with an operator that in future
-will be taken as an infix expression continued from the previous line.
-To force the previous interpretation as a separate statement,
-add an explicit `;`, add an empty line, or remove spaces after the operator.
-    + 2
-    ^
-stmt-expr-discard.scala:6: warning: Line starts with an operator that in future
-will be taken as an infix expression continued from the previous line.
-To force the previous interpretation as a separate statement,
-add an explicit `;`, add an empty line, or remove spaces after the operator.
-    - 4
-    ^
 stmt-expr-discard.scala:5: warning: a pure expression does nothing in statement position; multiline expressions may require enclosing parentheses
     + 2
     ^
 stmt-expr-discard.scala:6: warning: a pure expression does nothing in statement position; multiline expressions may require enclosing parentheses
     - 4
     ^
 error: No warnings can be incurred under -Werror.
-4 warnings
+2 warnings
 1 error

test/files/neg/t12071.scala

@@ -1,4 +1,4 @@
-// scalac: -Werror -Xlint
+// scalac: -Werror -Xlint -Xmigration:2.13
 
 class C {
   def `c c`(n: Int): Int = n + 1

test/files/neg/t9847.check

@@ -1,15 +1,3 @@
-t9847.scala:10: warning: Line starts with an operator that in future
-will be taken as an infix expression continued from the previous line.
-To force the previous interpretation as a separate statement,
-add an explicit `;`, add an empty line, or remove spaces after the operator.
-  + 1
-  ^
-t9847.scala:14: warning: Line starts with an operator that in future
-will be taken as an infix expression continued from the previous line.
-To force the previous interpretation as a separate statement,
-add an explicit `;`, add an empty line, or remove spaces after the operator.
-  + 1
-  ^
 t9847.scala:6: warning: discarded non-Unit value
   def f(): Unit = 42
                   ^
@@ -47,5 +35,5 @@ t9847.scala:24: warning: a pure expression does nothing in statement position; m
   class D { 42 ; 17 }
                  ^
 error: No warnings can be incurred under -Werror.
-14 warnings
+12 warnings
 1 error