SI-9847 Nuance pure expr statement warning

Clarify the current warning, which means that an expression
split over multiple lines may not be parsed as naively expected.

When typing a block, attempt minor nuance. For instance, a
single expression is not in need of parens. Try to avoid
duplicate warnings for expressions that were adapted away
from result position.

1 files changed, 9 insertions, 3 deletions

diff --git a/test/files/run/patmatnew.check b/test/files/run/patmatnew.check
index 56b8ac2f4f..117bc28c2d 100644
--- a/test/files/run/patmatnew.check
+++ b/test/files/run/patmatnew.check
@@ -1,10 +1,16 @@
-patmatnew.scala:351: warning: a pure expression does nothing in statement position; you may be omitting necessary parentheses
+patmatnew.scala:351: warning: a pure expression does nothing in statement position
         case 1 => "OK"
                   ^
-patmatnew.scala:352: warning: a pure expression does nothing in statement position; you may be omitting necessary parentheses
+patmatnew.scala:352: warning: a pure expression does nothing in statement position
         case 2 => assert(false); "KO"
                                  ^
-patmatnew.scala:353: warning: a pure expression does nothing in statement position; you may be omitting necessary parentheses
+patmatnew.scala:352: warning: multiline expressions might require enclosing parentheses; a value can be silently discarded when Unit is expected
+        case 2 => assert(false); "KO"
+                                 ^
+patmatnew.scala:353: warning: a pure expression does nothing in statement position
+        case 3 => assert(false); "KO"
+                                 ^
+patmatnew.scala:353: warning: multiline expressions might require enclosing parentheses; a value can be silently discarded when Unit is expected
         case 3 => assert(false); "KO"
                                  ^
 patmatnew.scala:670: warning: This catches all Throwables. If this is really intended, use `case e : Throwable` to clear this warning.