typing: new warning useless-null-test that detect == and != between non-nullables...

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/src/semantize/typing.nit b/src/semantize/typing.nit
index f254292..c581f47 100644 (file)
--- a/src/semantize/typing.nit
+++ b/src/semantize/typing.nit
@@ -206,7 +206,11 @@ private class TypeVisitor
 
                if not mtype2 isa MNullType then return
 
+               # Check of useless null
                if not mtype isa MNullableType then
+                       if not anchor_to(mtype) isa MNullableType then
+                               modelbuilder.warning(anode, "useless-null-test", "Warning: expression is not null, since it is a `{mtype}`.")
+                       end
                        return
                end