add changelog entry, fix double not nil bug

changelog.md

@@ -142,6 +142,11 @@
   need to convert to `string`. On the JS backend, this is translated directly
   to a `switch` statement.
 
+- `foo a = b` now means `foo(a = b)` rather than `foo(a) = b`. This is consistent
+  with the existing behavior of `foo a, b = c` meaning `foo(a, b = c)`.
+  This decision was made with the assumption that the old syntax was used rarely;
+  if your code used the old syntax, please be aware of this change.
+
 ## Compiler changes
 
 - The `gc` switch has been renamed to `mm` ("memory management") in order to reflect the

compiler/parser.nim

@@ -1393,9 +1393,7 @@ proc parseTypeDefValue(p: var Parser): PNode =
     result = parseTypeClass(p)
   else:
     result = simpleExpr(p, pmTypeDef)
-    if p.tok.tokType == tkNot:
-      result = binaryNot(p, result)
-    else:
+    if p.tok.tokType != tkNot:
       if result.kind == nkCommand:
         var isFirstParam = false
         while p.tok.tokType == tkComma:

tests/parser/tdoublenotnil.nim

@@ -0,0 +1,3 @@
+when false:
+  type Foo = Bar not nil not nil #[tt.Error
+                         ^ invalid indentation]#