Irrelevant code suggestions after . (dot)

[nns2009]

Create slice "cs", for example:

cell actions;
slice cs = actions.begin_parse();

Type cs.l (small L) then Ctrl+Space, suggestions show up, but

Current behavior: they include irrelevant suggestions = such that the first parameter of the function is not "slice" Expected behavior: only relevant suggestions (with first parameter of type "slice") show up

[andreypfau]

Requires #118