fixes discard no return type proc (#1206)

ref #1201

We need to inspect the type of its parameter instead of the type of
`discard`

Author: ringabout

src/nimony/renderer.nim

@@ -981,6 +981,9 @@ proc gtype(g: var SrcGen, n: var Cursor, c: Context) =
         gsub(g, n, c)
       else:
         skip n
+  of DotToken:
+    put(g, tkSymbol, "void")
+    inc n
   else:
     gsub(g, n, c)
 

src/nimony/sem.nim

@@ -1930,8 +1930,8 @@ proc semDiscard(c: var SemContext; it: var Item) =
     var a = Item(n: it.n, typ: c.types.autoType)
     semExpr c, a
     it.n = a.n
-    if classifyType(c, it.typ) == VoidT:
-      buildErr c, exInfo, "expression of type `" & typeToString(it.typ) & "` must not be discarded"
+    if classifyType(c, a.typ) == VoidT:
+      buildErr c, exInfo, "expression of type `" & typeToString(a.typ) & "` must not be discarded"
   takeParRi c, it.n
   producesVoid c, info, it.typ
 

tests/nimony/sysbasics/tdiscardvoidcalls.msgs

@@ -0,0 +1 @@
+tests/nimony/sysbasics/tdiscardvoidcalls.nim(4, 12) Error: expression of type `void` must not be discarded

tests/nimony/sysbasics/tdiscardvoidcalls.nim

@@ -0,0 +1,4 @@
+proc foo =
+  discard
+
+discard foo()