Properly wrap discarded statements (#10322)

Failing to do so lead the codegen to emit invalid code sometimes,
especially when C++ references were involved.

Fixes #10241

compiler/semexprs.nim

@@ -917,7 +917,7 @@ proc semExprNoType(c: PContext, n: PNode): PNode =
   let isPush = hintExtendedContext in c.config.notes
   if isPush: pushInfoContext(c.config, n.info)
   result = semExpr(c, n, {efWantStmt})
-  discardCheck(c, result, {})
+  result = discardCheck(c, result, {})
   if isPush: popInfoContext(c.config)
 
 proc isTypeExpr(n: PNode): bool =
@@ -1639,7 +1639,7 @@ proc semProcBody(c: PContext, n: PNode): PNode =
       a.sons[1] = result
       result = semAsgn(c, a)
   else:
-    discardCheck(c, result, {})
+    result = discardCheck(c, result, {})
 
   if c.p.owner.kind notin {skMacro, skTemplate} and
      c.p.resultSym != nil and c.p.resultSym.typ.isMetaType: