[Cpp] Fixes an issue when mixing hooks and calls (#23428)

compiler/ccgstmts.nim

@@ -369,7 +369,10 @@ proc genSingleVar(p: BProc, v: PSym; vn, value: PNode) =
         line(p, cpsStmts, decl)
       else:
         tmp = initLocExprSingleUse(p, value)
-        lineF(p, cpsStmts, "$# = $#;\n", [decl, tmp.rdLoc])
+        if value.kind == nkEmpty:
+          lineF(p, cpsStmts, "$#;\n", [decl])
+        else:
+          lineF(p, cpsStmts, "$# = $#;\n", [decl, tmp.rdLoc])
       return
     assignLocalVar(p, vn)
     initLocalVar(p, v, imm)

compiler/cgen.nim

@@ -1208,6 +1208,7 @@ proc genProcAux*(m: BModule, prc: PSym) =
     elif sfConstructor in prc.flags:
       resNode.sym.loc.flags.incl lfIndirect
       fillLoc(resNode.sym.loc, locParam, resNode, "this", OnHeap)
+      prc.loc.r = getTypeDesc(m, resNode.sym.loc.t, dkVar)
     else:
       fillResult(p.config, resNode, prc.typ)
       assignParam(p, res, prc.typ.returnType)

tests/cpp/tconstructor.nim

@@ -115,4 +115,17 @@ type Foo {.exportc.} = object
 
 proc makeFoo(): Foo {.used, constructor, nodecl.} = discard
 
-echo $Foo()
+echo $Foo()
+
+type Boo = object
+proc `=copy`(dest: var Boo; src: Boo) = discard
+
+proc makeBoo(): Boo {.constructor.} = Boo()
+proc makeBoo2(): Boo  = Boo()
+
+block:
+  proc main =
+    var b = makeBoo()
+    var b2 = makeBoo2()
+
+  main()