ignore match errors to expected types of tuple constructor elements

fixes nim-lang#24609

compiler/semexprs.nim

@@ -2929,7 +2929,10 @@ proc semTupleFieldsConstr(c: PContext, n: PNode, flags: TExprFlags; expectedType
       # hasEmpty/nil check is to not break existing code like
       # `const foo = [(1, {}), (2, {false})]`,
       # `const foo = if true: (0, nil) else: (1, new(int))`
-      n[i][1] = fitNode(c, expectedElemType, n[i][1], n[i][1].info)
+      let conversion = indexTypesMatch(c, expectedElemType, n[i][1].typ, n[i][1])
+      # ignore matching error, full tuple will be matched later which may call converter, see #24609
+      if conversion != nil:
+        n[i][1] = conversion
 
     if n[i][1].typ.kind == tyTypeDesc:
       localError(c.config, n[i][1].info, "typedesc not allowed as tuple field.")

tests/tuples/ttupleconverter.nim

@@ -0,0 +1,18 @@
+# issue #24609
+
+import std/options
+
+type
+  Config* = object
+    bits*: tuple[r, g, b, a: Option[int32]]
+
+# works on 2.0.8
+#
+# results in error on 2.2.0
+#   type mismatch: got 'int literal(8)' for '8' but expected 'Option[system.int32]'
+#
+converter toInt32Tuple*(t: tuple[r,g,b,a: int]): tuple[r,g,b,a: Option[int32]] =
+  (some(t.r.int32), some(t.g.int32), some(t.b.int32), some(t.a.int32))
+
+var cfg: Config
+cfg.bits = (r: 8, g: 8, b: 8, a: 16)