cgen: fix fn call of sumtype with alias fntype variant (#16519)

vlib/v/gen/c/cgen.v

@@ -2281,7 +2281,6 @@ fn (mut g Gen) write_sumtype_casting_fn(fun SumtypeCastingFn) {
 	mut sb := strings.new_builder(128)
 	mut is_anon_fn := false
 	if got_sym.info is ast.FnType {
-		if got_sym.info.is_anon || g.table.known_fn(got_sym.name) {
 		got_name := 'fn ${g.table.fn_type_source_signature(got_sym.info.func)}'
 		got_cname = 'anon_fn_${g.table.fn_type_signature(got_sym.info.func)}'
 		type_idx = g.table.type_idxs[got_name].str()
@@ -2300,7 +2299,6 @@ fn (mut g Gen) write_sumtype_casting_fn(fun SumtypeCastingFn) {
 		sb.writeln('\t${got_cname} ptr = x;')
 		is_anon_fn = true
 	}
-	}
 	if !is_anon_fn {
 		sb.writeln('static inline ${exp_cname} ${fun.fn_name}(${got_cname}* x) {')
 		sb.writeln('\t${got_cname}* ptr = memdup(x, sizeof(${got_cname}));')
@@ -2436,8 +2434,8 @@ fn (mut g Gen) expr_with_cast(expr ast.Expr, got_type_raw ast.Type, expected_typ
 	if got_sym.info is ast.FnType {
 		if got_sym.info.is_anon {
 			got_styp = 'anon_fn_${g.table.fn_type_signature(got_sym.info.func)}'
-			got_is_fn = true
 		}
+		got_is_fn = true
 	}
 	if expected_type != ast.void_type {
 		unwrapped_expected_type := g.unwrap_generic(expected_type)

vlib/v/gen/c/fn.v

@@ -1452,8 +1452,9 @@ fn (mut g Gen) fn_call(node ast.CallExpr) {
 							}
 						}
 						if obj.smartcasts.len > 0 && is_cast_needed {
-							for _ in obj.smartcasts {
-								g.write('(*')
+							for typ in obj.smartcasts {
+								sym := g.table.sym(typ)
+								g.write('(*(${sym.cname})(')
 							}
 							for i, typ in obj.smartcasts {
 								cast_sym := g.table.sym(g.unwrap_generic(typ))
@@ -1471,7 +1472,7 @@ fn (mut g Gen) fn_call(node ast.CallExpr) {
 								} else {
 									g.write('${dot}_${cast_sym.cname}')
 								}
-								g.write(')')
+								g.write('))')
 							}
 							is_fn_var = true
 						} else if obj.is_inherited {

vlib/v/tests/sumtype_with_alias_fntype_test.v

@@ -11,18 +11,25 @@ fn abc(i int) int {
 	return i
 }
 
+// create Myfn
+fn myfnfact() Myfn {
+	return abc
+}
+
+// run fn if exists
 fn run(mmff Maybefnfact) string {
 	match mmff {
-		Myfnfact { return 'yes fn' }
-		None { return 'None fn' }
+		Myfnfact {
+			r := mmff()
+			return 'yes fn: ${r}'
+		}
+		None {
+			return 'None fn'
+		}
 	}
 }
 
 fn test_sumtype_with_alias_fntype() {
-	// create Myfn
-	myfnfact := fn () Myfn {
-		return abc
-	}
 	r1 := main.myfnfact()(1)
 	println(r1)
 	assert r1 == 1
@@ -33,5 +40,5 @@ fn test_sumtype_with_alias_fntype() {
 
 	r3 := run(myfnfact)
 	println(r3)
-	assert r3 == 'yes fn'
+	assert r3 == 'yes fn: fn (int) int'
 }