ast, parser, cgen: fix generic struct init (Stack[&Person]{}) (fix #19119) (#19122)

vlib/v/ast/table.v

@@ -1691,6 +1691,9 @@ pub fn (mut t Table) resolve_generic_to_concrete(generic_type Type, generic_name
 						t_generic_names, t_concrete_types)
 					{
 						gts := t.sym(ct)
+						if ct.is_ptr() {
+							nrt += '&'
+						}
 						nrt += gts.name
 						rnrt += gts.name
 						if i != sym.info.generic_types.len - 1 {
@@ -1867,6 +1870,9 @@ pub fn (mut t Table) unwrap_generic_type(typ Type, generic_names []string, concr
 					t_concrete_types)
 				{
 					gts := t.sym(ct)
+					if ct.is_ptr() {
+						nrt += '&'
+					}
 					nrt += gts.name
 					c_nrt += gts.cname
 					if i != ts.info.generic_types.len - 1 {

vlib/v/gen/c/if.v

@@ -184,20 +184,22 @@ fn (mut g Gen) if_expr(node ast.IfExpr) {
 	mut cur_line := ''
 	mut raw_state := false
 	if needs_tmp_var {
+		mut styp := g.typ(node.typ)
 		if node.typ.has_flag(.option) {
 			raw_state = g.inside_if_option
 			defer {
 				g.inside_if_option = raw_state
 			}
 			g.inside_if_option = true
+			styp = styp.replace('*', '_ptr')
 		} else if node.typ.has_flag(.result) {
 			raw_state = g.inside_if_result
 			defer {
 				g.inside_if_result = raw_state
 			}
 			g.inside_if_result = true
+			styp = styp.replace('*', '_ptr')
 		}
-		styp := g.typ(node.typ)
 		cur_line = g.go_before_stmt(0)
 		g.empty_line = true
 		g.writeln('${styp} ${tmp}; /* if prepend */')

vlib/v/parser/parse_type.v

@@ -763,6 +763,9 @@ fn (mut p Parser) parse_generic_inst_type(name string) ast.Type {
 		if gts.kind == .multi_return {
 			p.error_with_pos('cannot use multi return as generic concrete type', type_pos)
 		}
+		if gt.is_ptr() {
+			bs_name += '&'
+		}
 		bs_name += gts.name
 		bs_cname += gts.cname
 		concrete_types << gt

vlib/v/tests/generic_struct_init_with_reference_struct_type_test.v

@@ -0,0 +1,22 @@
+import datatypes { Stack }
+
+struct Person {
+mut:
+	name string
+	age  int
+}
+
+fn test_generic_struct_init_with_reference_struct_type() {
+	mut adam := &Person{'Adam', 21}
+	println(adam)
+
+	mut people := Stack[&Person]{}
+	people.push(adam)
+	assert people.len() == 1
+
+	mut top_person := people.pop()!
+	top_person.age++
+	println(adam)
+
+	assert people.len() == 0
+}