all: implement multiple generics (#8231)

vlib/v/ast/ast.v

@@ -324,7 +324,7 @@ pub:
 	pos             token.Position // function declaration position
 	body_pos        token.Position // function bodys position
 	file            string
-	is_generic      bool
+	generic_params  []GenericParam
 	is_direct_arr   bool // direct array access
 	attrs           []table.Attr
 pub mut:
@@ -336,6 +336,11 @@ pub mut:
 	scope         &Scope
 }
 
+pub struct GenericParam {
+pub:
+	name string
+}
+
 // break, continue
 pub struct BranchStmt {
 pub:
@@ -362,7 +367,7 @@ pub mut:
 	receiver_type      table.Type // User
 	return_type        table.Type
 	should_be_skipped  bool
-	generic_type       table.Type // TODO array, to support multiple types
+	generic_types      []table.Type
 	generic_list_pos   token.Position
 	free_receiver      bool // true if the receiver expression needs to be freed
 	scope              &Scope

vlib/v/ast/str.v

@@ -59,8 +59,16 @@ pub fn (node &FnDecl) stringify(t &table.Table, cur_mod string, m2a map[string]s
 	if name in ['+', '-', '*', '/', '%', '<', '>', '==', '!=', '>=', '<='] {
 		f.write(' ')
 	}
-	if node.is_generic {
-		f.write('<T>')
+	if node.generic_params.len > 0 {
+		f.write('<')
+		for i, param in node.generic_params {
+			is_last := i == node.generic_params.len - 1
+			f.write(param.name)
+			if !is_last {
+				f.write(', ')
+			}
+		}
+		f.write('>')
 	}
 	f.write('(')
 	for i, arg in node.params {