cgen: fix anon_fn redefinition (#8961)

vlib/v/ast/ast.v

@@ -302,6 +302,7 @@ pub struct AnonFn {
 pub mut:
 	decl    FnDecl
 	typ     table.Type // the type of anonymous fn. Both .typ and .decl.name are auto generated
+	has_gen bool       // has been generated
 }
 
 // function or method declaration
@@ -361,7 +362,6 @@ pub:
 pub struct CallExpr {
 pub:
 	pos token.Position
-	left Expr // `user` in `user.register()`
 	mod string
 pub mut:
 	name               string // left.name()
@@ -371,6 +371,7 @@ pub mut:
 	expected_arg_types []table.Type
 	language           table.Language
 	or_block           OrExpr
+	left               Expr       // `user` in `user.register()`
 	left_type          table.Type // type of `user`
 	receiver_type      table.Type // User
 	return_type        table.Type

vlib/v/gen/c/array.v

@@ -150,11 +150,11 @@ fn (mut g Gen) gen_array_map(node ast.CallExpr) {
 	g.writeln('for (int $i = 0; $i < ${tmp}_len; ++$i) {')
 	g.writeln('\t$inp_elem_type it = (($inp_elem_type*) ${tmp}_orig.data)[$i];')
 	mut is_embed_map_filter := false
-	expr := node.args[0].expr
-	match expr {
+	mut expr := node.args[0].expr
+	match mut expr {
 		ast.AnonFn {
 			g.write('\t$ret_elem_type ti = ')
-			g.gen_anon_fn_decl(expr)
+			g.gen_anon_fn_decl(mut expr)
 			g.write('${expr.decl.name}(it)')
 		}
 		ast.Ident {
@@ -324,11 +324,11 @@ fn (mut g Gen) gen_array_filter(node ast.CallExpr) {
 	g.writeln('for (int $i = 0; $i < ${tmp}_len; ++$i) {')
 	g.writeln('\t$elem_type_str it = (($elem_type_str*) ${tmp}_orig.data)[$i];')
 	mut is_embed_map_filter := false
-	expr := node.args[0].expr
-	match expr {
+	mut expr := node.args[0].expr
+	match mut expr {
 		ast.AnonFn {
 			g.write('\tif (')
-			g.gen_anon_fn_decl(expr)
+			g.gen_anon_fn_decl(mut expr)
 			g.write('${expr.decl.name}(it)')
 		}
 		ast.Ident {

vlib/v/gen/c/cgen.v

@@ -2502,12 +2502,15 @@ fn (mut g Gen) autofree_var_call(free_fn_name string, v ast.Var) {
 	}
 }
 
-fn (mut g Gen) gen_anon_fn_decl(it ast.AnonFn) {
+fn (mut g Gen) gen_anon_fn_decl(mut node ast.AnonFn) {
+	if !node.has_gen {
 		pos := g.out.len
-	g.stmt(it.decl)
+		g.stmt(node.decl)
 		fn_body := g.out.after(pos)
 		g.out.go_back(fn_body.len)
 		g.anon_fn_definitions << fn_body
+		node.has_gen = true
+	}
 }
 
 fn (mut g Gen) map_fn_ptrs(key_typ table.TypeSymbol) (string, string, string, string) {
@@ -2560,10 +2563,10 @@ fn (mut g Gen) map_fn_ptrs(key_typ table.TypeSymbol) (string, string, string, st
 fn (mut g Gen) expr(node ast.Expr) {
 	// println('cgen expr() line_nr=$node.pos.line_nr')
 	// NB: please keep the type names in the match here in alphabetical order:
-	match node {
+	match mut node {
 		ast.AnonFn {
 			// TODO: dont fiddle with buffers
-			g.gen_anon_fn_decl(node)
+			g.gen_anon_fn_decl(mut node)
 			fsym := g.table.get_type_symbol(node.typ)
 			g.write(fsym.name)
 		}
@@ -5877,7 +5880,7 @@ fn (mut g Gen) go_expr(node ast.GoExpr) {
 fn (mut g Gen) go_stmt(node ast.GoStmt, joinable bool) string {
 	mut handle := ''
 	tmp := g.new_tmp_var()
-	expr := node.call_expr
+	mut expr := node.call_expr
 	mut name := expr.name // util.no_dots(expr.name)
 	// TODO: fn call is duplicated. merge with fn_call().
 	for i, generic_type in expr.generic_types {
@@ -5893,8 +5896,8 @@ fn (mut g Gen) go_stmt(node ast.GoStmt, joinable bool) string {
 	if expr.is_method {
 		receiver_sym := g.table.get_type_symbol(expr.receiver_type)
 		name = receiver_sym.name + '_' + name
-	} else if expr.left is ast.AnonFn {
-		g.gen_anon_fn_decl(expr.left)
+	} else if mut expr.left is ast.AnonFn {
+		g.gen_anon_fn_decl(mut expr.left)
 		fsym := g.table.get_type_symbol(expr.left.typ)
 		name = fsym.name
 	}

vlib/v/tests/anon_fn_redefinition_test.v

@@ -0,0 +1,24 @@
+const default_logger = Example{}
+
+struct Example {
+	structs []Another = [Another{}]
+}
+
+pub struct Another {
+	function fn (string) = fn (value string) {
+		println('$value')
+	}
+}
+
+pub fn (e Example) useless() string {
+	return 'ok'
+}
+
+fn test_anon_fn_redefinition() {
+	e1 := Example{}
+	assert e1.useless() == 'ok'
+	e2 := Example{}
+	assert e2.useless() == 'ok'
+	e3 := Example{}
+	assert e3.useless() == 'ok'
+}