cgen: fix anon_fn in containers (fix #8965) (#9049)

vlib/v/gen/c/cgen.v

@@ -1952,7 +1952,18 @@ fn (mut g Gen) gen_assign_stmt(assign_stmt ast.AssignStmt) {
 					g.definitions.go_back(g.definitions.len - def_pos)
 					g.write(') = ')
 				} else {
+					g.is_assign_lhs = true
+					g.assign_op = assign_stmt.op
 					g.expr(left)
+					g.is_assign_lhs = false
+					if left is ast.IndexExpr {
+						sym := g.table.get_type_symbol(left.left_type)
+						if sym.kind in [.map, .array] {
+							g.expr(val)
+							g.writeln('});')
+							continue
+						}
+					}
 					g.write(' = ')
 				}
 				g.expr(val)

vlib/v/tests/anon_fn_in_containers_test.v

@@ -0,0 +1,13 @@
+fn test_anon_fn_in_map() {
+	mut woop := map{
+		'what': fn() string {
+			return 'whoopity whoop'
+		}
+	}
+	assert woop['what']() == 'whoopity whoop'
+
+	woop['shat'] = fn() string {
+		return 'shoopity shoop'
+	}
+	assert woop['shat']() == 'shoopity shoop'
+}