Add parsing and cppfront emit lambdas in alternatives

Author: filipsajdak

source/cppfront.cpp

@@ -1283,10 +1283,16 @@ class cppfront
             auto id = std::string{};
             printer.emit_to_string(&id);
             assert(alt->id_expression || alt->literal);
-            if (alt->id_expression)
+            if (alt->id_expression) {
                 emit(*alt->id_expression);
-            else if (alt->literal)
+                if (alt->expr) {
+                    push_need_expression_list_parens(true);
+                    emit(*alt->expr);
+                    pop_need_expression_list_parens();
+                }
+            } else if (alt->literal) {
                 emit(*alt->literal);
+            }
             printer.emit_to_string();
 
             assert (*alt->is_as_keyword == "is" || *alt->is_as_keyword == "as");

source/parse.h

@@ -668,6 +668,7 @@ struct alternative_node
     source_position                      equal_sign;
     std::unique_ptr<statement_node>      statement;
     token const*                         literal;
+    std::unique_ptr<expression_list_node> expr;
 
     auto position() const -> source_position
     {
@@ -2359,6 +2360,25 @@ class parser
             return {};
         }
 
+        if (curr().type() == lexeme::LeftParen) {
+            auto open_paren = curr().position();
+            next();
+            auto expr_list = expression_list(open_paren);
+            if (!expr_list) {
+                error("unexpected text - ( is not followed by an expression-list");
+                next();
+                return {};
+            }
+            if (curr().type() != lexeme::RightParen) {
+                error("unexpected text - expression-list is not terminated by )");
+                next();
+                return {};
+            }
+            expr_list->close_paren = curr().position();
+            next();
+            n->expr = std::move(expr_list);
+        }
+
         if (curr().type() != lexeme::Assignment) {
             error("expected = at start of inspect alternative body");
             return {};