From 7749ffd797e927f93051060db49b76c595879697 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Sun, 5 Feb 2017 18:58:58 -0500
Subject: [PATCH] try expression can omit variable assignments

---
 doc/langref.md     |  2 +-
 src/parser.cpp     | 27 ++++++++++++++++-----------
 test/cases/try.zig | 26 ++++++++++++++++++++++++++
 3 files changed, 43 insertions(+), 12 deletions(-)

diff --git a/doc/langref.md b/doc/langref.md
index f3eb6b99f6..b8a6a5775a 100644
--- a/doc/langref.md
+++ b/doc/langref.md
@@ -93,7 +93,7 @@ IfExpression = IfVarExpression | IfBoolExpression
 
 IfBoolExpression = "if" "(" Expression ")" Expression option(Else)
 
-TryExpression = "try" "(" ("const" | "var") option("*") Symbol "=" Expression  ")" Expression option("else" option("|" Symbol "|") Expression)
+TryExpression = "try" "(" option(("const" | "var") option("*") Symbol "=") Expression  ")" Expression option("else" option("|" Symbol "|") Expression)
 
 IfVarExpression = "if" "(" ("const" | "var") option("*") Symbol option(":" TypeExpr) "?=" Expression ")" Expression Option(Else)
 
diff --git a/src/parser.cpp b/src/parser.cpp
index 68ccd6aff4..57b226270a 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -628,7 +628,7 @@ static AstNode *ast_parse_comptime_expr(ParseContext *pc, size_t *token_index, b
 }
 
 /*
-TryExpression = "try" "(" ("const" | "var") option("*") Symbol "=" Expression  ")" Expression option("else" option("|" Symbol "|") Expression)
+TryExpression = "try" "(" option(("const" | "var") option("*") Symbol "=") Expression  ")" Expression option("else" option("|" Symbol "|") Expression)
 */
 static AstNode *ast_parse_try_expr(ParseContext *pc, size_t *token_index, bool mandatory) {
     Token *try_token = &pc->tokens->at(*token_index);
@@ -646,27 +646,32 @@ static AstNode *ast_parse_try_expr(ParseContext *pc, size_t *token_index, bool m
     ast_eat_token(pc, token_index, TokenIdLParen);
 
     Token *var_token = &pc->tokens->at(*token_index);
+    bool have_vars;
     if (var_token->id == TokenIdKeywordVar) {
         node->data.try_expr.var_is_const = false;
         *token_index += 1;
+        have_vars = true;
     } else if (var_token->id == TokenIdKeywordConst) {
         node->data.try_expr.var_is_const = true;
         *token_index += 1;
+        have_vars = true;
     } else {
-        ast_invalid_token_error(pc, var_token);
+        have_vars = false;
     }
 
-    Token *star_token = &pc->tokens->at(*token_index);
-    if (star_token->id == TokenIdStar) {
-        node->data.try_expr.var_is_ptr = true;
-        *token_index += 1;
+    if (have_vars) {
+        Token *star_token = &pc->tokens->at(*token_index);
+        if (star_token->id == TokenIdStar) {
+            node->data.try_expr.var_is_ptr = true;
+            *token_index += 1;
+        }
+
+        Token *var_name_tok = ast_eat_token(pc, token_index, TokenIdSymbol);
+        node->data.try_expr.var_symbol = token_buf(var_name_tok);
+
+        ast_eat_token(pc, token_index, TokenIdEq);
     }
 
-    Token *var_name_tok = ast_eat_token(pc, token_index, TokenIdSymbol);
-    node->data.try_expr.var_symbol = token_buf(var_name_tok);
-
-    ast_eat_token(pc, token_index, TokenIdEq);
-
     node->data.try_expr.target_node = ast_parse_expression(pc, token_index, true);
 
     ast_eat_token(pc, token_index, TokenIdRParen);
diff --git a/test/cases/try.zig b/test/cases/try.zig
index 17b78b2115..cf1bf49157 100644
--- a/test/cases/try.zig
+++ b/test/cases/try.zig
@@ -31,3 +31,29 @@ error CrappedOut;
 fn returnsTen() -> %i32 {
     10
 }
+
+fn tryWithoutVars() {
+    @setFnTest(this);
+
+    const result1 = try (failIfTrue(true)) {
+        1
+    } else {
+        i32(2)
+    };
+    assert(result1 == 2);
+
+    const result2 = try (failIfTrue(false)) {
+        1
+    } else {
+        i32(2)
+    };
+    assert(result2 == 1);
+}
+
+fn failIfTrue(ok: bool) -> %void {
+    if (ok) {
+        return error.ItBroke;
+    } else {
+        return;
+    }
+}