From 5b7ae86af488745fc93cdbaff11bf2438938274a Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Sun, 21 Jan 2018 14:44:24 -0500
Subject: [PATCH] fix crash when switching on enum with 1 field and no switch
 prongs

closes #712
---
 src/ir.cpp              | 6 +++++-
 test/compile_errors.zig | 9 +++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/ir.cpp b/src/ir.cpp
index 77268327c8f89f6c546622e999d6925c366f7231..161e3397cc0aebeea47749fd1d001d105f45bbe5 100644
--- a/src/ir.cpp
+++ b/src/ir.cpp
@@ -4992,7 +4992,11 @@ static IrInstruction *ir_gen_switch_expr(IrBuilder *irb, Scope *scope, AstNode *
 
     ir_set_cursor_at_end_and_append_block(irb, end_block);
     assert(incoming_blocks.length == incoming_values.length);
-    return ir_build_phi(irb, scope, node, incoming_blocks.length, incoming_blocks.items, incoming_values.items);
+    if (incoming_blocks.length == 0) {
+        return ir_build_const_void(irb, scope, node);
+    } else {
+        return ir_build_phi(irb, scope, node, incoming_blocks.length, incoming_blocks.items, incoming_values.items);
+    }
 }
 
 static IrInstruction *ir_gen_comptime(IrBuilder *irb, Scope *parent_scope, AstNode *node, LVal lval) {
diff --git a/test/compile_errors.zig b/test/compile_errors.zig
index 22d1d65cc7e1d7875f4dde9fcd399f98a7663f25..d3c0c7cfeedc0ad204d2ba540d0a41c2bae01077 100644
--- a/test/compile_errors.zig
+++ b/test/compile_errors.zig
@@ -1,6 +1,15 @@
 const tests = @import("tests.zig");
 
 pub fn addCases(cases: &tests.CompileErrorContext) {
+    cases.add("switch on enum with 1 field with no prongs",
+        \\const Foo = enum { M };
+        \\
+        \\export fn entry() {
+        \\    var f = Foo.M;
+        \\    switch (f) {}
+        \\}
+    , ".tmp_source.zig:5:5: error: enumeration value 'Foo.M' not handled in switch");
+
     cases.add("shift by negative comptime integer",
         \\comptime {
         \\    var a = 1 >> -1;
-- 
2.54.0