From 5cbe930e36d9ccd6ac90d15a2354aced5d54f0dc Mon Sep 17 00:00:00 2001
From: Luuk de Gram <Luukdegram@users.noreply.github.com>
Date: Fri, 28 May 2021 11:52:08 +0200
Subject: [PATCH] wasm: Add stage2 tests for error unions

---
 src/codegen/wasm.zig |  6 +++--
 test/stage2/wasm.zig | 64 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/src/codegen/wasm.zig b/src/codegen/wasm.zig
index f2e318b9c5..528b233589 100644
--- a/src/codegen/wasm.zig
+++ b/src/codegen/wasm.zig
@@ -692,13 +692,15 @@ pub const Context = struct {
             .Struct => return self.fail(.{ .node_offset = 0 }, "TODO: Implement struct as return type for wasm", .{}),
             .Optional => return self.fail(.{ .node_offset = 0 }, "TODO: Implement optionals as return type for wasm", .{}),
             .ErrorUnion => {
-                try leb.writeULEB128(writer, @as(u32, 2));
                 const val_type = try self.genValtype(
                     .{ .node_offset = 0 },
                     return_type.errorUnionChild(),
                 );
-                try writer.writeByte(val_type);
+
+                // write down the amount of return values
+                try leb.writeULEB128(writer, @as(u32, 2));
                 try writer.writeByte(wasm.valtype(.i32)); // error code is always an i32 integer.
+                try writer.writeByte(val_type);
             },
             else => |ret_type| {
                 try leb.writeULEB128(writer, @as(u32, 1));
diff --git a/test/stage2/wasm.zig b/test/stage2/wasm.zig
index e62fcd3bac..828292d2a4 100644
--- a/test/stage2/wasm.zig
+++ b/test/stage2/wasm.zig
@@ -535,4 +535,68 @@ pub fn addCases(ctx: *TestContext) !void {
             \\}
         , "2\n");
     }
+
+    {
+        var case = ctx.exe("wasm error unions", wasi);
+
+        case.addCompareOutput(
+            \\pub export fn _start() void {
+            \\    var e1 = error.Foo;
+            \\    var e2 = error.Bar;
+            \\    assert(e1 != e2);
+            \\    assert(e1 == error.Foo);
+            \\    assert(e2 == error.Bar);
+            \\}
+            \\
+            \\fn assert(b: bool) void {
+            \\    if (!b) unreachable;
+            \\}
+        , "");
+
+        case.addCompareOutput(
+            \\pub export fn _start() u32 {
+            \\    var e: anyerror!u32 = 5;
+            \\    const i = e catch 10;
+            \\    return i;
+            \\}
+        , "5\n");
+
+        case.addCompareOutput(
+            \\pub export fn _start() u32 {
+            \\    var e: anyerror!u32 = error.Foo;
+            \\    const i = e catch 10;
+            \\    return i;
+            \\}
+        , "10\n");
+
+        case.addCompareOutput(
+            \\pub export fn _start() u32 {
+            \\    var e = foo();
+            \\    const i = e catch 69;
+            \\    return i;
+            \\}
+            \\
+            \\fn foo() anyerror!u32 {
+            \\    return 5;
+            \\}
+        , "5\n");
+    }
+
+    {
+        // TODO implement Type equality comparison of error unions in SEMA
+        // before we can incrementally compile functions with an error union as return type
+        var case = ctx.exe("wasm error union part 2", wasi);
+
+        case.addCompareOutput(
+            \\pub export fn _start() u32 {
+            \\    var e = foo();
+            \\    const i = e catch 69;
+            \\    return i;
+            \\}
+            \\
+            \\fn foo() anyerror!u32 {
+            \\    return error.Bruh;
+            \\}
+        , "69\n");
+    }
 }