From 8f48533691e93538846993f78f732272a03a600b Mon Sep 17 00:00:00 2001
From: Travis Staloch <1562827+travisstaloch@users.noreply.github.com>
Date: Thu, 26 Oct 2023 21:12:47 -0700
Subject: [PATCH] GenericReader error set fixes

add error.EndOfStream to readEnum() and isBytes() so that users can
catch these errors.  this also prevents them from panicing with
'invalid error value' on EndOfStream.

test both methods.
---
 lib/std/io.zig      |  4 ++--
 lib/std/io/test.zig | 13 +++++++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/lib/std/io.zig b/lib/std/io.zig
index 64ed9f757e..8bbc8d6150 100644
--- a/lib/std/io.zig
+++ b/lib/std/io.zig
@@ -308,7 +308,7 @@ pub fn GenericReader(
             return @errorCast(self.any().skipBytes(num_bytes, options));
         }
 
-        pub inline fn isBytes(self: Self, slice: []const u8) Error!bool {
+        pub inline fn isBytes(self: Self, slice: []const u8) NoEofError!bool {
             return @errorCast(self.any().isBytes(slice));
         }
 
@@ -320,7 +320,7 @@ pub fn GenericReader(
             return @errorCast(self.any().readStructBig(T));
         }
 
-        pub const ReadEnumError = Error || error{
+        pub const ReadEnumError = NoEofError || error{
             /// An integer was read, but it did not match any of the tags in the supplied enum.
             InvalidValue,
         };
diff --git a/lib/std/io/test.zig b/lib/std/io/test.zig
index 46c40512e2..3967469e6f 100644
--- a/lib/std/io/test.zig
+++ b/lib/std/io/test.zig
@@ -182,3 +182,16 @@ test "updateTimes" {
     try expect(stat_new.atime < stat_old.atime);
     try expect(stat_new.mtime < stat_old.mtime);
 }
+
+test "GenericReader methods can return error.EndOfStream" {
+    // https://github.com/ziglang/zig/issues/17733
+    var fbs = std.io.fixedBufferStream("");
+    try std.testing.expectError(
+        error.EndOfStream,
+        fbs.reader().readEnum(enum(u8) { a, b }, .Little),
+    );
+    try std.testing.expectError(
+        error.EndOfStream,
+        fbs.reader().isBytes("foo"),
+    );
+}