Commit eb4024036d3e8e0c4a8b0dcf09da107421f3fa01 | zig

2 files changed, 20 insertions(+), 0 deletions(-)

src/Sema.zig+5

 @@ -4221,6 +4221,11 @@ fn zirForLen(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Air.
                     const msg = try sema.errMsg(block, arg_src, "type '{}' is not indexable and not a range", .{object_ty.fmt(sema.mod)});
                     errdefer msg.destroy(sema.gpa);
                     try sema.errNote(block, arg_src, msg, "for loop operand must be a range, array, slice, tuple, or vector", .{});
+                    if (object_ty.zigTypeTag(mod) == .ErrorUnion) {
+                        try sema.errNote(block, arg_src, msg, "consider using 'try', 'catch', or 'if'", .{});
+                    }
                     break :msg msg;
                 };
                 return sema.failWithOwnedErrorMsg(block, msg);

test/cases/compile_errors/for_loop_error_union.zig created+15

...	@@ -0,0 +1,15 @@
1	fn b() !u32 {
2	return 2;
3	}
4
5	export fn a() void {
6	for (b()) \|_\| {}
7	}
8
9	// error
10	// backend=stage2
11	// target=native
12	//
13	// :6:11: error: type '@typeInfo(@typeInfo(@TypeOf(tmp.b)).Fn.return_type.?).ErrorUnion.error_set!u32' is not indexable and not a range
14	// :6:11: note: for loop operand must be a range, array, slice, tuple, or vector
15	// :6:11: note: consider using 'try', 'catch', or 'if'