I tried to thin this to the bare bones; please help me with what I’m missing. Given (the somewhat ludicrous, now): pub const Foo = struct { const Self = @This(); pub fn bar(self: *Self) Foo { _ = self; return .{}; } pub fn bam(self: *Self) Foo { _ = self; return .{}; } }; I can do this: …

Hi ! This is completely intended ! When chaining function in your case, you are asking in your function to pass a *Self pointer, that is a pointer to a mutable value. However, when immediately using return values from functions, the value is immutable. For example the following would not work : c…

Oops, I was conflating my trimmed posted code with my original code again, and, even then, I was confusing unrelated things; sorry for the noise, but your post is a good reminder, of course.

[image] FObersteiner: I don’t think you need @This in the OP’s example since you don’t have an anonymous struct. Ah, great! Actually, my “real” code is @This-less, but I hadn’t worked out the real value of @This, yet (for anonymous structs), and I thought I’d make my posted code look more li…

[image] mnemnion: Or you can return the struct as a mutable pointer, *Foo in this case. This is the case that I was thinking about in my follow-up about returning references/pointers to locals that will go out of scope. I know you can do what you say, here, but remind me again where the gotc…

[image] jmctagger: I know you can do what you say, here, but remind me again where the gotcha is? You must not return a pointer to stack memory from a function, because that pointer is no longer valid. So if an initializer returns a *Foo, it had better take an Allocator so that the pointer l…

[image] mnemnion: You must not return a pointer to stack memory from a function, because that pointer is no longer valid. I’m sorry, this was too obvious. I misinterpreted; of course returning a *Foo will need an allocated Foo, rather than returning a reference to a local-stack Foo. But it’…

[image] jmctagger: However, what I was trying to get ahold of was an “inline” case… There was some discussion about whether inlining should be considered a case of stranding memory. A good argument can be made for both sides, recently the Zig compiler will tag that as a memory violation, so…

[image] mnemnion: It also means no one will strand a pointer by removing the inline keyword, which is all to the good. Right, though I guess removal of the inline could still result in the memory violation flag, as currently happens (as you point out). But it is nice when the world has fewer…

A couple of years ago there was a topic, just in case. [image] Methods chaining Brainstorming If some (or all) functions within a struct return a pointer to self, then we can easily chain methods calls, akin using a pipe in a shell: const std = @import("std…

[image] dee0xeed: A couple of years ago there was a topic, just in case. Yes, thank you for referencing that - I’d read it, and just re-read it. There are some important meatballs in that dialog. There’s also the fluent showcase and conversation that makes foundational use of chaining. In …

[image] jmctagger: My case was more of a “builder” pattern, though - not quite akin to matrix manipulation chains. With enough effort, if you care about it, you can make it possible to write code like this: const e_thing = Thing.create(allocator) .build1(stuff, more_stuff) .keepBuildin…

Simple function chaining

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dee0xeed January 23, 2026, 5:25pm 17

A couple of years ago there was a topic, just in case.