Where are control flow labels fully documented?

Tamas_Papp · May 23, 2026, 7:13am

The documentation of @label is rather sparse. I am looking for a comprehensive list of

which forms can be preceded by @label my_label (apparently begin, for, what else?)
which forms accept labels (eg break and @goto, what else?)

Tamas_Papp · May 23, 2026, 7:23am

Ah, silly me, the feature is not even in 1.13, master documents is properly.

github.com/JuliaLang/julia

syntax: Add labeled block break (#60481)

master ← kf/breakblocks

merged 03:37PM - 24 Jan 26 UTC

Keno

+1119 -341

This is a redo of #60367 taking into account various feedback on that PR. In par…ticular, it seemed like people strongly disliked the `break break` syntax for two primary reasons: 1. It scales poorly to multiple loops `break break break break` 2. It introduced footguns if extra loops are introduced between the loop and the break. Instead, the consensus seemed to be that labeled break should be the only facility available. Thus, this implements a proper labeled break facility that looks as follows: ``` @label :name for i = 1:10 for j = 1:10 break :name (i, j) end end # evaluate to `(1,1) ``` The idea is to re-use the `@label` macro for now, but possibly promote this to syntax in a future version if it gains widespread use. Note that parser changes are still required, since the `break` syntax is currently an error. However, compat.jl could provide `@goto break name val`, which parses fine. `continue` is extended with label support as well: ``` @label :outer while true for i = 1:10 a[i] && continue :outer end [...] end ``` However, the feature is not restricted to loops. A particular use case is to replace cleanup blocks written like ``` cond1 && @goto error cond2 && @goto error return true @label error error("foo") ``` by a labeled begin/end block: ``` @label :error begin cond1 && break :error cond2 && break :error return true end error("foo") ``` This doesn't save much typing work, but it makes this kind of pattern much more structured, e.g. for code-folding in IDEs. A similar pattern replaces the `for-then` construction originally proposed: ``` result = @label :result begin for x in arr pred(x) && break :result x end default end ``` For convenience, the label may be ommitted, in which case it defaults to `_`, i.e. the above can be written as: ``` result = @label begin for x in arr pred(x) && break _ x end default end ``` I've taken the liberty of converting some base code for testing and to give an idea of what the syntax looks like in practice, but didn't go through particularly comprehensively. These changes should be considered extended usage examples. Largely written by Claude, and I haven't looked at the implementation particularly carefully yet - for now I'm just interested in discussion of the syntax.

Sorry for the noise, I was working in nightly and reading the 1.12 docs

Topic		Replies	Views
How to use the macro @label and @goto General Usage	7	4281	June 4, 2022
How to break several nested 'for' loop in one 'if' General Usage	18	5555	May 3, 2021
Named for loops? New to Julia	3	830	August 15, 2019
Does `@label`/`@goto` introduce scope like loop blocks? General Usage	5	278	August 24, 2025
Side discussion on gotos Internals & Design	4	1610	October 26, 2018

Where are control flow labels fully documented?

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