JuliaLang/julia

"@inferred requires a call expression" for do notation

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#59,114 opened on Jul 28, 2025

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 (8 comments) (0 reactions) (0 assignees)Julia (48,709 stars) (5,773 forks)batch import
good first issue

Description

Lambda functions work fine, while the same do-block throws an error:

julia> using Test

julia> @inferred map(x->x, [1,2])
2-element Vector{Int64}:
 1
 2

julia> @inferred map([1,2]) do x
       x
       end
ERROR: LoadError: @inferred requires a call expression

Contributor guide

Tech stack
None
Domain
testing
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Familiarity with JuliaUnderstanding of macros
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70
Research direction
Investigate the implementation of the `@inferred` macro in the Julia standard library (likely in `base/test.jl`). The macro currently expects a call expression but fails for do blocks because the syntax is different. Look at the AST of a do block versus a lambda call to understand the structure. The fix may involve unwrapping the do block to get the actual function call.