Revise Integration

TypeContracts ships a weak-dependency extension for Revise.jl. When both packages are loaded in an interactive session, contract conformance is re-checked automatically after each revision cycle — so a violation introduced by editing a method shows up immediately as a warning, without having to restart Julia or re-run @verify manually.

Activation

No configuration is required. Loading both packages is sufficient:

using Revise        # must come first so the extension loads
using TypeContracts

Or in any order that results in both being in scope — for example, inside a startup.jl that always loads Revise, followed by using TypeContracts in your project.

The extension is a weak dependency: if Revise is not loaded, TypeContracts behaves exactly as without it. No code changes are needed to make a package Revise-compatible.

What gets re-checked

After each revision cycle the extension re-checks every type and module that was registered during precompile time:

Registration	What is re-checked
@verify T	T itself
@verify_all	all concrete subtypes of registered contract types defined in the calling module

A warning (not an error) is emitted for each violation so the REPL session stays alive:

┌ Warning: Contract violation detected by Revise
│   type = Circle
│   msg = Type Circle does not satisfy interface contract.
│   Missing or incorrect methods:
│     area(::Self) :: Float64 — return String ⊄ Float64  [required by AbstractShape]
└ @ TypeContracts ...

Example

# file: shapes.jl
module Shapes
using TypeContracts

abstract type AbstractShape end
function area end

@contract AbstractShape begin
    area(::Self) :: Float64
end

struct Circle <: AbstractShape
    radius::Float64
end

area(c::Circle)::Float64 = π * c.radius^2

@verify Circle

end

In a REPL session:

julia> using Revise, TypeContracts
julia> includet("shapes.jl")   # Revise tracks the file

Now edit shapes.jl to break the contract — for example change area to return a String:

area(c::Circle) = "oops"

On the next REPL interaction, Revise picks up the change and the extension fires:

┌ Warning: Contract violation detected by Revise
│   type = Shapes.Circle
│   msg = Type Circle does not satisfy interface contract.
│   ...
└ @ TypeContracts ...

Fix the method, and the warning disappears on the next revision cycle.

Notes

• The check fires on any file change tracked by Revise, not only changes to the files that define the checked types. This is intentional: a method added elsewhere could satisfy or break a contract.

• Types that appear in both @verify T and a @verify_all module are checked twice — once for each registration. This is harmless.

• The extension uses Revise.add_callback with all=true. The callback is registered in the extension's __init__ and runs asynchronously via Base.invokelatest after each revision cycle, so it cannot block the REPL or crash the session.