Add @! macro

src/BangBang.jl

@@ -4,6 +4,7 @@ module BangBang
 @doc read(joinpath(dirname(@__DIR__), "README.md"), String) BangBang
 
 export
+    @!,
     append!!,
     delete!!,
     empty!!,
@@ -29,6 +30,7 @@ include("core.jl")
 include("base.jl")
 include("linearalgebra.jl")
 include("initials.jl")
+include("macro.jl")
 
 function __init__()
     @require StaticArrays="90137ffa-7385-5640-81b9-e52037218182" begin

src/core.jl

@@ -16,6 +16,16 @@ pure(::typeof(pushfirst!)) = NoBang.pushfirst
 pure(::typeof(_setproperty!)) = NoBang.setproperty
 pure(::typeof(mul!)) = NoBang.mul
 
+_maybb(mutate) = something(_asbb(mutate), mutate)
+_asbb(::Any) = nothing
+
+_asbb(::typeof(push!)) = push!!
+_asbb(::typeof(append!)) = append!!
+_asbb(::typeof(pushfirst!)) = pushfirst!!
+_asbb(::typeof(mul!)) = mul!!
+_asbb(::typeof(delete!)) = delete!!
+_asbb(::typeof(empty!)) = empty!!
+
 const MaybeMutableContainer = Union{
     AbstractArray,
     AbstractDict,

src/macro.jl

@@ -0,0 +1,24 @@
+"""
+  @! expr
+
+Convert all supported mutating calls to double bang equivalent.
+
+# Examples
+```jldoctest
+julia> using BangBang
+
+julia> @! push!(empty!((0, 1)), 2, 3)
+(2, 3)
+```
+"""
+macro !(expr)
+    foldexpr(expr) do x
+        if Meta.isexpr(x, :call)
+            return Expr(:call, Expr(:call, _maybb, x.args[1]), x.args[2:end]...)
+        end
+        return x
+    end |> esc
+end
+
+foldexpr(f, x) = x
+foldexpr(f, ex::Expr) = f(Expr(ex.head, foldexpr.(f, ex.args)...))

test/test_macro.jl

@@ -0,0 +1,10 @@
+module TestMacro
+
+include("preamble.jl")
+
+@testset begin
+    @test (@! push!(empty!([0, 1]), 2, 3)) == [2, 3]
+    @test (@! push!(empty!((0, 1)), 2, 3)) == (2, 3)
+end
+
+end  # module