Add support for property destructuring in @compat macro (#768)

* add property destructuring assignment to `@compat` * update readme * one more test * Update src/compatmacro.jl Co-authored-by: Alex Arslan <ararslan@comcast.net> * hoist guard adn use Meta.isexpr * bump minor version (new feature) Co-authored-by: Alex Arslan <ararslan@comcast.net>
JuliaLang · Apr 11, 2022 · 3ae185f · 3ae185f · ararslan · Apr 11, 2022
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diff --git a/Project.toml b/Project.toml
@@ -1,6 +1,6 @@
 name = "Compat"
 uuid = "34da2185-b29b-5c13-b0c7-acf172513d20"
-version = "3.42.0"
+version = "3.43.0"
 
 [deps]
 Base64 = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"

diff --git a/README.md b/README.md
@@ -54,6 +54,8 @@ changes in `julia`.
 
 ## Supported features
 
+* `@compat (; a, b) = (; c=1, b=2, a=3)` supports property descturing assignment syntax ([#39285]).
+
 * `allequal`, the opposite of `allunique` ([#43354]). (since Compat 3.42.0)
 
 * `eachsplit` for iteratively performing split(str). ([#39245]). (since Compat 3.41.0)
@@ -293,3 +295,4 @@ Note that you should specify the correct minimum version for `Compat` in the
 [#41312]: https://github.com/JuliaLang/julia/pull/41312
 [#41328]: https://github.com/JuliaLang/julia/pull/41328
 [#43354]: https://github.com/JuliaLang/julia/pull/43354
+[#39285]: https://github.com/JuliaLang/julia/pull/39285
diff --git a/src/compatmacro.jl b/src/compatmacro.jl
@@ -16,6 +16,15 @@ function _compat(ex::Expr)
         end
     end
 
+    # https://github.com/JuliaLang/julia/pull/39285
+    @static if VERSION < v"1.7.0-DEV.364"
+        if Meta.isexpr(ex, :(=)) && Meta.isexpr(ex.args[1], :tuple) &&
+            Meta.isexpr(ex.args[1].args[1], :parameters)
+
+            ex = _destructure_named_tuple(ex)
+        end
+    end
+
     return Expr(ex.head, map(_compat, ex.args)...)
 end
 
@@ -94,3 +103,16 @@ function _assign_implicit_keywords(ex::Expr)
 
     return ex
 end
+
+function _destructure_named_tuple(ex::Expr)
+    ex.args[1].args[1] isa Expr && ex.args[1].args[1].head === :parameters
+    values = ex.args[2]
+    parameters = ex.args[1].args[1].args
+    ex = Expr(:block)
+    for p in parameters
+        asgn = Expr(:(=), p, Expr(:., values, QuoteNode(p)))
+        push!(ex.args, asgn)
+    end
+    push!(ex.args, values)
+    return ex
+end
diff --git a/test/runtests.jl b/test/runtests.jl
@@ -1088,6 +1088,18 @@ end
     @test (@compat (; nested.x.x)) == (; x=3)
 end
 
+# https://github.com/JuliaLang/julia/pull/39285
+@testset "property destructuring assignment" begin
+    nt = (; a=1, b=2, c=3)
+    @compat (; c, b) = nt
+    @test c == nt.c
+    @test b == nt.b
+
+    @compat (; x) = X(1)
+    @test x == 1
+end
+
+
 # https://github.com/JuliaLang/julia/pull/34595
 @testset "include(mapexpr::Function, ...)" begin
     m = Module()