Add fetch(::Task) (#549)

README.md

@@ -297,6 +297,8 @@ Currently, the `@compat` macro supports the following syntaxes:
 
 * `squeeze` with `dims` as keyword argument ([#26660]).
 
+* `fetch` for `Task`s ([#25940]).
+
 * `Compat.qr` takes `pivot` as a `Val` _instance_ and keyword argument `full` ([#22475], [#24279]).
 
 * `Compat.rmul!` provides a subset of the functionality of `LinearAlgebra.rmul!` for
@@ -618,6 +620,7 @@ includes this fix. Find the minimum version from there.
 [#25873]: https://github.com/JuliaLang/julia/issues/25873
 [#25896]: https://github.com/JuliaLang/julia/issues/25896
 [#25935]: https://github.com/JuliaLang/julia/issues/25935
+[#25940]: https://github.com/JuliaLang/julia/issues/25940
 [#25959]: https://github.com/JuliaLang/julia/issues/25959
 [#25989]: https://github.com/JuliaLang/julia/issues/25989
 [#25990]: https://github.com/JuliaLang/julia/issues/25990

src/Compat.jl

@@ -1854,6 +1854,12 @@ elseif VERSION >= v"0.7.0-DEV.3665" # mul1! -> rmul!
     using LinearAlgebra: rmul!
 end
 
+@static if VERSION < v"0.7.0-DEV.3936"
+    Base.fetch(t::Task) = wait(t)
+else
+    import Base: fetch
+end
+
 # https://github.com/JuliaLang/julia/pull/27077
 @static if VERSION < v"0.7.0-DEV.5087"
     export isletter

test/runtests.jl

@@ -1702,6 +1702,13 @@ let A = [1 2; 3 4]
     @test Compat.rmul!(Diagonal(A), Diagonal([2, 1])) == Diagonal([8, 120])
 end
 
+# 0.7.0-DEV.3936
+@test let ct = current_task(), t = @task true
+    schedule(ct)
+    yieldto(t)
+    fetch(t)
+end
+
 # 0.7.0-DEV.5087
 @test isletter('a')
 @test isletter('β')