Added Compat.AbstractDateTime (#443)

* Added Compat.AbstractDateTime.

* Added tests and README entry for AbstractDateTime.

* Added DateTime subtype check.

Author: rofinn

README.md

@@ -301,7 +301,7 @@ Currently, the `@compat` macro supports the following syntaxes:
 
 ## New types
 
-Currently, no new exported types are introduced by Compat.
+* `Compat.AbstractDateTime` is an alias for `Compat.Dates.AbstractDateTime` as of ([#25227]) and `Compat.Dates.TimeType` prior to that.
 
 ## Developer tips
 

src/Compat.jl

@@ -770,6 +770,12 @@ else
     import Dates
 end
 
+if VERSION < v"0.7.0-DEV.3216"
+    const AbstractDateTime = Compat.Dates.TimeType
+else
+    const AbstractDateTime = Compat.Dates.AbstractDateTime
+end
+
 if VERSION < v"0.7.0-DEV.3052"
     const Printf = Base.Printf
 else

test/runtests.jl

@@ -1083,6 +1083,10 @@ end
 # 0.7.0-DEV.3172
 @test replace("abcb", "b"=>"c") == "accc"
 @test replace("abcb", "b"=>"c", count=1) == "accb"
+# 0.7.0-DEV.3216
+@test Compat.AbstractDateTime === (isdefined(Compat.Dates, :AbstractDateTime) ? Compat.Dates.AbstractDateTime : Compat.Dates.TimeType)
+@test Compat.AbstractDateTime <: Compat.Dates.TimeType
+@test Compat.Dates.DateTime <: Compat.AbstractDateTime
 
 # 0.7.0-DEV.3025
 let c = CartesianIndices(1:3, 1:2), l = LinearIndices(1:3, 1:2)