limit TimeType subtraction. replaces #49805

Author: JeffBezanson

stdlib/Dates/src/arithmetic.jl

@@ -6,8 +6,9 @@
 
 # TimeType arithmetic
 (+)(x::TimeType) = x
-(-)(x::T, y::T) where {T<:TimeType} = x.instant - y.instant
-(-)(x::T, y::T) where {T<:AbstractDateTime} = x.instant - y.instant
+(-)(x::Date, y::Date) = x.instant - y.instant
+(-)(x::Time, y::Time) = x.instant - y.instant
+(-)(x::DateTime, y::DateTime) = x.instant - y.instant
 (-)(x::AbstractDateTime, y::AbstractDateTime) = -(promote(x, y)...)
 
 # Date-Time arithmetic

stdlib/Dates/test/arithmetic.jl

@@ -11,6 +11,10 @@ using Dates
     @test Dates.CompoundPeriod(a - b) == Dates.Hour(12)
 end
 
+@testset "TimeType arithmetic" begin
+    @test_throws MethodError DateTime(2023, 5, 2) - Date(2023, 5, 1)
+end
+
 @testset "Wrapping arithmetic for Months" begin
     # This ends up being trickier than expected because
     # the user might do 2014-01-01 + Month(-14)