fix #35272, searchsorted(3:-1:1, 2.5, rev=true) (#35274)

Author: rfourquet

base/sort.jl

@@ -262,7 +262,11 @@ function searchsortedlast(a::AbstractRange{<:Integer}, x::Real, o::DirectOrderin
     elseif h < 0 && x <= last(a)
         lastindex(a)
     else
-        fld(floor(Integer, x) - first(a), h) + 1
+        if o isa ForwardOrdering
+            fld(floor(Integer, x) - first(a), h) + 1
+        else
+            fld(ceil(Integer, x) - first(a), h) + 1
+        end
     end
 end
 
@@ -280,7 +284,11 @@ function searchsortedfirst(a::AbstractRange{<:Integer}, x::Real, o::DirectOrderi
     elseif h < 0 && x < last(a)
         lastindex(a) + 1
     else
-        -fld(floor(Integer, -x) + first(a), h) + 1
+        if o isa ForwardOrdering
+            -fld(floor(Integer, -x) + first(a), h) + 1
+        else
+            -fld(ceil(Integer, -x) + first(a), h) + 1
+        end
     end
 end
 

test/sorting.jl

@@ -177,6 +177,17 @@ end
             end
         end
     end
+    @testset "issue #35272" begin
+        for v0 = (3:-1:1, 3.0:-1.0:1.0), v = (v0, collect(v0))
+            @test searchsorted(v, 3, rev=true) == 1:1
+            @test searchsorted(v, 3.0, rev=true) == 1:1
+            @test searchsorted(v, 2.5, rev=true) == 2:1
+            @test searchsorted(v, 2, rev=true) == 2:2
+            @test searchsorted(v, 1.2, rev=true) == 3:2
+            @test searchsorted(v, 1, rev=true) == 3:3
+            @test searchsorted(v, 0.1, rev=true) == 4:3
+        end
+    end
 end
 # exercise the codepath in searchsorted* methods for ranges that check for zero step range
 struct ConstantRange{T} <: AbstractRange{T}