Stop pirating Base._searchindex and Base._rsearchindex (#9)

Before, these methods were extended with new signatures using big unions.
These big unions included Base types, which meant that certain methodinstances
using concrete types of Base was being invalidated unnecessarily.

This PR stops the type piracy, cutting invalidations from 2000 -> 362.

Author: jakobnissen

src/search.jl

@@ -77,12 +77,30 @@ end
 # The following functions require julia#37283 in Julia 1.6, which
 # allow us to search byte arrays (applied to codeunits(s)).
 @static if VERSION ≥ v"1.6.0-DEV.1341"
-    function Base._searchindex(s::Union{StringViewAndSub,StringAndSub}, t::Union{StringViewAndSub,StringAndSub}, i::Integer)
+    # Split into two identical methods to avoid pirating Base's methods, leading to ~370 invalidations.
+    function Base._searchindex(s::StringViewAndSub, t::Union{StringViewAndSub,StringAndSub}, i::Integer)
+        searchindex_internal(s, t, i)
+    end
+
+    function Base._searchindex(s::Union{StringViewAndSub,StringAndSub}, t::StringViewAndSub, i::Integer)
+        searchindex_internal(s, t, i)
+    end
+
+    function searchindex_internal(s::Union{StringViewAndSub,StringAndSub}, t::Union{StringViewAndSub,StringAndSub}, i::Integer)
         # Check for fast case of a single byte
         lastindex(t) == 1 && return something(findnext(isequal(t[1]), s, i), 0)
         Base._searchindex(codeunits(s), codeunits(t), i)
     end
-    function Base._rsearchindex(s::Union{StringViewAndSub,StringAndSub}, t::Union{StringViewAndSub,StringAndSub}, i::Integer)
+
+    function Base._rsearchindex(s::StringViewAndSub, t::Union{StringViewAndSub,StringAndSub}, i::Integer)
+        rsearchindex_internal(s, t, i)
+    end
+
+    function Base._rsearchindex(s::Union{StringViewAndSub,StringAndSub}, t::StringViewAndSub, i::Integer)
+        rsearchindex_internal(s, t, i)
+    end
+
+    function rsearchindex_internal(s::Union{StringViewAndSub,StringAndSub}, t::Union{StringViewAndSub,StringAndSub}, i::Integer)
         # Check for fast case of a single byte
         if lastindex(t) == 1
             return something(findprev(isequal(t[1]), s, i), 0)