test new subtype of AbstractString with thisind etc. methods

Author: nsajko

test/no_invalidations.jl

@@ -58,6 +58,15 @@ end
             @test test_expr((n -> :(function Base.show(::IO, ::$n) end)), S) broken=(S ∈ broken)
         end
     end
+    @testset "new subtype of `AbstractString`" begin
+        @testset "index-related" begin
+            fs = (thisind, prevind, nextind)
+            broken = (thisind, prevind, nextind)
+            @testset "f: $f" for f ∈ fs
+                @test test_expr((n -> :(function Base.$f(::$n, ::Int) end)), AbstractString) broken=(f ∈ broken)
+            end
+        end
+    end
     @testset "new subtype of `Integer`" begin
         int_types = (Bool, Int8, UInt8, Int16, UInt16, Int, UInt, BigInt)
         @testset "construction of old int type from new type" begin