Improve inference results in LineEdit

Author: timholy

stdlib/REPL/src/LineEdit.jl

@@ -107,7 +107,7 @@ end
 # the default mark is 0
 getmark(s) = max(0, buffer(s).mark)
 
-const Region = Pair{<:Integer,<:Integer}
+const Region = Pair{Int,Int}
 
 _region(s) = getmark(s) => position(s)
 region(s) = Pair(extrema(_region(s))...)
@@ -201,7 +201,7 @@ end
 beep(::ModeState) = nothing
 cancel_beep(::ModeState) = nothing
 
-for f in [:terminal, :on_enter, :add_history, :buffer, :(Base.isempty),
+for f in [:terminal, :on_enter, :add_history, :_buffer, :(Base.isempty),
           :replace_line, :refresh_multi_line, :input_string, :update_display_buffer,
           :empty_undo, :push_undo, :pop_undo, :options, :cancel_beep, :beep,
           :deactivate_region, :activate_region, :is_region_active, :region_active]
@@ -2355,10 +2355,11 @@ function run_interface(terminal::TextTerminal, m::ModalInterface, s::MIState=ini
     end
 end
 
-buffer(s::PromptState) = s.input_buffer
-buffer(s::SearchState) = s.query_buffer
-buffer(s::PrefixSearchState) = s.response_buffer
-buffer(s::IOBuffer) = s
+buffer(s) = _buffer(s)::IOBuffer
+_buffer(s::PromptState) = s.input_buffer
+_buffer(s::SearchState) = s.query_buffer
+_buffer(s::PrefixSearchState) = s.response_buffer
+_buffer(s::IOBuffer) = s
 
 position(s::Union{MIState,ModeState}) = position(buffer(s))