diff --git a/stdlib/REPL/src/LineEdit.jl b/stdlib/REPL/src/LineEdit.jl
index 2084a8d2e4bf5..c34728b63d373 100644
--- a/stdlib/REPL/src/LineEdit.jl
+++ b/stdlib/REPL/src/LineEdit.jl
@@ -3,8 +3,9 @@
 module LineEdit
 
 import ..REPL
-using ..Terminals
+using REPL: AbstractREPL
 
+using ..Terminals
 import ..Terminals: raw!, width, height, cmove, getX,
                        getY, clear_line, beep
 
@@ -13,6 +14,8 @@ using Base: something
 
 abstract type TextInterface end
 abstract type ModeState end
+abstract type HistoryProvider end
+abstract type CompletionProvider end
 
 export run_interface, Prompt, ModalInterface, transition, reset_state, edit_insert, keymap
 
@@ -31,11 +34,11 @@ mutable struct Prompt <: TextInterface
     # Same as prefix except after the prompt
     prompt_suffix::Union{String,Function}
     keymap_dict::Dict{Char}
-    repl # ::AbstractREPL
-    complete # ::REPLCompletionProvider
+    repl::Union{AbstractREPL,Nothing}
+    complete::CompletionProvider
     on_enter::Function
     on_done::Function
-    hist # ::REPLHistoryProvider
+    hist::HistoryProvider
     sticky::Bool
 end
 
@@ -141,9 +144,6 @@ function input_string_newlines_aftercursor(s::PromptState)
     return count(c->(c == '\n'), rest)
 end
 
-abstract type HistoryProvider end
-abstract type CompletionProvider end
-
 struct EmptyCompletionProvider <: CompletionProvider end
 struct EmptyHistoryProvider <: HistoryProvider end
 
@@ -1602,9 +1602,16 @@ const escape_defaults = merge!(
     AnyDict("\e[$(c)l" => nothing for c in 1:20)
     )
 
+mutable struct HistoryPrompt <: TextInterface
+    hp::HistoryProvider
+    complete::CompletionProvider
+    keymap_dict::Dict{Char,Any}
+    HistoryPrompt(hp) = new(hp, EmptyCompletionProvider())
+end
+
 mutable struct SearchState <: ModeState
     terminal::AbstractTerminal
-    histprompt # ::HistoryPrompt
+    histprompt::HistoryPrompt
     #rsearch (true) or ssearch (false)
     backward::Bool
     query_buffer::IOBuffer
@@ -1617,6 +1624,8 @@ mutable struct SearchState <: ModeState
         new(terminal, histprompt, backward, query_buffer, response_buffer, false, InputAreaState(0,0))
 end
 
+init_state(terminal, p::HistoryPrompt) = SearchState(terminal, p, true, IOBuffer(), IOBuffer())
+
 terminal(s::SearchState) = s.terminal
 
 function update_display_buffer(s::SearchState, data)
@@ -1654,18 +1663,20 @@ function reset_state(s::SearchState)
     nothing
 end
 
-mutable struct HistoryPrompt <: TextInterface
-    hp # ::HistoryProvider
-    complete # ::CompletionProvider
+# a meta-prompt that presents itself as parent_prompt, but which has an independent keymap
+# for prefix searching
+mutable struct PrefixHistoryPrompt <: TextInterface
+    hp::HistoryProvider
+    parent_prompt::Prompt
+    complete::CompletionProvider
     keymap_dict::Dict{Char,Any}
-    HistoryPrompt(hp) = new(hp, EmptyCompletionProvider())
+    PrefixHistoryPrompt(hp, parent_prompt) =
+        new(hp, parent_prompt, EmptyCompletionProvider())
 end
 
-init_state(terminal, p::HistoryPrompt) = SearchState(terminal, p, true, IOBuffer(), IOBuffer())
-
 mutable struct PrefixSearchState <: ModeState
     terminal::AbstractTerminal
-    histprompt # ::HistoryPrompt
+    histprompt::PrefixHistoryPrompt
     prefix::String
     response_buffer::IOBuffer
     ias::InputAreaState
@@ -1678,6 +1689,8 @@ mutable struct PrefixSearchState <: ModeState
         new(terminal, histprompt, prefix, response_buffer, InputAreaState(0,0), 0)
 end
 
+init_state(terminal, p::PrefixHistoryPrompt) = PrefixSearchState(terminal, p, "", IOBuffer())
+
 function show(io::IO, s::PrefixSearchState)
     print(io, "PrefixSearchState ", isdefined(s,:parent) ?
      string("(", s.parent, " active)") : "(no parent)", " for ",
@@ -1696,19 +1709,6 @@ end
 
 input_string(s::PrefixSearchState) = String(take!(copy(s.response_buffer)))
 
-# a meta-prompt that presents itself as parent_prompt, but which has an independent keymap
-# for prefix searching
-mutable struct PrefixHistoryPrompt <: TextInterface
-    hp # ::HistoryProvider
-    parent_prompt::Prompt
-    complete # ::CompletionProvider
-    keymap_dict::Dict{Char,Any}
-    PrefixHistoryPrompt(hp, parent_prompt) =
-        new(hp, parent_prompt, EmptyCompletionProvider())
-end
-
-init_state(terminal, p::PrefixHistoryPrompt) = PrefixSearchState(terminal, p, "", IOBuffer())
-
 write_prompt(terminal, s::PrefixSearchState) = write_prompt(terminal, s.histprompt.parent_prompt)
 prompt_string(s::PrefixSearchState) = prompt_string(s.histprompt.parent_prompt.prompt)
 
diff --git a/stdlib/REPL/src/REPL.jl b/stdlib/REPL/src/REPL.jl
index 5259a4fd717e8..b892eb7b3e6eb 100644
--- a/stdlib/REPL/src/REPL.jl
+++ b/stdlib/REPL/src/REPL.jl
@@ -36,6 +36,8 @@ import Base:
 include("Terminals.jl")
 using .Terminals
 
+abstract type AbstractREPL end
+
 include("LineEdit.jl")
 using .LineEdit
 import ..LineEdit:
@@ -66,8 +68,6 @@ function __init__()
     Base.REPL_MODULE_REF[] = REPL
 end
 
-abstract type AbstractREPL end
-
 answer_color(::AbstractREPL) = ""
 
 const JULIA_PROMPT = "julia> "
@@ -481,15 +481,15 @@ function complete_line(c::LatexCompletions, s)
 end
 
 mutable struct REPLHistoryProvider <: HistoryProvider
-    history::Array{String,1}
+    history::Vector{String}
     history_file::Union{Nothing,IO}
     start_idx::Int
     cur_idx::Int
     last_idx::Int
     last_buffer::IOBuffer
     last_mode::Union{Nothing,Prompt}
-    mode_mapping::Dict
-    modes::Array{Symbol,1}
+    mode_mapping::Dict{Symbol,Prompt}
+    modes::Vector{Symbol}
 end
 REPLHistoryProvider(mode_mapping) =
     REPLHistoryProvider(String[], nothing, 0, 0, -1, IOBuffer(),