From 5b031644e43196144a5824a6d2ade18153779cff Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?John=20H=C3=B6gberg?= <john@erlang.org>
Date: Mon, 14 Jan 2019 17:37:10 +0100
Subject: beam_validator: Add a stable interface for type annotations

---
 lib/compiler/src/beam_ssa_bsm.erl   |  3 ++-
 lib/compiler/src/beam_validator.erl | 28 ++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

(limited to 'lib/compiler/src')

diff --git a/lib/compiler/src/beam_ssa_bsm.erl b/lib/compiler/src/beam_ssa_bsm.erl
index 9631bf3334..466337db0e 100644
--- a/lib/compiler/src/beam_ssa_bsm.erl
+++ b/lib/compiler/src/beam_ssa_bsm.erl
@@ -877,7 +877,8 @@ annotate_context_parameters(F, ModInfo) ->
                                  %% Assertion.
                                  error(conflicting_parameter_types);
                             (K, suitable_for_reuse, Acc) ->
-                                 Acc#{ K => match_context };
+                                 T = beam_validator:type_anno(match_context),
+                                 Acc#{ K => T };
                             (_K, _V, Acc) ->
                                  Acc
                          end, TypeAnno0, ParamInfo),
diff --git a/lib/compiler/src/beam_validator.erl b/lib/compiler/src/beam_validator.erl
index 4943538809..b3c09965cf 100644
--- a/lib/compiler/src/beam_validator.erl
+++ b/lib/compiler/src/beam_validator.erl
@@ -26,6 +26,7 @@
 
 %% Interface for compiler.
 -export([module/2, format_error/1]).
+-export([type_anno/1, type_anno/2, type_anno/3]).
 
 -import(lists, [any/2,dropwhile/2,foldl/3,map/2,foreach/2,reverse/1]).
 
@@ -44,6 +45,33 @@ module({Mod,Exp,Attr,Fs,Lc}=Code, _Opts)
 	    {error,[{atom_to_list(Mod),Es}]}
     end.
 
+%% Provides a stable interface for type annotations, used by certain passes to
+%% indicate that we can safely assume that a register has a given type.
+-spec type_anno(term()) -> term().
+type_anno(atom) -> {atom,[]};
+type_anno(bool) -> bool;
+type_anno({binary,_}) -> term;
+type_anno(cons) -> cons;
+type_anno(float) -> {float,[]};
+type_anno(integer) -> {integer,[]};
+type_anno(list) -> list;
+type_anno(map) -> map;
+type_anno(match_context) -> match_context;
+type_anno(number) -> number;
+type_anno(nil) -> nil.
+
+-spec type_anno(term(), term()) -> term().
+type_anno(atom, Value) -> {atom, Value};
+type_anno(float, Value) -> {float, Value};
+type_anno(integer, Value) -> {integer, Value}.
+
+-spec type_anno(term(), term(), term()) -> term().
+type_anno(tuple, Size, Exact) when is_integer(Size) ->
+    case Exact of
+        true -> {tuple, Size};
+        false -> {tuple, [Size]}
+    end.
+
 -spec format_error(term()) -> iolist().
 
 format_error({{_M,F,A},{I,Off,limit}}) ->
-- 
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