From 205405f0bf1d2fa37d4c8170c11689a2937f5d9c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Tue, 1 Mar 2016 06:23:36 +0100
Subject: Generalize bit string comprehensions

The expression in a bit string comprehension is limited to a
literal bit string expression. That is, the following code
is legal:

  << <<X>> || X <- List >>

but not this code:

  << foo(X) || X <- List >>

The limitation is annoying. For one thing, tools that transform
the abstract format must be careful not to produce code such as:

  << begin
      %% Some instrumentation code.
      <<X>>
     end || X <- List >>

One reason for the limitation could be that we'll get
reduce/reduce conflicts if we try to allow an arbitrary
expression in a bit string comprehension:

  binary_comprehension -> '<<' expr '||' lc_exprs '>>' :
	{bc,?anno('$1'),'$2','$4'}.

Unfortunately, there does not seem to be an easy way to work
around that problem. The best we can do is to allow 'expr_max'
expressions (as in the binary syntax):

  binary_comprehension -> '<<' expr_max '||' lc_exprs '>>' :
	{bc,?anno('$1'),'$2','$4'}.

That will work, but functions calls must be enclosed in
parentheses:

  << (foo(X)) || X <- List >>
---
 lib/tools/src/cover.erl        |  4 +---
 lib/tools/test/cover_SUITE.erl | 29 +++++++++++++++++++++--------
 2 files changed, 22 insertions(+), 11 deletions(-)

(limited to 'lib/tools')

diff --git a/lib/tools/src/cover.erl b/lib/tools/src/cover.erl
index 3732b0fc85..87de31919f 100644
--- a/lib/tools/src/cover.erl
+++ b/lib/tools/src/cover.erl
@@ -2002,9 +2002,7 @@ munge_expr({lc,Line,Expr,Qs}, Vars) ->
     {MungedQs, Vars3} = munge_qualifiers(Qs, Vars2),
     {{lc,Line,MungedExpr,MungedQs}, Vars3};
 munge_expr({bc,Line,Expr,Qs}, Vars) ->
-    {bin,BLine,[{bin_element,EL,Val,Sz,TSL}|Es]} = Expr,
-    Expr2 = {bin,BLine,[{bin_element,EL,Val,Sz,TSL}|Es]},
-    {MungedExpr,Vars2} = munge_expr(Expr2, Vars),
+    {MungedExpr,Vars2} = munge_expr(?BLOCK1(Expr), Vars),
     {MungedQs, Vars3} = munge_qualifiers(Qs, Vars2),
     {{bc,Line,MungedExpr,MungedQs}, Vars3};
 munge_expr({block,Line,Body}, Vars) ->
diff --git a/lib/tools/test/cover_SUITE.erl b/lib/tools/test/cover_SUITE.erl
index b9a9cd5be4..d4b346c407 100644
--- a/lib/tools/test/cover_SUITE.erl
+++ b/lib/tools/test/cover_SUITE.erl
@@ -29,7 +29,7 @@ all() ->
     NoStartStop = [eif,otp_5305,otp_5418,otp_7095,otp_8273,
                    otp_8340,otp_8188,compile_beam_opts,eep37,
 		   analyse_no_beam, line_0, compile_beam_no_file,
-                   otp_13277],
+                   otp_13277, otp_13289],
     StartStop = [start, compile, analyse, misc, stop,
 		 distribution, reconnect, die_and_reconnect,
 		 dont_reconnect_after_stop, stop_node_after_disconnect,
@@ -1253,7 +1253,7 @@ otp_8340(doc) ->
     ["OTP-8340. Bug."];
 otp_8340(suite) -> [];
 otp_8340(Config) when is_list(Config) ->
-    ?line [{{t,1},1},{{t,4},1}] =
+    [{{t,1},1},{{t,2},1},{{t,4},1}] =
         analyse_expr(<<"<< \n"
                        " <<3:2, \n"
                        "   SeqId:62>> \n"
@@ -1547,10 +1547,8 @@ comprehension_8188(Cf) ->
                        "    true]. \n" % 2
                        "  two() -> 2">>, Cf), % 1
 
-    %% The template cannot have a counter since it is not allowed to
-    %% be a block.
     ?line [{{t,1},1},
-           %% {{t,2},2},
+           {{t,2},2},
            {{t,3},1},
            {{t,4},1},
            {{t,5},0},
@@ -1560,7 +1558,7 @@ comprehension_8188(Cf) ->
            {{t,13},2},
            {{t,14},2}] = 
         analyse_expr(<<"<< \n" % 1
-                       " << (X*2) >> || \n" % 2 (now: 0)
+                       " << (X*2) >> || \n" % 2
                        "    <<X>> <= << (case two() of\n"
                        "                     2 -> 1;\n" % 1
                        "                     _ -> 2\n" % 0
@@ -1575,7 +1573,7 @@ comprehension_8188(Cf) ->
                        "two() -> 2">>, Cf),
 
     ?line [{{t,1},1},
-           %% {{t,2},4},
+           {{t,2},4},
            {{t,4},1},
            {{t,6},1},
            {{t,7},0},
@@ -1584,7 +1582,7 @@ comprehension_8188(Cf) ->
            {{t,12},4},
            {{t,13},1}] =
         analyse_expr(<<"<< \n" % 1
-                       " << (2)\n" % 4 (now: 0)
+                       " << (2)\n" % 4
                        "     :(8) >> || \n"
                        "    <<X>> <= << 1,\n" % 1
                        "                (case two() of \n"
@@ -1766,6 +1764,21 @@ otp_13277(Config) ->
     ?line ok = file:delete(File),
     ok.
 
+%% Test general expressions in a binary comprehension.
+otp_13289(Config) ->
+    Test = <<"-module(t).
+              -export([t/0]).
+
+              t() ->
+                  << (id(<<I>>)) || I <- [1,2,3] >>.
+
+              id(I) -> I.
+             ">>,
+    File = cc_mod(t, Test, Config),
+    <<1,2,3>> = t:t(),
+    ok = file:delete(File),
+    ok.
+
 %%--Auxiliary------------------------------------------------------------
 
 analyse_expr(Expr, Config) ->
-- 
cgit v1.2.3