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 >>

1 files changed, 1 insertions, 3 deletions

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) ->