Merge pull request #17 from JuliaOpt/bl/hygiene

Add hygiene tests

src/rewrite.jl

@@ -56,12 +56,14 @@ julia> MutableArithmetics.rewrite_generator(:(i for i in 1:2 if isodd(i)), i ->
 ```
 """
 function rewrite_generator(ex, inner)
+    # `i + j for i in 1:2 for j in 1:2` is a `flatten` expression
     if isexpr(ex, :flatten)
         return rewrite_generator(ex.args[1], inner)
     end
     if !isexpr(ex, :generator)
         return inner(ex)
     end
+    # `i + j for i in 1:2, j in 1:2` is a `generator` expression
     function itrsets(sets)
         if isa(sets, Expr)
             return sets
@@ -98,7 +100,7 @@ _is_sum(s::Symbol) = (s == :sum) || (s == :∑) || (s == :Σ)
 function _parse_generator(x::Expr, aff::Symbol, lcoeffs, rcoeffs, new_var=gensym())
     @assert isexpr(x,:call)
     @assert length(x.args) > 1
-    @assert isexpr(x.args[2],:generator) || isexpr(x.args[2],:flatten)
+    @assert isexpr(x.args[2], :generator) || isexpr(x.args[2], :flatten)
     header = x.args[1]
     if _is_sum(header)
         _parse_generator_sum(x.args[2], aff, lcoeffs, rcoeffs, new_var)
@@ -117,17 +119,25 @@ end
 
 _is_complex_expr(ex) = isa(ex, Expr) && !isexpr(ex, :ref)
 
-function rewrite_and_return(x)
-    variable, code = rewrite(x)
-    return :($code; $variable)
-end
 function rewrite(x)
     variable = gensym()
-    new_variable, code = rewrite_to(x, variable)
-    return new_variable, :($variable = MutableArithmetics.Zero(); $code)
+    code = rewrite_and_return(x)
+    return variable, :($variable = $code)
+end
+function rewrite_and_return(x)
+    variable = gensym()
+    output_variable, code = _rewrite_to(x, variable)
+    # We need to use `let` because `rewrite(:(sum(i for i in 1:2))`
+    return quote
+        let
+            $variable = MutableArithmetics.Zero()
+            $code
+            $output_variable
+        end
+    end
 end
 
-rewrite_to(x, variable::Symbol) = _rewrite(x, variable, [], [])
+_rewrite_to(x, variable::Symbol) = _rewrite(x, variable, [], [])
 
 function _is_comparison(ex::Expr)
     if isexpr(ex, :comparison)
@@ -209,7 +219,7 @@ function _rewrite(x, aff::Symbol, lcoeffs::Vector, rcoeffs::Vector, new_var::Sym
                 for i in 2:length(x.args)
                     if _is_complex_expr(x.args[i])
                         s = gensym()
-                        new_var_, parsed = rewrite_to(x.args[i], s)
+                        new_var_, parsed = _rewrite_to(x.args[i], s)
                         push!(blk.args, :($s = MutableArithmetics.Zero(); $parsed))
                         x.args[i] = new_var_
                     else
@@ -226,7 +236,7 @@ function _rewrite(x, aff::Symbol, lcoeffs::Vector, rcoeffs::Vector, new_var::Sym
             if x.args[3] == 2
                 blk = Expr(:block)
                 s = gensym()
-                new_var_, parsed = rewrite_to(x.args[2], s)
+                new_var_, parsed = _rewrite_to(x.args[2], s)
                 push!(blk.args, :($s = MutableArithmetics.Zero(); $parsed))
                 push!(blk.args, :($new_var = MutableArithmetics.add_mul!(
                     $aff, $(Expr(:call, :*, lcoeffs..., new_var_, new_var_,
@@ -239,7 +249,7 @@ function _rewrite(x, aff::Symbol, lcoeffs::Vector, rcoeffs::Vector, new_var::Sym
             else
                 blk = Expr(:block)
                 s = gensym()
-                new_var_, parsed = rewrite_to(x.args[2], s)
+                new_var_, parsed = _rewrite_to(x.args[2], s)
                 push!(blk.args, :($s = MutableArithmetics.Zero(); $parsed))
                 push!(blk.args, :($new_var = MutableArithmetics.add_mul!(
                     $aff, $(Expr(:call, :*, lcoeffs...,