Merge pull request #84 from JuliaDebug/teh/nothunk

Handle expressions that lower to nothing

Author: timholy

src/JuliaInterpreter.jl

@@ -388,7 +388,9 @@ function prepare_thunk(mod::Module, thunk::Expr, recursive=false)
         thunk = Meta.lower(mod, Expr(:block, nothing, thunk))
         framecode = JuliaFrameCode(mod, thunk.args[1])
     else
-        return prepare_thunk(mod, Meta.lower(mod, thunk), true)
+        lwr = Meta.lower(mod, thunk)
+        isa(lwr, Expr) && return prepare_thunk(mod, lwr, true)
+        return nothing
     end
     return prepare_locals(framecode, [])
 end

test/interpret.jl

@@ -270,3 +270,7 @@ let TT = Union{UInt8, Int8}
     pa = pointer(a)
     @interpret unsafe_store!(pa, 0x1, 2)
 end
+
+# Some expression can appear nontrivial but lower to nothing
+@test isa(JuliaInterpreter.prepare_thunk(Main, :(@static if ccall(:jl_get_UNAME, Any, ()) == :NoOS 1+1 end)), Nothing)
+@test isa(JuliaInterpreter.prepare_thunk(Main, :(Base.BaseDocs.@kw_str "using")), Nothing)