diff --git a/crsn/src/asm/parse/mod.rs b/crsn/src/asm/parse/mod.rs
index a52125c..eaec09d 100644
--- a/crsn/src/asm/parse/mod.rs
+++ b/crsn/src/asm/parse/mod.rs
@@ -53,6 +53,17 @@ pub struct ParserState {
     pub parsing_expr : bool,
 }
 
+impl ParserState {
+    pub fn reset(&mut self) {
+        self.global_reg_aliases.clear();
+        self.reg_aliases.clear();
+        self.reg_alias_stack.clear();
+        self.constants.clear();
+        self.parsing_expr = false;
+        self.const_eval.reset();
+    }
+}
+
 pub fn parse(source: &str, pos: &SourcePosition, parsers: &ParserContext) -> Result<Vec<Op>, CrsnError> {
     let (items, _pos) = expect_list(sexp::parse(source)?, true)?;
 
diff --git a/crsn/src/asm/parse/parse_data.rs b/crsn/src/asm/parse/parse_data.rs
index 3fcd7b6..0aacb9f 100644
--- a/crsn/src/asm/parse/parse_data.rs
+++ b/crsn/src/asm/parse/parse_data.rs
@@ -124,7 +124,7 @@ pub fn parse_data_disp(tok: Sexp, pcx: &ParserContext) -> Result<DataDisp, CrsnE
                 }
 
                 let mut state_mut = pcx.state.borrow_mut();
-                state_mut.const_eval.clear_all();
+                state_mut.const_eval.reset();
 
                 let ticl = state_mut.const_eval.thread_info.clone();
                 op.execute(&ticl, &mut state_mut.const_eval)
diff --git a/crsn/src/builtin/exec.rs b/crsn/src/builtin/exec.rs
index 140f53a..9b5793b 100644
--- a/crsn/src/builtin/exec.rs
+++ b/crsn/src/builtin/exec.rs
@@ -89,7 +89,7 @@ impl OpTrait for BuiltinOp {
                             values.push(state.read(arg)?);
                         }
 
-                        let mut frame2 = StackFrame::new(pos, &values);
+                        let frame2 = StackFrame::new(pos, &values);
                         let handle_val = state.add_coroutine(frame2);
                         state.write(handle, handle_val)?;
 
diff --git a/crsn/src/builtin/parse.rs b/crsn/src/builtin/parse.rs
index 9b3c90b..21ab651 100644
--- a/crsn/src/builtin/parse.rs
+++ b/crsn/src/builtin/parse.rs
@@ -1,4 +1,4 @@
-use sexp::{Atom, Sexp, SourcePosition, atom_qs, atom_s};
+use sexp::{Atom, Sexp, SourcePosition, atom_qs};
 
 use crate::asm::data::literal::{RoutineName};
 use crate::asm::data::reg::parse_reg;
@@ -452,7 +452,7 @@ pub(crate) fn to_sexp(op: &BuiltinOp) -> Sexp {
             if args.is_empty() {
                 sexp::list(&[A("spawn"), A(handle), A(proc)])
             } else {
-                let mut v = vec![A("spawn"), A(handle), A(proc)];
+                let mut v = vec![A("spawn"), A(handle), A(&proc.name)];
                 v.extend(args.iter().map(|r| A(r)));
                 sexp::list(&v)
             }
@@ -473,10 +473,15 @@ mod test {
 
     use sexp::SourcePosition;
 
-    use crate::asm::parse::{parse_instructions, ParserContext};
+    use crate::asm::parse::{parse_instructions, ParserContext, ParserState};
     use crate::asm::parse::sexp_expect::expect_list;
     use crate::builtin::BuiltinOps;
     use crate::module::OpTrait;
+    use std::cell::RefCell;
+    use std::sync::Arc;
+    use crate::runtime::run_thread::{ThreadInfo, ThreadToken, RunState};
+    use crate::runtime::program::Program;
+    use crate::runtime::frame::REG_COUNT;
 
     #[test]
     fn roundtrip() {
@@ -562,13 +567,42 @@ mod test {
 
         let parser = BuiltinOps::new();
 
-        let parsers = &[parser];
+        let parsers = Arc::new(vec![parser]);
+
+        let ti = Arc::new(ThreadInfo {
+            id: ThreadToken(0),
+            uniq: Default::default(),
+            program: Program::new(vec![], parsers.clone()).unwrap(),
+            cycle_time: Default::default(),
+            scheduler_interval: Default::default(),
+            extensions: parsers.clone(),
+        });
+
+        let pcx = ParserContext {
+            parsers: &parsers,
+            state: RefCell::new(ParserState {
+                reg_aliases: Default::default(),
+                reg_alias_stack: vec![],
+                global_reg_aliases: Default::default(),
+                constants: Default::default(),
+
+                // This is a fake thread to pass to constant expressions when evaluating them.
+                // This allows to evaluate nearly all instructions at compile time.
+                const_eval: RunState {
+                    thread_info: ti.clone(),
+                    cr: Default::default(),
+                    parked: Default::default(),
+                    global_regs: [0; REG_COUNT],
+                    ext_data: Default::default(),
+                    cr_deadline: None
+                },
+                const_eval_ti: ti.clone(),
+                parsing_expr: false
+            }),
+        };
 
         for (sample, expected) in samples {
-            let pcx = ParserContext {
-                parsers,
-                state: Default::default(),
-            };
+            pcx.state.borrow_mut().reset();
 
             println!("Parse: {}", sample);
 
@@ -587,10 +621,7 @@ mod test {
             assert_eq!(expected, exported);
 
             println!(" - 2nd cycle");
-            let pcx = ParserContext {
-                parsers,
-                state: Default::default(),
-            };
+            pcx.state.borrow_mut().reset();
 
             /* second cycle, nothing should change */
             let s = sexp::parse(&format!("({})", exported))
diff --git a/crsn/src/runtime/run_thread.rs b/crsn/src/runtime/run_thread.rs
index fb58990..632f403 100644
--- a/crsn/src/runtime/run_thread.rs
+++ b/crsn/src/runtime/run_thread.rs
@@ -126,7 +126,7 @@ impl RunThread {
                             'find: for (n, th) in self.state.parked.iter_mut().enumerate() {
                                 if th.handle == handle {
                                     if let CoroutineState::Finished(_) = &th.cr_state {
-                                        let mut crs = mem::replace(&mut th.cr_state, CoroutineState::Ready);
+                                        let crs = mem::replace(&mut th.cr_state, CoroutineState::Ready);
                                         self.state.parked.remove(n); // delete it
                                         found = true;
 
diff --git a/crsn/src/runtime/run_thread/state.rs b/crsn/src/runtime/run_thread/state.rs
index 5b3ffc2..0e0341f 100644
--- a/crsn/src/runtime/run_thread/state.rs
+++ b/crsn/src/runtime/run_thread/state.rs
@@ -72,7 +72,7 @@ impl Default for CoroutineState {
 
 impl RunState {
     /// Clear everything. Caution: when done at runtime, this effectively reboots the thread
-    pub fn clear_all(&mut self) {
+    pub fn reset(&mut self) {
         self.cr = Default::default();
         self.parked = Default::default();
         self.global_regs = Default::default();