[meta] Add the ability to bind any type to an instruction;

cranelift/codegen/meta/src/cdsl/ast.rs

@@ -376,11 +376,17 @@ pub struct Apply {
 
 impl Apply {
     pub fn new(target: InstSpec, args: Vec<Expr>) -> Self {
-        let (inst, value_types) = match target.into() {
+        let (inst, value_types) = match target {
             InstSpec::Inst(inst) => (inst, Vec::new()),
             InstSpec::Bound(bound_inst) => (bound_inst.inst, bound_inst.value_types),
         };
 
+        // Apply should only operate on concrete value types, not "any".
+        let value_types = value_types
+            .into_iter()
+            .map(|vt| vt.expect("shouldn't be Any"))
+            .collect();
+
         // Basic check on number of arguments.
         assert!(
             inst.operands_in.len() == args.len(),