Improved SSA and added unused value checks

src/core/CheckDeadCode.go

@@ -0,0 +1,16 @@
+package core
+
+import (
+	"git.urbach.dev/cli/q/src/errors"
+)
+
+// CheckDeadCode checks for dead values.
+func (f *Function) CheckDeadCode() error {
+	for instr := range f.Values {
+		if instr.IsConst() && instr.Alive() == 0 {
+			return errors.New(&UnusedValue{Value: instr.String()}, f.File, instr.Token().Position)
+		}
+	}
+
+	return nil
+}