Revert "Use strings for errors."

This reverts commit 7b87d7185fc93b92606fcacbc1ea3d7a8e02cb20.

It was an interesting experiment, but String seems to be worse than
Box<dyn Error> in every way.

1 files changed, 23 insertions, 23 deletions

diff --git a/bytecode/src/encoding.rs b/bytecode/src/encoding.rs
index 81cb29f..80fcc58 100644
--- a/bytecode/src/encoding.rs
+++ b/bytecode/src/encoding.rs
@@ -1,5 +1,6 @@
 use crate::heap;
 use crate::value::Value;
+use std::error::Error;
 
 #[derive(Debug, Clone, Copy)]
 pub enum Arg {
@@ -114,30 +115,30 @@ impl Reader<'_> {
         self.n += size;
     }
 
-    fn parse_byte(&mut self) -> Result<u8, String> {
+    fn parse_byte(&mut self) -> Result<u8, Box<dyn Error>> {
         if self.data.is_empty() {
-            return Err(String::from("read byte: no data"));
+            return Err(Box::from("read byte: no data"));
         }
         let res = self.data[0];
         self.advance(1);
         Ok(res)
     }
 
-    fn parse_local(&mut self) -> Result<u8, String> {
+    fn parse_local(&mut self) -> Result<u8, Box<dyn Error>> {
         if self.data.is_empty() {
-            return Err(String::from("local: no data"));
+            return Err(Box::from("local: no data"));
         }
         let res = self.data[0];
         if usize::from(res) >= heap::NUM_LOCALS {
-            return Err(format!("invalid local (out of range): {}", res));
+            return Err(Box::from(format!("invalid local (out of range): {}", res)));
         }
         self.advance(1);
         Ok(res)
     }
 
-    fn parse_value(&mut self) -> Result<Value, String> {
+    fn parse_value(&mut self) -> Result<Value, Box<dyn Error>> {
         if self.data.len() < 8 {
-            return Err(String::from("value: no data"));
+            return Err(Box::from("value: no data"));
         }
         let mut res = [0; 8];
         res.copy_from_slice(&self.data[..8]);
@@ -145,17 +146,7 @@ impl Reader<'_> {
         Ok(Value(u64::from_le_bytes(res)))
     }
 
-    fn parse_offset(&mut self) -> Result<usize, String> {
-        let Some(ioffset) = self.parse_value()?.to_int() else {
-            return Err(String::from("invalid offset"));
-        };
-        let Ok(offset) = usize::try_from(ioffset) else {
-            return Err(String::from("invalid offset"));
-        };
-        Ok(offset)
-    }
-
-    fn parse_arg(&mut self, is_const: bool) -> Result<Arg, String> {
+    fn parse_arg(&mut self, is_const: bool) -> Result<Arg, Box<dyn Error>> {
         if is_const {
             Ok(Arg::Const(self.parse_value()?))
         } else {
@@ -165,7 +156,7 @@ impl Reader<'_> {
 }
 
 impl Op {
-    pub fn parse(data: &[u8]) -> Result<(usize, Op), String> {
+    pub fn parse(data: &[u8]) -> Result<(usize, Op), Box<dyn Error>> {
         let mut r = Reader { data, n: 0 };
         let code_byte = r.parse_byte()?;
         let code = code_byte >> 2;
@@ -180,14 +171,20 @@ impl Op {
             }
             2 => Op::Call,
             3 => {
-                let offset = r.parse_offset()?;
+                let Some(ioffset) = r.parse_value()?.to_int() else {
+                    return Err(Box::from("invalid offset"));
+                };
+                let offset = usize::try_from(ioffset)?;
                 let ptr = r.parse_local()?;
                 let val = r.parse_arg(arg1_const)?;
                 Op::Poke(Poke { offset, ptr, val })
             }
             4 => {
                 let out = r.parse_local()?;
-                let offset = r.parse_offset()?;
+                let Some(ioffset) = r.parse_value()?.to_int() else {
+                    return Err(Box::from("invalid offset"));
+                };
+                let offset = usize::try_from(ioffset)?;
                 let val = r.parse_arg(arg1_const)?;
                 Op::Peek(Peek { out, offset, val })
             }
@@ -238,11 +235,14 @@ impl Op {
             }
             13 => {
                 let test = r.parse_arg(arg1_const)?;
-                let target = r.parse_offset()?;
+                let Some(itarget) = r.parse_value()?.to_int() else {
+                    return Err(Box::from("invalid target"));
+                };
+                let target = usize::try_from(itarget)?;
                 Op::If(If { test, target })
             }
             _ => {
-                return Err(format!("invalid code {}", code));
+                return Err(Box::from(format!("invalid code {}", code)));
             }
         };