Error Messaging Redesign

This commit contains the following:

* New data types to support full tracebacks
* New traceback data type used across stl and ast
* Updates to tests
* fixes for error messaging in sym and some stl functions

src/stl/boolean.rs

@@ -15,6 +15,7 @@
  */
 
 use crate::segment::{Ctr, Seg};
+use crate::error::{Traceback, start_trace};
 use crate::sym::{SymTable, ValueType};
 
 pub const AND_DOCSTRING: &str =
@@ -22,20 +23,21 @@ pub const AND_DOCSTRING: &str =
 starts with arg1 AND arg2, and then calculates prev_result AND next_arg.
 returns final result.";
 
-pub fn and_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
+pub fn and_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
     let mut type_error = false;
+    let mut cursor = 0;
     let result = ast.circuit(&mut |arg: &Ctr| -> bool {
         if let Ctr::Bool(b) = *arg {
+            cursor += 1;
             b
         } else {
-            eprintln!("{} is not a boolean", arg);
             type_error = true;
             false
         }
     });
 
     if type_error {
-        Err("all arguments to and must evaluate to boolean".to_string())
+        Err(start_trace(("and", format!("input {} not a boolean", cursor)).into()))
     } else {
         Ok(Ctr::Bool(result))
     }
@@ -46,20 +48,21 @@ pub const OR_DOCSTRING: &str =
 starts with arg1 OR arg2, and then calculates prev_result OR next_arg.
 returns final result.";
 
-pub fn or_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
+pub fn or_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
     let mut result = false;
+    let mut cursor = 0;
     let correct_types = ast.circuit(&mut |arg: &Ctr| -> bool {
         if let Ctr::Bool(b) = *arg {
+            cursor += 1;
             result = result || b;
             true
         } else {
-            eprintln!("{} is not a boolean", arg);
             false
         }
     });
 
     if !correct_types {
-        Err("all arguments to 'or' must evaluate to boolean".to_string())
+        Err(start_trace(("or", format!("input {} not a boolean", cursor)).into()))
     } else {
         Ok(Ctr::Bool(result))
     }
@@ -68,11 +71,11 @@ pub fn or_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
 pub const NOT_DOCSTRING: &str = "takes a single argument (expects a boolean).
 returns false if arg is true or true if arg is false.";
 
-pub fn not_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
+pub fn not_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
     if let Ctr::Bool(b) = *ast.car {
         Ok(Ctr::Bool(!b))
     } else {
-        Err("impossible state: non bool given to not".to_string())
+        Err(start_trace(("not", "input is not a bool").into()))
     }
 }
 
@@ -80,7 +83,7 @@ pub const ISEQ_DOCSTRING: &str = "traverses a list of N arguments.
 returns true if all arguments hold the same value.
 NOTE: 1 and 1.0 are the same, but '1' 'one' or one (symbol) aren't";
 
-pub fn iseq_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
+pub fn iseq_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
     let head_ctr_ref = &*ast.car;
     Ok(Ctr::Bool(
         ast.circuit(&mut |arg: &Ctr| -> bool { arg == head_ctr_ref }),
@@ -91,12 +94,12 @@ pub const TOGGLE_DOCSTRING: &str = "switches a boolean symbol between true or fa
 Takes a single argument (a symbol). Looks it up in the variable table.
 Either sets the symbol to true if it is currently false, or vice versa.";
 
-pub fn toggle_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, String> {
+pub fn toggle_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback> {
     let var_name: String;
     if let Ctr::Symbol(ref s) = *ast.car {
         var_name = s.clone();
     } else {
-        return Err("argument to toggle should be a symbol".to_string());
+        return Err(start_trace(("toggle", "input must be a symbol").into()));
     }
 
     let mut sym = syms
@@ -107,11 +110,11 @@ pub fn toggle_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, String> {
             sym.value = ValueType::VarForm(Box::new(Ctr::Bool(!b)));
         } else {
             syms.insert(var_name, sym);
-            return Err("can only toggle a boolean".to_string());
+            return Err(start_trace(("toggle", "can only toggle a boolean").into()));
         }
     } else {
         syms.insert(var_name, sym);
-        return Err("cannot toggle a function".to_string());
+        return Err(start_trace(("toggle", "cannot toggle a function").into()));
     }
 
     syms.insert(var_name, sym);
@@ -124,7 +127,7 @@ attempts to cast argument to a bool.
 Strings will cast to a bool if they are 'true' or 'false'.
 Integers and Floats will cast to true if they are 0 and false otherwise.";
 
-pub fn boolcast_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
+pub fn boolcast_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
     match &*ast.car {
         Ctr::Bool(_) => Ok(*ast.car.clone()),
         Ctr::String(s) => {
@@ -133,12 +136,12 @@ pub fn boolcast_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String>
             } else if s == "false" {
                 Ok(Ctr::Bool(false))
             } else {
-                Err("string cannot be parsed as a bool".to_string())
+                Err(start_trace(("bool", "string cannot be parsed as a bool").into()))
             }
         },
         Ctr::Integer(i) => Ok(Ctr::Bool(*i == 0)),
         Ctr::Float(f) => Ok(Ctr::Bool(*f == 0.0)),
-        _ => Err(format!("cannot convert a {} to a boolean",
-                         ast.car.to_type())),
+        _ => Err(start_trace(("bool", format!("cannot convert a {} to a boolean",
+                         ast.car.to_type())).into())),
     }
 }