dsl: extract dsl_error; ParseError -> DslError

dsl/src/dsl_error.rs

@@ -0,0 +1,16 @@
+use crate::*;
+
+pub type DslResult<T> = Result<T, DslError>;
+
+#[derive(Error, Debug, Copy, Clone, PartialEq)] pub enum DslError {
+    #[error("parse failed: not implemented")]
+    Unimplemented,
+    #[error("parse failed: empty")]
+    Empty,
+    #[error("parse failed: incomplete")]
+    Incomplete,
+    #[error("parse failed: unexpected character '{0}'")]
+    Unexpected(char),
+    #[error("parse failed: error #{0}")]
+    Code(u8),
+}

dsl/src/dsl_parse.rs

@@ -1,20 +1,5 @@
 use crate::*;
 
-pub type ParseResult<T> = Result<T, ParseError>;
-
-#[derive(Error, Debug, Copy, Clone, PartialEq)] pub enum ParseError {
-    #[error("parse failed: not implemented")]
-    Unimplemented,
-    #[error("parse failed: empty")]
-    Empty,
-    #[error("parse failed: incomplete")]
-    Incomplete,
-    #[error("parse failed: unexpected character '{0}'")]
-    Unexpected(char),
-    #[error("parse failed: error #{0}")]
-    Code(u8),
-}
-
 /// Implement the const iterator pattern.
 #[macro_export] macro_rules! const_iter {
     ($(<$l:lifetime>)?|$self:ident: $Struct:ty| => $Item:ty => $expr:expr) => {
@@ -170,7 +155,7 @@ pub const fn peek_src <'a> (source: &'a str) -> Option<Token<'a>> {
     }
 }
 
-pub const fn to_number (digits: &str) -> Result<usize, ParseError> {
+pub const fn to_number (digits: &str) -> DslResult<usize> {
     let mut value = 0;
     iterate!(char_indices(digits) => (_, c) => match to_digit(c) {
         Ok(digit) => value = 10 * value + digit,
@@ -179,7 +164,7 @@ pub const fn to_number (digits: &str) -> Result<usize, ParseError> {
     Ok(value)
 }
 
-pub const fn to_digit (c: char) -> Result<usize, ParseError> {
+pub const fn to_digit (c: char) -> DslResult<usize> {
     Ok(match c {
         '0' => 0, '1' => 1, '2' => 2, '3' => 3, '4' => 4,
         '5' => 5, '6' => 6, '7' => 7, '8' => 8, '9' => 9,
@@ -196,7 +181,7 @@ pub const fn to_digit (c: char) -> Result<usize, ParseError> {
 
 #[derive(Debug, Copy, Clone, Default, PartialEq)] pub enum Value<'source> {
     #[default] Nil,
-    Err(ParseError),
+    Err(DslError),
     Num(usize),
     Sym(&'source str),
     Key(&'source str),
@@ -228,7 +213,7 @@ impl<'source> Token<'source> {
     pub const fn value (&self) -> Value {
         self.value
     }
-    pub const fn error (self, error: ParseError) -> Self {
+    pub const fn error (self, error: DslError) -> Self {
         Self { value: Value::Err(error), ..self }
     }
     pub const fn grow (self) -> Self {

dsl/src/dsl_provide.rs

@@ -1,10 +1,21 @@
 use crate::*;
 
 /// Map EDN tokens to parameters of a given type for a given context
+/// TODO: Replace both [Context] and [TryFromDsl] with this trait
+/// which returns a [Result].
 pub trait Dsl<U>: Sized {
     fn take <'state, 'source> (_: &'state Self, _: &mut TokenIter<'source>) -> Perhaps<U> {
         Ok(None)
     }
+    fn take_or_fail <'state, 'source> (
+        state: &'state Self, iter: &mut TokenIter<'source>
+    ) -> Usually<U> {
+        if let Some(value) = Self::take(state, iter)? {
+            Ok(value)
+        } else {
+            Result::Err("not found".into()) // TODO add info and error type
+        }
+    }
 }
 
 /// Map EDN tokens to parameters of a given type for a given context

dsl/src/lib.rs

@@ -43,8 +43,9 @@ pub(crate) use konst::iter::{ConstIntoIter, IsIteratorKind};
 pub(crate) use konst::string::{split_at, str_range, char_indices};
 pub(crate) use thiserror::Error;
 pub(crate) use self::Value::*;
-pub(crate) use self::ParseError::*;
+pub(crate) use self::DslError::*;
 
+mod dsl_error;   pub use self::dsl_error::*;
 mod dsl_parse;   pub use self::dsl_parse::*;
 mod dsl_provide; pub use self::dsl_provide::*;
 
@@ -148,7 +149,7 @@ mod dsl_provide; pub use self::dsl_provide::*;
     Ok(())
 }
 
-//#[cfg(test)] #[test] fn test_examples () -> Result<(), ParseError> {
+//#[cfg(test)] #[test] fn test_examples () -> Result<(), DslError> {
     //// Let's pretend to render some view.
     //let source = include_str!("../../tek/src/view_arranger.edn");
     //// The token iterator allows you to get the tokens represented by the source text.