All symbols to start a custom syntax.

CHANGELOG.md

@@ -12,6 +12,7 @@ Bug fixes
 * Syntax such as `foo.bar::baz` no longer panics, but returns a proper parse error.
 * `x += y` where `x` and `y` are `char` now works correctly.
 * Expressions such as `!inside` now parses correctly instead of as `!in` followed by `side`.
+* Custom syntax starting with symbols now works correctly and no longer raises a parse error.
 
 Potentially breaking changes
 ----------------------------

src/api/custom_syntax.rs

@@ -255,7 +255,8 @@ impl Engine {
                 // Markers not in first position
                 #[cfg(not(feature = "no_float"))]
                 CUSTOM_SYNTAX_MARKER_FLOAT if !segments.is_empty() => s.into(),
-                // Standard or reserved keyword/symbol not in first position
+
+                // Keyword/symbol not in first position
                 _ if !segments.is_empty() && token.is_some() => {
                     // Make it a custom keyword/symbol if it is disabled or reserved
                     if (self
@@ -274,6 +275,7 @@ impl Engine {
                     }
                     s.into()
                 }
+
                 // Standard keyword in first position but not disabled
                 _ if segments.is_empty()
                     && token.as_ref().map_or(false, Token::is_standard_keyword)
@@ -291,8 +293,11 @@ impl Engine {
                     )
                     .into_err(Position::NONE));
                 }
-                // Identifier in first position
-                _ if segments.is_empty() && is_valid_identifier(s) => {
+
+                // Identifier or symbol in first position
+                _ if segments.is_empty()
+                    && (is_valid_identifier(s) || is_reserved_keyword_or_symbol(s)) =>
+                {
                     // Make it a custom keyword/symbol if it is disabled or reserved
                     if self
                         .disabled_symbols
@@ -310,6 +315,7 @@ impl Engine {
                     }
                     s.into()
                 }
+
                 // Anything else is an error
                 _ => {
                     return Err(LexError::ImproperSymbol(
@@ -326,23 +332,20 @@ impl Engine {
             segments.push(seg);
         }
 
-        // If the syntax has no symbols, just ignore the registration
+        // If the syntax has nothing, just ignore the registration
         if segments.is_empty() {
             return Ok(self);
         }
 
-        // The first keyword is the discriminator
+        // The first keyword/symbol is the discriminator
         let key = segments[0].clone();
 
         self.register_custom_syntax_with_state_raw(
             key,
             // Construct the parsing function
-            move |stream, _, _| {
-                if stream.len() >= segments.len() {
-                    Ok(None)
-                } else {
-                    Ok(Some(segments[stream.len()].clone()))
-                }
+            move |stream, _, _| match stream.len() {
+                len if len >= segments.len() => Ok(None),
+                len => Ok(Some(segments[len].clone())),
             },
             scope_may_be_changed,
             move |context, expressions, _| func(context, expressions),

src/parser.rs

@@ -3792,7 +3792,7 @@ impl Engine {
                     (.., pos) => {
                         return Err(PERR::MissingToken(
                             Token::Pipe.into(),
-                            "to close the parameters list of anonymous function".into(),
+                            "to close the parameters list of anonymous function or closure".into(),
                         )
                         .into_err(pos))
                     }

src/tokenizer.rs

@@ -2066,7 +2066,7 @@ pub const fn is_id_continue(x: char) -> bool {
     x.is_ascii_alphanumeric() || x == '_'
 }
 
-/// Is a piece of syntax a reserved keyword or symbol?
+/// Is a piece of syntax a reserved keyword or reserved symbol?
 #[must_use]
 pub fn is_reserved_keyword_or_symbol(syntax: &str) -> bool {
     match syntax {

tests/custom_syntax.rs

@@ -251,6 +251,62 @@ fn test_custom_syntax() -> Result<(), Box<EvalAltResult>> {
     Ok(())
 }
 
+#[test]
+fn test_custom_syntax_matrix() -> Result<(), Box<EvalAltResult>> {
+    let mut engine = Engine::new();
+
+    engine.disable_symbol("|");
+
+    engine.register_custom_syntax(
+        [
+            "@", //
+            "|", "$expr$", "$expr$", "$expr$", "|", //
+            "|", "$expr$", "$expr$", "$expr$", "|", //
+            "|", "$expr$", "$expr$", "$expr$", "|",
+        ],
+        false,
+        |context, inputs| {
+            let mut values = [[0; 3]; 3];
+
+            for y in 0..3 {
+                for x in 0..3 {
+                    let offset = y * 3 + x;
+
+                    match context.eval_expression_tree(&inputs[offset])?.as_int() {
+                        Ok(v) => values[y][x] = v,
+                        Err(typ) => {
+                            return Err(Box::new(EvalAltResult::ErrorMismatchDataType(
+                                "integer".to_string(),
+                                typ.to_string(),
+                                inputs[offset].position(),
+                            )))
+                        }
+                    }
+                }
+            }
+
+            Ok(Dynamic::from(values))
+        },
+    )?;
+
+    let r = engine.eval::<[[INT; 3]; 3]>(
+        "
+            let a = 42;
+            let b = 123;
+            let c = 1;
+            let d = 99;
+
+            @|  a   b   0  |
+             | -b   a   0  |
+             |  0   0  c*d |
+        ",
+    )?;
+
+    assert_eq!(r, [[42, 123, 0], [-123, 42, 0], [0, 0, 99]]);
+
+    Ok(())
+}
+
 #[test]
 fn test_custom_syntax_raw() -> Result<(), Box<EvalAltResult>> {
     let mut engine = Engine::new();