Implement core lexer and parser

crates/decodal-core/src/diagnostic.rs

@@ -0,0 +1,41 @@
+use alloc::string::String;
+
+use crate::span::Span;
+
+pub type Result<T> = core::result::Result<T, Diagnostic>;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Diagnostic {
+    pub kind: DiagnosticKind,
+    pub span: Span,
+    pub message: String,
+}
+
+impl Diagnostic {
+    pub fn new(kind: DiagnosticKind, span: Span, message: impl Into<String>) -> Self {
+        Self {
+            kind,
+            span,
+            message: message.into(),
+        }
+    }
+
+    pub fn syntax(span: Span, message: impl Into<String>) -> Self {
+        Self::new(DiagnosticKind::Syntax, span, message)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum DiagnosticKind {
+    Syntax,
+    UnresolvedIdentifier,
+    TypeMismatch,
+    ConstraintViolation,
+    Conflict,
+    DefaultConflict,
+    Cycle,
+    Import,
+    MatchFailure,
+    Materialize,
+    UnsupportedFeature,
+}