implement better checking and errors

src/syntax/error.rs

@@ -0,0 +1,48 @@
+use codespan_reporting::diagnostic::{Diagnostic, Label};
+
+pub type FileId = usize;
+
+/// The enum representing a syntax error, used for error reporting
+#[derive(Debug, Clone)]
+pub enum SyntaxError {
+    /// This variant indicates a token that the Lexer didn't recognize
+    InvalidToken(Vec<(FileId, logos::Span)>),
+    /// `MissingStreamer` means, that the pipeline starts with a Pipe (`|`), so it has no streamer as input in front of it.
+    MissingStreamer(Vec<(FileId, logos::Span)>),
+    /// `MissingSink` means, that the pipeline ends with a Pipe (`|`), meaning that the output can't go anywhere
+    MissingSink,
+    /// This indicates a missing filter somewhere in the pipeline, meaning that there's 2 pipes after one another
+    MissingFilter,
+    /// A literal cannot be a sink
+    LiteralAsSink,
+    /// A literal can't be a filter either
+    LiteralAsFilter,
+    /// A literal acting as streamer cannot take arguments
+    LiteralWithArgs,
+}
+
+impl SyntaxError {
+    pub fn to_diagnostic(&self) -> Diagnostic<usize> {
+        match self {
+            Self::InvalidToken(errs) => Diagnostic::error()
+                .with_message("failed to parse invalid tokens")
+                .with_labels(
+                    errs.into_iter()
+                        .map(|(file_id, span)| {
+                            Label::primary(*file_id, span.clone()).with_message("invalid token")
+                        })
+                        .collect(),
+                ),
+            Self::MissingStreamer(locs) => Diagnostic::error()
+                .with_message("pipelines must always start with a streamer")
+                .with_labels(
+                    locs.into_iter()
+                        .map(|(file_id, span)| {
+                            Label::primary(*file_id, span.clone()).with_message("missing streamer")
+                        })
+                        .collect(),
+                ),
+            _ => todo!(),
+        }
+    }
+}