implement better checking and errors

src/syntax/check.rs

@@ -0,0 +1,34 @@
+use super::{
+    error::{FileId, SyntaxError},
+    PipelineElement, PipelineElementKind,
+};
+
+pub fn check(
+    syntax: Vec<PipelineElement>,
+    raw_source: &str,
+    file_id: FileId,
+) -> Result<Vec<PipelineElement>, Vec<SyntaxError>> {
+    let mut errs = Vec::new();
+
+    if let Err(e_span) = check_missing_streamer(&syntax) {
+        errs.push(SyntaxError::MissingStreamer(vec![(file_id, e_span)]));
+    }
+
+    if errs.is_empty() {
+        Ok(syntax)
+    } else {
+        Err(errs)
+    }
+}
+
+fn check_missing_streamer(syntax: &Vec<PipelineElement>) -> Result<(), logos::Span> {
+    if let Some(&PipelineElement {
+        kind: PipelineElementKind::Pipe,
+        ref span,
+    }) = syntax.first()
+    {
+        Err(span.clone())
+    } else {
+        Ok(())
+    }
+}