message: Add parse test for import syntax
diff: @@ -119,6 +119,50 @@ mod tests {
  use super::*;
  + #[test]
  + fn imports() {
  + let src = r#"
  + prims = import "prims.pi";
  + prelude = import "prelude.pi";
  + "#;
  + let mut codemap = CodeMap::new();
  + let filemap = codemap.add_filemap(FileName::virtual_("test"), src.into());
  +
  + let parse_result = module(&filemap);
  +
  + assert_eq!(
  + parse_result,
  + (
  + concrete::Module::Valid {
  + items: vec![
  + concrete::Item::Definition {
  + name: (ByteIndex(14), "prims".to_owned()),
  + params: vec![],
  + return_ann: None,
  + body: concrete::Term::Import(
  + ByteSpan::new(ByteIndex(22), ByteIndex(39)),
  + ByteSpan::new(ByteIndex(29), ByteIndex(39)),
  + "prims.pi".to_owned(),
  + ),
  + },
  + concrete::Item::Definition {
  + name: (ByteIndex(53), "prelude".to_owned()),
  + params: vec![],
  + return_ann: None,
  + body: concrete::Term::Import(
  + ByteSpan::new(ByteIndex(63), ByteIndex(82)),
  + ByteSpan::new(ByteIndex(70), ByteIndex(82)),
  + "prelude.pi".to_owned(),
  + ),
  + }
  + ],
  + },
  + vec!["prims.pi".to_owned(), "prelude.pi".to_owned()],
  + vec![],
  + )
  + );
  + }
  +
  #[test]
  fn pi_bad_ident() {
  let src = "((x : Type) : Type) -> Type";
  