Add regresstion test for type path panic (tweag#1021)

tests/integration/contracts_fail.rs

@@ -2,7 +2,7 @@ use assert_matches::assert_matches;
 use codespan::Files;
 use nickel_lang::error::{Error, EvalError, ToDiagnostic};
 
-use nickel_lang_utilities::eval;
+use nickel_lang_utilities::{eval, program_from_expr};
 
 macro_rules! assert_raise_blame {
     ($term:expr) => {{
@@ -285,3 +285,23 @@ fn enum_complex() {
     )
     .unwrap_err();
 }
+
+// Regression test for https://github.com/tweag/nickel/issues/1021
+#[test]
+fn type_path_with_aliases() {
+    #[track_caller]
+    fn assert_blame_dont_panic(expr: &str) {
+        let mut p = program_from_expr(expr);
+        let result = p.eval();
+        assert_matches!(result, Err(Error::EvalError(EvalError::BlameError(..))));
+        // Check that the diagnostic is correctly produced
+        p.report(result.unwrap_err());
+    }
+
+    assert_blame_dont_panic("let Foo = Array Num in %force% ([\"a\"] | Foo)");
+    assert_blame_dont_panic("let Foo = Num -> Num in ((fun x => \"a\") | Foo) 0");
+    assert_blame_dont_panic("let Foo = Num -> Num in ((fun x => x) | Foo) \"a\"");
+    assert_blame_dont_panic(
+        "let Foo = {foo: Num} in %force% (((fun x => {foo = \"a\"}) | Dyn -> Foo) null)",
+    );
+}

utilities/src/lib.rs

@@ -19,9 +19,13 @@ use std::{io::Cursor, path::PathBuf};
 pub type EC = CBNCache;
 pub type TestProgram = Program<EC>;
 
+/// Create a program from a Nickel expression provided as a string.
+pub fn program_from_expr(s: impl std::string::ToString) -> Program<EC> {
+    Program::<EC>::new_from_source(Cursor::new(s.to_string()), "test").unwrap()
+}
+
 pub fn eval(s: impl std::string::ToString) -> Result<Term, Error> {
-    let mut p = Program::<EC>::new_from_source(Cursor::new(s.to_string()), "test").unwrap();
-    p.eval().map(Term::from)
+    program_from_expr(s).eval().map(Term::from)
 }
 
 pub fn eval_file(f: &str) -> Result<Term, Error> {