Merge pull request #262 from HigherOrderCO/bug/sc-510/unused-definition-warning-triggered-on-matched

[sc-510] Unused definition warning triggered on matched constructors when scott encoding is used

src/term/transform/definition_pruning.rs

@@ -38,6 +38,14 @@ impl Ctx<'_> {
       self.book.find_used_definitions(&def.rule().body, Used::Main, &mut used, adt_encoding);
     }
 
+    if let AdtEncoding::Scott = adt_encoding {
+      for (def_name, def) in &self.book.defs {
+        if !def.builtin && self.book.ctrs.get(def_name).is_some() {
+          used.insert(def_name.clone(), Used::Adt);
+        }
+      }
+    }
+
     // Even if we don't prune all the defs, we need check what built-ins are accessible through user code
     if !prune_all {
       for (def_name, def) in &self.book.defs {

tests/golden_tests.rs

@@ -451,3 +451,16 @@ fn examples() -> Result<(), Diagnostics> {
 
   Ok(())
 }
+
+#[test]
+fn scott_triggers_unused() {
+  run_golden_test_dir(function_name!(), &|code, path| {
+    let mut book = do_parse_book(code, path)?;
+    let mut opts = CompileOpts::default_strict();
+    opts.adt_encoding = AdtEncoding::Scott;
+    let diagnostics_cfg =
+      DiagnosticsConfig { unused_definition: Severity::Error, ..DiagnosticsConfig::default_strict() };
+    let res = compile_book(&mut book, opts, diagnostics_cfg, None)?;
+    Ok(format!("{}{}", res.diagnostics, res.core_book))
+  })
+}

tests/golden_tests/scott_triggers_unused/test.hvm

@@ -0,0 +1,13 @@
+// The test below should not trigger this warning:
+//
+// In definition 'f':
+//   Definition is unused.
+// In definition 't':
+//   Definition is unused.
+//
+// This was happening because the prune algorithm was just collecting constructors
+// by searching for tags.
+
+data bool = t | f
+
+main = @b match b { t: 0; f: 1}

tests/snapshots/scott_triggers_unused__test.hvm.snap

@@ -0,0 +1,9 @@
+---
+source: tests/golden_tests.rs
+input_file: tests/golden_tests/scott_triggers_unused/test.hvm
+---
+@f = (* (a a))
+
+@main = ((#0 (#1 a)) a)
+
+@t = (a (* a))