Merge pull request #133 from HigherOrderCO/feature/sc-359/don-t-allow-main-to-be-called-by-any-functions

[sc-359] Don't allow main to be called by any functions

src/lib.rs

@@ -42,7 +42,7 @@ pub fn desugar_book(book: &mut Book, opt_level: OptimizationLevel) -> Result<Def
   book.encode_strs()?;
   book.encode_lists()?;
   book.generate_scott_adts();
-  book.resolve_refs();
+  book.resolve_refs()?;
   encode_pattern_matching(book)?;
   book.normalize_native_matches()?;
   book.check_unbound_vars()?;

src/term/transform/resolve_refs.rs

@@ -6,52 +6,57 @@ impl Book {
   /// Decides if names inside a term belong to a Var or to a Ref.
   /// Precondition: Refs are encoded as vars.
   /// Postcondition: Refs are encoded as refs, with the correct def id.
-  pub fn resolve_refs(&mut self) {
+  pub fn resolve_refs(&mut self) -> Result<(), String> {
     for def in self.defs.values_mut() {
       for rule in def.rules.iter_mut() {
-        rule.body.resolve_refs(&self.def_names);
+        rule.body.resolve_refs(&self.def_names)?;
       }
     }
+    Ok(())
   }
 }
 
 impl Term {
-  pub fn resolve_refs(&mut self, def_names: &DefNames) {
+  pub fn resolve_refs(&mut self, def_names: &DefNames) -> Result<(), String> {
     resolve_refs(self, def_names, &mut HashMap::new())
   }
 }
 
-fn resolve_refs(term: &mut Term, def_names: &DefNames, scope: &mut HashMap<Name, usize>) {
+fn resolve_refs(
+  term: &mut Term,
+  def_names: &DefNames,
+  scope: &mut HashMap<Name, usize>,
+) -> Result<(), String> {
   match term {
     Term::Lam { nam, bod, .. } => {
       push_scope(nam.clone(), scope);
-      resolve_refs(bod, def_names, scope);
+      resolve_refs(bod, def_names, scope)?;
       pop_scope(nam.clone(), scope);
     }
     Term::Let { pat: Pattern::Var(nam), val, nxt } => {
-      resolve_refs(val, def_names, scope);
+      resolve_refs(val, def_names, scope)?;
       push_scope(nam.clone(), scope);
-      resolve_refs(nxt, def_names, scope);
+      resolve_refs(nxt, def_names, scope)?;
       pop_scope(nam.clone(), scope);
     }
     Term::Let { pat, val, nxt } => {
-      resolve_refs(val, def_names, scope);
+      resolve_refs(val, def_names, scope)?;
 
       for nam in pat.names() {
         push_scope(Some(nam.clone()), scope)
       }
 
-      resolve_refs(nxt, def_names, scope);
+      resolve_refs(nxt, def_names, scope)?;
 
       for nam in pat.names() {
         pop_scope(Some(nam.clone()), scope)
       }
     }
     Term::Dup { tag: _, fst, snd, val, nxt } => {
-      resolve_refs(val, def_names, scope);
+      resolve_refs(val, def_names, scope)?;
       push_scope(fst.clone(), scope);
       push_scope(snd.clone(), scope);
-      resolve_refs(nxt, def_names, scope);
+      resolve_refs(nxt, def_names, scope)?;
       pop_scope(fst.clone(), scope);
       pop_scope(snd.clone(), scope);
     }
@@ -59,27 +64,31 @@ fn resolve_refs(term: &mut Term, def_names: &DefNames, scope: &mut HashMap<Name,
     // If variable not defined, we check if it's a ref and swap if it is.
     Term::Var { nam } => {
       if is_var_in_scope(nam.clone(), scope) {
+        if matches!(nam.0.as_ref(), DefNames::ENTRY_POINT | DefNames::HVM1_ENTRY_POINT) {
+          return Err("Main definition can't be referenced inside the program".to_string());
+        }
+
         if let Some(def_id) = def_names.def_id(nam) {
           *term = Term::Ref { def_id };
         }
       }
     }
-    Term::Chn { bod, .. } => resolve_refs(bod, def_names, scope),
+    Term::Chn { bod, .. } => resolve_refs(bod, def_names, scope)?,
     Term::App { fun: fst, arg: snd, .. }
     | Term::Sup { fst, snd, .. }
     | Term::Tup { fst, snd }
     | Term::Opx { fst, snd, .. } => {
-      resolve_refs(fst, def_names, scope);
-      resolve_refs(snd, def_names, scope);
+      resolve_refs(fst, def_names, scope)?;
+      resolve_refs(snd, def_names, scope)?;
     }
     Term::Match { scrutinee, arms } => {
-      resolve_refs(scrutinee, def_names, scope);
+      resolve_refs(scrutinee, def_names, scope)?;
       for (pat, term) in arms {
         if let Pattern::Num(MatchNum::Succ(Some(nam))) = pat {
           push_scope(nam.clone(), scope)
         }
 
-        resolve_refs(term, def_names, scope);
+        resolve_refs(term, def_names, scope)?;
 
         if let Pattern::Num(MatchNum::Succ(Some(nam))) = pat {
           pop_scope(nam.clone(), scope)
@@ -89,6 +98,8 @@ fn resolve_refs(term: &mut Term, def_names: &DefNames, scope: &mut HashMap<Name,
     Term::List { .. } => unreachable!("Should have been desugared already"),
     Term::Lnk { .. } | Term::Ref { .. } | Term::Num { .. } | Term::Str { .. } | Term::Era => (),
   }
+
+  Ok(())
 }
 
 fn push_scope(name: Option<Name>, scope: &mut HashMap<Name, usize>) {

src/term/transform/simplify_ref_to_ref.rs

@@ -15,10 +15,10 @@ impl Book {
       let mut ref_id = def_id;
       let mut is_ref_to_ref = false;
       while let Term::Ref { def_id: next_ref_id } = &self.defs.get(ref_id).unwrap().rules[0].body {
-        if next_ref_id == def_id {
+        if next_ref_id == ref_id {
           return Err(format!(
             "Definition {} is a reference to itself",
-            self.def_names.name(def_id).unwrap()
+            self.def_names.name(ref_id).unwrap()
           ));
         }
         ref_id = next_ref_id;

tests/golden_tests.rs

@@ -170,7 +170,7 @@ fn encode_pattern_match() {
     book.encode_strs()?;
     book.encode_lists()?;
     book.generate_scott_adts();
-    book.resolve_refs();
+    book.resolve_refs()?;
     encode_pattern_matching(&mut book)?;
     Ok(book.to_string())
   })

tests/golden_tests/compile_file/ref_to_main.hvm

@@ -0,0 +1,2 @@
+Foo = Main
+main = Foo

tests/golden_tests/compile_file/self_ref.hvm

@@ -1 +1,2 @@
-main = main
+Foo = Foo
+main = Foo

tests/golden_tests/run_file/readback_hvm1_main.hvm

@@ -1 +0,0 @@
-Main = λa Main

tests/golden_tests/run_file/readback_hvm2_main.hvm

@@ -1 +0,0 @@
-main = λa main

tests/snapshots/compile_file__ref_to_main.hvm.snap

@@ -0,0 +1,5 @@
+---
+source: tests/golden_tests.rs
+input_file: tests/golden_tests/compile_file/ref_to_main.hvm
+---
+Main definition can't be referenced inside the program

tests/snapshots/compile_file__self_ref.hvm.snap

@@ -2,4 +2,4 @@
 source: tests/golden_tests.rs
 input_file: tests/golden_tests/compile_file/self_ref.hvm
 ---
-Definition main is a reference to itself
+Definition Foo is a reference to itself

tests/snapshots/run_file__readback_hvm1_main.hvm.snap

@@ -1,5 +0,0 @@
----
-source: tests/golden_tests.rs
-input_file: tests/golden_tests/run_file/readback_hvm1_main.hvm
----
-λ* Main

tests/snapshots/run_file__readback_hvm2_main.hvm.snap

@@ -1,5 +0,0 @@
----
-source: tests/golden_tests.rs
-input_file: tests/golden_tests/run_file/readback_hvm2_main.hvm
----
-λ* main