Merge #433

433: Allow unused underscore identifiers r=philberty a=CohenArthur

This fixes #361 

Co-authored-by: CohenArthur <arthur.cohen@epita.fr>

6 files changed, 25 insertions, 4 deletions

diff --git a/gcc/rust/resolve/rust-ast-resolve-unused.h b/gcc/rust/resolve/rust-ast-resolve-unused.h
index 748f972..bd71110 100644
--- a/gcc/rust/resolve/rust-ast-resolve-unused.h
+++ b/gcc/rust/resolve/rust-ast-resolve-unused.h
@@ -30,7 +30,13 @@ public:
   static void ScanRib (Rib *r)
   {
     r->iterate_decls ([&] (NodeId decl_node_id, Location locus) -> bool {
-      if (!r->have_references_for_node (decl_node_id))
+      CanonicalPath ident = CanonicalPath::create_empty ();
+
+      bool ok = r->lookup_canonical_path (decl_node_id, &ident);
+      rust_assert (ok);
+
+      if (!r->have_references_for_node (decl_node_id)
+	  && ident.get ().at (0) != '_')
 	{
 	  rust_warning_at (locus, 0, "unused name");
 	}
diff --git a/gcc/rust/resolve/rust-name-resolver.h b/gcc/rust/resolve/rust-name-resolver.h
index 205c877..e45847e 100644
--- a/gcc/rust/resolve/rust-name-resolver.h
+++ b/gcc/rust/resolve/rust-name-resolver.h
@@ -114,6 +114,7 @@ public:
       }
 
     mappings[path] = id;
+    reverse_mappings.insert (std::pair<NodeId, CanonicalPath> (id, path));
     decls_within_rib.insert (std::pair<NodeId, Location> (id, locus));
     references[id] = {};
   }
@@ -128,9 +129,21 @@ public:
     return true;
   }
 
+  bool lookup_canonical_path (const NodeId &id, CanonicalPath *ident)
+  {
+    auto it = reverse_mappings.find (id);
+    if (it == reverse_mappings.end ())
+      return false;
+
+    *ident = it->second;
+    return true;
+  }
+
   void clear_name (const CanonicalPath &ident, NodeId id)
   {
     mappings.erase (ident);
+    reverse_mappings.erase (id);
+
     for (auto &it : decls_within_rib)
       {
 	if (it.first == id)
@@ -194,6 +207,7 @@ private:
   CrateNum crate_num;
   NodeId node_id;
   std::map<CanonicalPath, NodeId> mappings;
+  std::map<NodeId, CanonicalPath> reverse_mappings;
   std::set<std::pair<NodeId, Location> > decls_within_rib;
   std::map<NodeId, std::set<NodeId> > references;
 };
diff --git a/gcc/testsuite/rust.test/compile/loop5.rs b/gcc/testsuite/rust.test/compile/loop5.rs
index 06f5f9e..4004cd3 100644
--- a/gcc/testsuite/rust.test/compile/loop5.rs
+++ b/gcc/testsuite/rust.test/compile/loop5.rs
@@ -4,7 +4,6 @@ fn main() {
 
     // first number in Fibonacci sequence over 10:
     let _fib = loop {
-        // { dg-bogus "unused name" "#361" { xfail *-*-* } .-1 }
         if b > 10 {
             break b;
         }
diff --git a/gcc/testsuite/rust.test/compile/loop7.rs b/gcc/testsuite/rust.test/compile/loop7.rs
index 647df13..0cd8445 100644
--- a/gcc/testsuite/rust.test/compile/loop7.rs
+++ b/gcc/testsuite/rust.test/compile/loop7.rs
@@ -3,7 +3,6 @@ fn main() {
     let mut b = 1;
 
     let _fib = loop {
-        // { dg-bogus "unused name" "#361" { xfail *-*-* } .-1 }
         if (a % 2 == 0) {
             continue;
         }
diff --git a/gcc/testsuite/rust.test/compile/struct_base_init_1.rs b/gcc/testsuite/rust.test/compile/struct_base_init_1.rs
index 781265a..3c0b24a 100644
--- a/gcc/testsuite/rust.test/compile/struct_base_init_1.rs
+++ b/gcc/testsuite/rust.test/compile/struct_base_init_1.rs
@@ -9,5 +9,4 @@ fn foo() -> Foo {
 
 fn main() {
     let _f = Foo { a: 10, ..foo() };
-    // { dg-bogus "unused name" "#361" { xfail *-*-* } .-1 }
 }
diff --git a/gcc/testsuite/rust.test/compile/underscore_id.rs b/gcc/testsuite/rust.test/compile/underscore_id.rs
new file mode 100644
index 0000000..2c106c5
--- /dev/null
+++ b/gcc/testsuite/rust.test/compile/underscore_id.rs
@@ -0,0 +1,4 @@
+fn main() {
+    let _unused_but_fine = 12;
+    let unused = 12; // { dg-warning "unused name" }
+}