gccrs: Initial support for Return Position Impl Trait

This is the initial patch for RPIT, we can build on this to handle the
more complex cases but there are enough distinct changes going on here
that it should just get merged now.

RPIT is really a sneaky generic so for example:

  fn foo() -> impl Bar {
      Baz
  }

This is represented as: fn () -> OpaqueType Bar. But when we handle the
coercion site for Baz on impl Bar when we type resolve the function we
know that the underlying type  is Baz. Note this function is _not_ generic
so its using this special OpaqueType and keeping track of the underlying type
in its ty_ref reference hir-id which will resolve to Baz.

This also means if we have a case where maybe this was in an if statement:

  fn foo(a: i32) -> impl Bar {
      if a > 10 {
        Baz
      } else {
        Qux
      }
  }

The rules of impl Bar is that Baz is handled but Baz and Qux are different
underlying types so this is not allowed. The reason is impl traits are not
generic and although from a programmer perspective the callers dont know what
the underlying type is, the compiler _knows_ what it is. So really when
you call a function and get its return position impl trait the compiler knows
what to do and does all whats nessecary to handle calling functions using that
type etc.

gcc/rust/ChangeLog:

	* backend/rust-compile-type.cc (TyTyResolveCompile::visit): we need to resolve the
	underlying type
	* typecheck/rust-substitution-mapper.cc (SubstMapperInternal::visit): just clone
	* typecheck/rust-tyty-call.cc (TypeCheckCallExpr::visit):
	ensure we monomphize to get the underlying
	* typecheck/rust-tyty.cc (BaseType::destructure): handle opaque types
	(OpaqueType::resolve): this is much simpler now
	(OpaqueType::handle_substitions): no longer needed
	* typecheck/rust-tyty.h: update header
	* typecheck/rust-unify.cc (UnifyRules::expect_opaque): unify rules for opaque

gcc/testsuite/ChangeLog:

	* rust/compile/bad-rpit1.rs: New test.
	* rust/execute/torture/impl_rpit1.rs: New test.
	* rust/execute/torture/impl_rpit2.rs: New test.
	* rust/execute/torture/impl_rpit3.rs: New test.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>

diff --git a/gcc/rust/backend/rust-compile-type.cc b/gcc/rust/backend/rust-compile-type.cc
index af34c2281f54f7c0bf2cc51b43d77edb638149dd..00b21fbbf952f983cd1557ec596093d70e43bbdd 100644 (file)
--- a/gcc/rust/backend/rust-compile-type.cc
+++ b/gcc/rust/backend/rust-compile-type.cc
@@ -755,7 +755,9 @@ TyTyResolveCompile::visit (const TyTy::DynamicObjectType &type)
 void
 TyTyResolveCompile::visit (const TyTy::OpaqueType &type)
 {
-  translated = error_mark_node;
+  rust_assert (type.can_resolve ());
+  auto underlying = type.resolve ();
+  translated = TyTyResolveCompile::compile (ctx, underlying, trait_object_mode);
 }
 
 tree

diff --git a/gcc/rust/typecheck/rust-substitution-mapper.cc b/gcc/rust/typecheck/rust-substitution-mapper.cc
index f0bd1f8bb17f639ac63a08fe545f963076673041..bdfde55718bedbc837181449d477c0bea3a138d5 100644 (file)
--- a/gcc/rust/typecheck/rust-substitution-mapper.cc
+++ b/gcc/rust/typecheck/rust-substitution-mapper.cc
@@ -374,7 +374,7 @@ SubstMapperInternal::visit (TyTy::DynamicObjectType &type)
 void
 SubstMapperInternal::visit (TyTy::OpaqueType &type)
 {
-  resolved = type.handle_substitions (mappings);
+  resolved = type.clone ();
 }
 
 // SubstMapperFromExisting

diff --git a/gcc/rust/typecheck/rust-tyty-call.cc b/gcc/rust/typecheck/rust-tyty-call.cc
index 5ce31243d9bc5681315b7cb8e070d50e26f633f6..63bb1ff91f800462ba64fdf1c846b7e138cda400 100644 (file)
--- a/gcc/rust/typecheck/rust-tyty-call.cc
+++ b/gcc/rust/typecheck/rust-tyty-call.cc
@@ -251,7 +251,7 @@ TypeCheckCallExpr::visit (FnType &type)
     }
 
   type.monomorphize ();
-  resolved = type.get_return_type ()->clone ();
+  resolved = type.get_return_type ()->monomorphized_clone ();
 }
 
 void

diff --git a/gcc/rust/typecheck/rust-tyty.cc b/gcc/rust/typecheck/rust-tyty.cc
index 83b4c923aa6f0336c72ea35c4b1fee25867b9b9b..91c68efe972dedcbb72580a975c6b3157a97ded1 100644 (file)
--- a/gcc/rust/typecheck/rust-tyty.cc
+++ b/gcc/rust/typecheck/rust-tyty.cc
@@ -548,17 +548,14 @@ BaseType::destructure () const
        {
          x = p->get ();
        }
-      // else if (auto p = x->try_as<const OpaqueType> ())
-      //   {
-      //     auto pr = p->resolve ();
-
-      //     rust_debug ("XXXXXX")
-
-      //     if (pr == x)
-      //       return pr;
+      else if (auto p = x->try_as<const OpaqueType> ())
+       {
+         auto pr = p->resolve ();
+         if (pr == x)
+           return pr;
 
-      //     x = pr;
-      //   }
+         x = pr;
+       }
       else
        {
          return x;
@@ -3643,28 +3640,7 @@ BaseType *
 OpaqueType::resolve () const
 {
   TyVar var (get_ty_ref ());
-  BaseType *r = var.get_tyty ();
-
-  while (r->get_kind () == TypeKind::OPAQUE)
-    {
-      OpaqueType *rr = static_cast<OpaqueType *> (r);
-      if (!rr->can_resolve ())
-       break;
-
-      TyVar v (rr->get_ty_ref ());
-      BaseType *n = v.get_tyty ();
-
-      // fix infinite loop
-      if (r == n)
-       break;
-
-      r = n;
-    }
-
-  if (r->get_kind () == TypeKind::OPAQUE && (r->get_ref () == r->get_ty_ref ()))
-    return TyVar (r->get_ty_ref ()).get_tyty ();
-
-  return r;
+  return var.get_tyty ();
 }
 
 bool
@@ -3674,41 +3650,9 @@ OpaqueType::is_equal (const BaseType &other) const
   if (can_resolve () != other2.can_resolve ())
     return false;
 
-  if (can_resolve ())
-    return resolve ()->can_eq (other2.resolve (), false);
-
   return bounds_compatible (other, UNDEF_LOCATION, false);
 }
 
-OpaqueType *
-OpaqueType::handle_substitions (SubstitutionArgumentMappings &subst_mappings)
-{
-  // SubstitutionArg arg = SubstitutionArg::error ();
-  // bool ok = subst_mappings.get_argument_for_symbol (this, &arg);
-  // if (!ok || arg.is_error ())
-  //   return this;
-
-  // OpaqueType *p = static_cast<OpaqueType *> (clone ());
-  // subst_mappings.on_param_subst (*p, arg);
-
-  // // there are two cases one where we substitute directly to a new PARAM and
-  // // otherwise
-  // if (arg.get_tyty ()->get_kind () == TyTy::TypeKind::PARAM)
-  //   {
-  //     p->set_ty_ref (arg.get_tyty ()->get_ref ());
-  //     return p;
-  //   }
-
-  // // this is the new subst that this needs to pass
-  // p->set_ref (mappings.get_next_hir_id ());
-  // p->set_ty_ref (arg.get_tyty ()->get_ref ());
-
-  // return p;
-
-  rust_unreachable ();
-  return nullptr;
-}
-
 // StrType
 
 StrType::StrType (HirId ref, std::set<HirId> refs)

diff --git a/gcc/rust/typecheck/rust-tyty.h b/gcc/rust/typecheck/rust-tyty.h
index 81e15c896410d8f50a3df42e90862d550f507eec..c759521090da7c2581be51134623c82a3bf37307 100644 (file)
--- a/gcc/rust/typecheck/rust-tyty.h
+++ b/gcc/rust/typecheck/rust-tyty.h
@@ -440,8 +440,6 @@ public:
   std::string get_name () const override final;
 
   bool is_equal (const BaseType &other) const override;
-
-  OpaqueType *handle_substitions (SubstitutionArgumentMappings &mappings);
 };
 
 class StructFieldType

diff --git a/gcc/rust/typecheck/rust-unify.cc b/gcc/rust/typecheck/rust-unify.cc
index 6699f7e46b564b8e9be5d69c04bea2567279c1b6..95463ae947347958bf983ad60eff7fa49e2db540 100644 (file)
--- a/gcc/rust/typecheck/rust-unify.cc
+++ b/gcc/rust/typecheck/rust-unify.cc
@@ -1831,61 +1831,51 @@ UnifyRules::expect_closure (TyTy::ClosureType *ltype, TyTy::BaseType *rtype)
 TyTy::BaseType *
 UnifyRules::expect_opaque (TyTy::OpaqueType *ltype, TyTy::BaseType *rtype)
 {
-  switch (rtype->get_kind ())
+  if (rtype->is<TyTy::OpaqueType> ())
     {
-    case TyTy::INFER:
-      {
-       TyTy::InferType *r = static_cast<TyTy::InferType *> (rtype);
-       bool is_valid
-         = r->get_infer_kind () == TyTy::InferType::InferTypeKind::GENERAL;
-       if (is_valid)
-         return ltype->clone ();
-      }
-      break;
+      TyTy::OpaqueType *ro = rtype->as<TyTy::OpaqueType> ();
+      if (!ltype->is_equal (*ro))
+       return new TyTy::ErrorType (0);
 
-    case TyTy::OPAQUE:
-      {
-       auto &type = *static_cast<TyTy::OpaqueType *> (rtype);
-       if (ltype->num_specified_bounds () != type.num_specified_bounds ())
-         {
-           return new TyTy::ErrorType (0);
-         }
-
-       if (!ltype->bounds_compatible (type, locus, true))
-         {
+      if (ltype->can_resolve () && ro->can_resolve ())
+       {
+         auto lr = ltype->resolve ();
+         auto rr = ro->resolve ();
+
+         auto res = UnifyRules::Resolve (TyTy::TyWithLocation (lr),
+                                         TyTy::TyWithLocation (rr), locus,
+                                         commit_flag, false /* emit_error */,
+                                         infer_flag, commits, infers);
+         if (res->get_kind () == TyTy::TypeKind::ERROR)
            return new TyTy::ErrorType (0);
-         }
-
-       return ltype->clone ();
-      }
-      break;
-
-    case TyTy::CLOSURE:
-    case TyTy::SLICE:
-    case TyTy::PARAM:
-    case TyTy::POINTER:
-    case TyTy::STR:
-    case TyTy::ADT:
-    case TyTy::REF:
-    case TyTy::ARRAY:
-    case TyTy::FNDEF:
-    case TyTy::FNPTR:
-    case TyTy::TUPLE:
-    case TyTy::BOOL:
-    case TyTy::CHAR:
-    case TyTy::INT:
-    case TyTy::UINT:
-    case TyTy::FLOAT:
-    case TyTy::USIZE:
-    case TyTy::ISIZE:
-    case TyTy::NEVER:
-    case TyTy::PLACEHOLDER:
-    case TyTy::PROJECTION:
-    case TyTy::DYNAMIC:
-    case TyTy::ERROR:
-      return new TyTy::ErrorType (0);
+       }
+      else if (ltype->can_resolve ())
+       {
+         auto lr = ltype->resolve ();
+         ro->set_ty_ref (lr->get_ref ());
+       }
+      else if (ro->can_resolve ())
+       {
+         auto rr = ro->resolve ();
+         ltype->set_ty_ref (rr->get_ref ());
+       }
     }
-  return new TyTy::ErrorType (0);
+  else if (ltype->can_resolve ())
+    {
+      auto underly = ltype->resolve ();
+      auto res = UnifyRules::Resolve (TyTy::TyWithLocation (underly),
+                                     TyTy::TyWithLocation (rtype), locus,
+                                     commit_flag, false /* emit_error */,
+                                     infer_flag, commits, infers);
+      if (res->get_kind () == TyTy::TypeKind::ERROR)
+       return new TyTy::ErrorType (0);
+    }
+  else
+    {
+      ltype->set_ty_ref (rtype->get_ref ());
+    }
+
+  return ltype;
 }
 
 } // namespace Resolver

diff --git a/gcc/testsuite/rust/compile/bad-rpit1.rs b/gcc/testsuite/rust/compile/bad-rpit1.rs
new file mode 100644 (file)
index 0000000..d8c21b1
--- /dev/null
+++ b/gcc/testsuite/rust/compile/bad-rpit1.rs
@@ -0,0 +1,26 @@
+#[lang = "sized"]
+trait Sized {}
+
+trait Foo {
+    fn id(&self) -> i32;
+}
+
+struct A;
+struct B;
+
+impl Foo for A {
+    fn id(&self) -> i32 {
+        1
+    }
+}
+
+impl Foo for B {
+    fn id(&self) -> i32 {
+        2
+    }
+}
+
+fn make_foo(cond: bool) -> impl Foo {
+    if cond { A } else { B }
+    // { dg-error "mismatched types, expected .A. but got .B. .E0308." "" { target *-*-* } .-1 }
+}

diff --git a/gcc/testsuite/rust/execute/torture/impl_rpit1.rs b/gcc/testsuite/rust/execute/torture/impl_rpit1.rs
new file mode 100644 (file)
index 0000000..8ce5f21
--- /dev/null
+++ b/gcc/testsuite/rust/execute/torture/impl_rpit1.rs
@@ -0,0 +1,28 @@
+#[lang = "sized"]
+trait Sized {}
+
+trait Foo {
+    fn id(&self) -> i32;
+}
+
+struct Thing(i32);
+
+impl Foo for Thing {
+    fn id(&self) -> i32 {
+        self.0
+    }
+}
+
+fn make_thing(a: i32) -> impl Foo {
+    Thing(a)
+}
+
+fn use_foo(f: impl Foo) -> i32 {
+    f.id()
+}
+
+fn main() -> i32 {
+    let value = make_thing(42);
+    let val = use_foo(value);
+    val - 42
+}

diff --git a/gcc/testsuite/rust/execute/torture/impl_rpit2.rs b/gcc/testsuite/rust/execute/torture/impl_rpit2.rs
new file mode 100644 (file)
index 0000000..f7cbbb6
--- /dev/null
+++ b/gcc/testsuite/rust/execute/torture/impl_rpit2.rs
@@ -0,0 +1,36 @@
+#[lang = "sized"]
+trait Sized {}
+
+trait Foo {
+    fn id(&self) -> i32;
+}
+
+struct Thing(i32);
+
+impl Thing {
+    fn double(&self) -> i32 {
+        // { dg-warning "associated function is never used: .double." "" { target *-*-* } .-1 }
+        self.0 * 2
+    }
+}
+
+impl Foo for Thing {
+    fn id(&self) -> i32 {
+        self.0
+    }
+}
+
+fn make_thing(a: i32) -> impl Foo {
+    Thing(a)
+}
+
+fn use_foo(f: impl Foo) -> i32 {
+    f.id()
+}
+
+fn main() -> i32 {
+    let value = make_thing(21);
+    let id = use_foo(value);
+
+    id - 21
+}

diff --git a/gcc/testsuite/rust/execute/torture/impl_rpit3.rs b/gcc/testsuite/rust/execute/torture/impl_rpit3.rs
new file mode 100644 (file)
index 0000000..dd68eb2
--- /dev/null
+++ b/gcc/testsuite/rust/execute/torture/impl_rpit3.rs
@@ -0,0 +1,25 @@
+#[lang = "sized"]
+trait Sized {}
+
+trait Foo {
+    fn id(&self) -> i32;
+}
+
+struct Thing(i32);
+
+impl Foo for Thing {
+    fn id(&self) -> i32 {
+        self.0
+    }
+}
+
+fn make_thing() -> impl Foo {
+    Thing(99)
+}
+
+fn main() -> i32 {
+    let v = make_thing();
+    let r = &v;
+    let val = r.id();
+    val - 99
+}