Allow for coercion of structures over to dynamic objects in type system

This is the initial support for allowing a coercion of something like:

```rust
let a = Foo(123);
let b:&dyn Bound = &a;
```

The coercion will need to ensure that 'a' meets the specified bounds of the
dynamic object.

Addresses #197

2 files changed, 24 insertions, 0 deletions

diff --git a/gcc/rust/typecheck/rust-tyty-coercion.h b/gcc/rust/typecheck/rust-tyty-coercion.h
index d46f1d4..976997d 100644
--- a/gcc/rust/typecheck/rust-tyty-coercion.h
+++ b/gcc/rust/typecheck/rust-tyty-coercion.h
@@ -24,6 +24,7 @@
 #include "rust-tyty-visitor.h"
 #include "rust-hir-map.h"
 #include "rust-hir-type-check.h"
+#include "rust-hir-type-bounds.h"
 
 extern ::Backend *
 rust_get_backend ();
@@ -1390,6 +1391,16 @@ public:
     resolved = base->clone ();
   }
 
+  void visit (ADTType &type) override
+  {
+    Location ref_locus = mappings->lookup_location (type.get_ref ());
+    bool ok = base->bounds_compatible (type, ref_locus, true);
+    if (!ok)
+      return;
+
+    resolved = base->clone ();
+  }
+
 private:
   BaseType *get_base () override { return base; }
 
diff --git a/gcc/testsuite/rust/compile/traits9.rs b/gcc/testsuite/rust/compile/traits9.rs
new file mode 100644
index 0000000..e1aef539
--- /dev/null
+++ b/gcc/testsuite/rust/compile/traits9.rs
@@ -0,0 +1,13 @@
+struct Foo(i32);
+trait Bar {
+    fn baz(&self);
+}
+
+fn main() {
+    let a;
+    a = Foo(123);
+
+    let b: &dyn Bar = &a;
+    // { dg-error "bounds not satisfied for Foo .Bar. is not satisfied" "" { target *-*-* } .-1 }
+    // { dg-error "expected" "" { target *-*-* } .-2 }
+}