Fix narrowing conversion warnings

gcc/rust/checks/errors/borrowck/rust-bir-place.h

@@ -204,6 +204,9 @@ template <typename I, typename T> class IndexVec
 {
   std::vector<T> internal_vector;
 
+  typedef decltype (std::declval<I> ().value) size_type;
+  static constexpr auto MAX_INDEX = std::numeric_limits<size_type>::max ();
+
 public:
   IndexVec () = default;
   IndexVec (size_t size) { internal_vector.reserve (size); }
@@ -219,7 +222,11 @@ template <typename I, typename T> class IndexVec
     internal_vector.emplace_back (std::forward<Args> (args)...);
   }
 
-  size_t size () const { return internal_vector.size (); }
+  size_type size () const
+  {
+    rust_assert (internal_vector.size () < MAX_INDEX);
+    return static_cast<size_type> (internal_vector.size ());
+  }
 
   std::vector<T> &get_vector () { return internal_vector; }
 };
@@ -418,8 +425,7 @@ class PlaceDB
     if (lookup != INVALID_PLACE)
       return lookup;
 
-    add_place ({Place::VARIABLE, id, {}, is_type_copy (tyty), tyty});
-    return {places.size () - 1};
+    return add_place ({Place::VARIABLE, id, {}, is_type_copy (tyty), tyty});
   };
 
   template <typename FN> void for_each_path_from_root (PlaceId var, FN fn) const

gcc/rust/checks/errors/borrowck/rust-bir.h

@@ -35,6 +35,26 @@ using BasicBlocks = IndexVec<BasicBlockId, BasicBlock>;
 class Statement;
 class AbstractExpr;
 
+/** Unique identifier for a basic block in the BIR. */
+struct BasicBlockId
+{
+  uint32_t value;
+  // some overloads for comparision
+  bool operator== (const BasicBlockId &rhs) const { return value == rhs.value; }
+  bool operator!= (const BasicBlockId &rhs) const
+  {
+    return !(operator== (rhs));
+  }
+  bool operator< (const BasicBlockId &rhs) const { return value < rhs.value; }
+  bool operator> (const BasicBlockId &rhs) const { return value > rhs.value; }
+  bool operator<= (const BasicBlockId &rhs) const { return !(operator> (rhs)); }
+  bool operator>= (const BasicBlockId &rhs) const { return !(operator< (rhs)); }
+};
+
+static constexpr BasicBlockId INVALID_BB
+  = {std::numeric_limits<uint32_t>::max ()};
+static constexpr BasicBlockId ENTRY_BASIC_BLOCK = {0};
+
 /**
  * Top-level entity of the Borrow-checker IR (BIR).
  * It represents a single function (method, closure, etc.), which is the
@@ -132,26 +152,6 @@ class Statement
   WARN_UNUSED_RESULT location_t get_location () const { return location; }
 };
 
-/** Unique identifier for a basic block in the BIR. */
-struct BasicBlockId
-{
-  uint32_t value;
-  // some overloads for comparision
-  bool operator== (const BasicBlockId &rhs) const { return value == rhs.value; }
-  bool operator!= (const BasicBlockId &rhs) const
-  {
-    return !(operator== (rhs));
-  }
-  bool operator< (const BasicBlockId &rhs) const { return value < rhs.value; }
-  bool operator> (const BasicBlockId &rhs) const { return value > rhs.value; }
-  bool operator<= (const BasicBlockId &rhs) const { return !(operator> (rhs)); }
-  bool operator>= (const BasicBlockId &rhs) const { return !(operator< (rhs)); }
-};
-
-static constexpr BasicBlockId INVALID_BB
-  = {std::numeric_limits<uint32_t>::max ()};
-static constexpr BasicBlockId ENTRY_BASIC_BLOCK = {0};
-
 struct BasicBlock
 {
   // BIR "instructions".