Initial TypeCast Rules

This gives us full explicit control for all casting. Just like other
rules. More test cases are needed to close out type-casts by the the end of
the traits milestone.

Fixes #592

Author: philberty

gcc/rust/typecheck/rust-hir-type-check-expr.h

@@ -1147,6 +1147,16 @@ class TypeCheckExpr : public TypeCheckBase
       }
   }
 
+  void visit (HIR::TypeCastExpr &expr) override
+  {
+    TyTy::BaseType *expr_to_convert
+      = TypeCheckExpr::Resolve (expr.get_casted_expr ().get (), false);
+    TyTy::BaseType *tyty_to_convert_to
+      = TypeCheckType::Resolve (expr.get_type_to_convert_to ().get ());
+
+    infered = expr_to_convert->cast (tyty_to_convert_to);
+  }
+
 private:
   TypeCheckExpr (bool inside_loop)
     : TypeCheckBase (), infered (nullptr), infered_array_elems (nullptr),