compiler: add new debugging helper function debug_go_type()

    
    Add a new debugging utility routine debug_go_type(), intended to
    display the contents of a Type object in a way useful to debugging
    a run of the compiler.  Prior to this the only useful alternative
    for debugging types was invoking the mangled_name() method, which
    has problems (for example, won't work on interface types prior
    to finalizing of methods).
    
    This is a "deep" dump, meaning that all types reachable from the
    type passed to debug_go_type() will be printed out. Example:
    
    (gdb) print debug_go_type(t1)
          T0        0x535f300  'net/http.Header' -> T1
          T1        0x535d3d0  map ['string' -> string] T4
          T2        0x5304bb0  'string' -> string
          T3        0x331f900  string
          T4        0x535d370  array [] 'string' -> string
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/166637

From-SVN: r269633

gcc/go/gofrontend/MERGE

-3106ec19626d75d8275be16c86421132548fa13e
+565b5cd0f49a00ca20941ea042c07ebe6ddf3553
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

gcc/go/gofrontend/types.cc

@@ -6951,7 +6951,7 @@ Type::make_struct_type(Struct_field_list* fields,
 // called for a slice.
 
 bool
-Array_type::int_length(int64_t* plen)
+Array_type::int_length(int64_t* plen) const
 {
   go_assert(this->length_ != NULL);
   Numeric_constant nc;

gcc/go/gofrontend/types.h

@@ -2706,7 +2706,7 @@ class Array_type : public Type
   // length can not be determined.  This will assert if called for a
   // slice.
   bool
-  int_length(int64_t* plen);
+  int_length(int64_t* plen) const;
 
   // Whether this type is identical with T.
   bool
@@ -3160,6 +3160,11 @@ class Interface_type : public Type
   static Type*
   make_interface_type_descriptor_type();
 
+  // Return whether methods are finalized for this interface.
+  bool
+  methods_are_finalized() const
+  { return this->methods_are_finalized_; }
+
  protected:
   int
   do_traverse(Traverse*);