[Bug]: Symbol table lookup for incomplete RecordDecl might return TypeDef

[Jezurko]

Prerequisites

• I have read the documentation and the proposed feature is not implemented.

Description

Looking up symbol using the default_symbol_mangler::symbol() method to find a decl missing a body might return typedef op. This is troublesome, as we expect it to be an incomplete RecordDecl and we try to add the body to the typedef.
Example reproducer (based on LLVM SingleSource TS: SingleSource/Regression/C/gcc-c-torture/execute/20040703-1.c)

typedef unsigned int cpp_num_part;
typedef struct cpp_num cpp_num;
struct cpp_num
{
   cpp_num_part high;
   cpp_num_part low;
   int unsignedp;
   int overflow; 
};