foo.cc: In function 'void f(int)':
foo.cc:9:10: error: return-statement with a value, in function returning 'void' [-fpermissive]
    9 |   return n;
      |          ^
foo.cc:14:10: error: return-statement with a value, in function returning 'void' [-fpermissive]
   14 |   return n;
      |          ^
foo.cc:16:15: error: invalid operands of types 'void' and 'void' to binary 'operator+'
   16 |  return f(n-1)+f(n-2);
      |         ~~~~~~^~~~~~~
      |          |      |
      |          void   void
foo.cc:16:21: error: return-statement with a value, in function returning 'void' [-fpermissive]
   16 |  return f(n-1)+f(n-2);
      |                     ^
foo.cc:18:1: error: a function-definition is not allowed here before '{' token
   18 | {
      | ^
foo.cc:23:1: error: expected '}' at end of input
   23 | }
      | ^
foo.cc:5:1: note: to match this '{'
    5 | {
      | ^

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