foo.cc: In function 'int f(int)':
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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