Created attachment 201721 [details]
simple example of the bug

atached example where in two blocks the same variable name is used in a async method
this generate invalid C code where the same name is used twice in the structure holding
variables of async method. You can see the error message of compilation of blocks.vala:

$ valac --pkg gio-2.0 blocks.vala 
blocks.vala:3.11-3.11: warning: local variable `i' declared but never used
    { int i; }
          ^
blocks.vala:4.11-4.11: warning: local variable `i' declared but never used
    { int i; }
          ^
/home/lupan/src/sidle/blocks.vala.c:17:7: error: duplicate member ‘i’
error: cc exited with status 256
Compilation failed: 1 error(s), 2 warning(s)