YES IT IS SYNTAX ERROR BECAUSE
FORM /* to last */ taken as comments
so lexems are in,t, gate,; etc
so it is syntactically incorrect but lexically correct.
Some compilers do allow nesting of comments, but that also causes syntax error here as comments are not properly nested.
Output from gcc:
comment.c:4:2: error: unknown type name ‘in’
in/*comment t x;
^
comment.c:5:19: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘gate’
floa/*comment*/t gate;