If 'swift' is invoked with command line options that are only pertinent to 'swiftc', the error message that results should cut to the chase and emphasize that the user probably wants to invoke 'swiftc'. The inclusion of the inapplicable options in the "did you mean" text leads users (well, me anyway) to scrutinize the choice of option, rather than the choice of tool name.
From the Terminal, run:
Results in an error:
<unknown>:0: error: unsupported option '-emit-assembly' for 'swift'; did you mean 'swiftc -emit-assembly'?
I think it would be less confusing if the error message emphasized the likely wrong choice of command line tool:
<unknown>:0: error: unsupported option '-emit-assembly' for 'swift'; did you mean to use 'swiftc'?