gc: better error message for bad type in channel send
gc: better error message for bad type in channel send

# test program
1 package main
2
3 type C chan int
4
5 func F(c C) {
6 	c <- true
7 }

# old error
test.go:6: cannot use true (type bool) as type int in function argument

# new error
test.go:6: cannot use true (type bool) as type int in channel send

R=rsc, ejsherry
CC=golang-dev
http://codereview.appspot.com/3231042

Committer: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

pombredanne/go-deleteme,dsriram/golang,h8liu/golang,pombredanne/go-deleteme,tv42/old-go,ssrl/go,ssrl/go,gnanderson/go,dsriram/golang,ssrl/go,ssrl/go,apparentlymart/golang,gnanderson/go,gnanderson/go,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,dsriram/golang,apparentlymart/golang,tv42/old-go,dsriram/golang,gnanderson/go,pombredanne/go-deleteme,pombredanne/go-deleteme,apparentlymart/golang,h8liu/golang,h8liu/golang,ssrl/go,ssrl/go,gnanderson/go,tv42/old-go,tv42/old-go,dsriram/golang,h8liu/golang,gnanderson/go,tv42/old-go,dsriram/golang,apparentlymart/golang,apparentlymart/golang,h8liu/golang,dsriram/golang,apparentlymart/golang,h8liu/golang,ssrl/go,apparentlymart/golang,gnanderson/go,h8liu/golang