cmd/vet: %T is a formatting directive too

Some warnings were being missed, because vet's regex that finds
formatting directives was missing the 'T' verb.

Fixes #24646.

Change-Id: I2f6f9ed19e7daf9a07175199f428a62e94799ea9
Reviewed-on: https://go-review.googlesource.com/111357
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Rob Pike <r@golang.org>

src/cmd/vet/print.go

@@ -721,7 +721,7 @@ const (
 	flagsRE    = `[+\-#]*`
 	indexOptRE = `(\[[0-9]+\])?`
 	numOptRE   = `([0-9]+|` + indexOptRE + `\*)?`
-	verbRE     = `[bcdefgopqstvxEFGUX]`
+	verbRE     = `[bcdefgopqstvxEFGTUX]`
 )
 
 // checkPrint checks a call to an unformatted print routine such as Println.

src/cmd/vet/testdata/print.go

@@ -148,6 +148,7 @@ func PrintfTests() {
 	fmt.Println()                               // not an error
 	fmt.Println("%s", "hi")                     // ERROR "Println call has possible formatting directive %s"
 	fmt.Println("%v", "hi")                     // ERROR "Println call has possible formatting directive %v"
+	fmt.Println("%T", "hi")                     // ERROR "Println call has possible formatting directive %T"
 	fmt.Println("0.0%")                         // correct (trailing % couldn't be a formatting directive)
 	fmt.Printf("%s", "hi", 3)                   // ERROR "Printf call needs 1 arg but has 2 args"
 	_ = fmt.Sprintf("%"+("s"), "hi", 3)         // ERROR "Sprintf call needs 1 arg but has 2 args"