cmd/vet: better align print warnings with fmt

fmt's %d, %x, and %X all accept pointer arguments. However, in cmd/vet's
printVerbs table, they were defined as if they did not accept pointer
arguments.

This inconsistency with fmt did not manifest to users since the vet
codebase worked around it. In particular, pointer arguments were usually
allowed for verbs that accepted integers, as the *types.Pointer argument
type case read the following:

	t&(argInt|argPointer) != 0

As a result, using the %q verb with a pointer resulted in a bug in
cmd/vet:

	$ go run f.go
	%!q(*int=0xc000014140)
	$ go vet f.go
	[no warning]

As documented, fmt's %q verb only accepts runes (integers), strings, and
byte slices. It should not accept pointers, and it does not. But since
vet mixed integers and pointers, it wasn't properly warning about the
misuse of fmt.

This patch surfaced another bug with fmt.Printf("%p", nil):

	$ go run f.go
	%!p(<nil>)
	$ go vet f.go
	[no warning]

As documented, fmt's %p verb only accepts pointers, and untyped nil is
not a valid pointer. But vet did not warn about it, which is another
inconsistency with fmt's documented rules. Fix that too, with a test,
also getting rid of the TODO associated with the code.

As a result of those changes, fix a wrong use of the fmt format verbs in
the standard library, now correctly spotted by vet.

Fixes #25233.

Change-Id: Id0ad31fbc25adfe1c46c6b6879b8d02b23633b3a
Reviewed-on: https://go-review.googlesource.com/111284
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>

4 files changed, 10 insertions, 8 deletions

diff --git a/src/cmd/vet/print.go b/src/cmd/vet/print.go
index 294688f4ea..e4e99641ef 100644
--- a/src/cmd/vet/print.go
+++ b/src/cmd/vet/print.go
@@ -534,7 +534,7 @@ var printVerbs = []printVerb{
 	{'%', noFlag, 0},
 	{'b', numFlag, argInt | argFloat | argComplex},
 	{'c', "-", argRune | argInt},
-	{'d', numFlag, argInt},
+	{'d', numFlag, argInt | argPointer},
 	{'e', sharpNumFlag, argFloat | argComplex},
 	{'E', sharpNumFlag, argFloat | argComplex},
 	{'f', sharpNumFlag, argFloat | argComplex},
@@ -549,8 +549,8 @@ var printVerbs = []printVerb{
 	{'T', "-", anyType},
 	{'U', "-#", argRune | argInt},
 	{'v', allFlags, anyType},
-	{'x', sharpNumFlag, argRune | argInt | argString},
-	{'X', sharpNumFlag, argRune | argInt | argString},
+	{'x', sharpNumFlag, argRune | argInt | argString | argPointer},
+	{'X', sharpNumFlag, argRune | argInt | argString | argPointer},
 }
 
 // okPrintfArg compares the formatState to the arguments actually present,
diff --git a/src/cmd/vet/testdata/print.go b/src/cmd/vet/testdata/print.go
index 1669a047da..459b08141b 100644
--- a/src/cmd/vet/testdata/print.go
+++ b/src/cmd/vet/testdata/print.go
@@ -79,7 +79,7 @@ func PrintfTests() {
 	fmt.Printf("%G %G %G %G", 3e9, x, fslice, c)
 	fmt.Printf("%b %b %b %b", 3e9, x, fslice, c)
 	fmt.Printf("%o %o", 3, i)
-	fmt.Printf("%p %p", p, nil)
+	fmt.Printf("%p", p)
 	fmt.Printf("%q %q %q %q", 3, i, 'x', r)
 	fmt.Printf("%s %s %s", "hi", s, []byte{65})
 	fmt.Printf("%t %t", true, b)
@@ -122,6 +122,7 @@ func PrintfTests() {
 	fmt.Printf("%g", imap)                      // ERROR "Printf format %g has arg imap of wrong type map\[int\]int"
 	fmt.Printf("%G", i)                         // ERROR "Printf format %G has arg i of wrong type int"
 	fmt.Printf("%o", x)                         // ERROR "Printf format %o has arg x of wrong type float64"
+	fmt.Printf("%p", nil)                       // ERROR "Printf format %p has arg nil of wrong type untyped nil"
 	fmt.Printf("%p", 23)                        // ERROR "Printf format %p has arg 23 of wrong type int"
 	fmt.Printf("%q", x)                         // ERROR "Printf format %q has arg x of wrong type float64"
 	fmt.Printf("%s", b)                         // ERROR "Printf format %s has arg b of wrong type bool"
@@ -180,6 +181,7 @@ func PrintfTests() {
 	Printf("%d", notPercentDV)  // ERROR "Printf format %d has arg notPercentDV of wrong type testdata.notPercentDStruct"
 	Printf("%d", &notPercentDV) // ERROR "Printf format %d has arg &notPercentDV of wrong type \*testdata.notPercentDStruct"
 	Printf("%p", &notPercentDV) // Works regardless: we print it as a pointer.
+	Printf("%q", &percentDV)    // ERROR "Printf format %q has arg &percentDV of wrong type \*testdata.percentDStruct"
 	Printf("%s", percentSV)
 	Printf("%s", &percentSV)
 	// Good argument reorderings.
diff --git a/src/cmd/vet/types.go b/src/cmd/vet/types.go
index ea4269a7f9..5f8e481e01 100644
--- a/src/cmd/vet/types.go
+++ b/src/cmd/vet/types.go
@@ -201,8 +201,8 @@ func (f *File) matchArgTypeInternal(t printfArgType, typ types.Type, arg ast.Exp
 		if str, ok := typ.Elem().Underlying().(*types.Struct); ok {
 			return f.matchStructArgType(t, str, arg, inProgress)
 		}
-		// The rest can print with %p as pointers, or as integers with %x etc.
-		return t&(argInt|argPointer) != 0
+		// Check whether the rest can print pointers.
+		return t&argPointer != 0
 
 	case *types.Struct:
 		return f.matchStructArgType(t, typ, arg, inProgress)
@@ -254,7 +254,7 @@ func (f *File) matchArgTypeInternal(t printfArgType, typ types.Type, arg ast.Exp
 			return t&(argInt|argRune) != 0
 
 		case types.UntypedNil:
-			return t&argPointer != 0 // TODO?
+			return false
 
 		case types.Invalid:
 			if *verbose {
diff --git a/src/time/zoneinfo_test.go b/src/time/zoneinfo_test.go
index 7a55d4f618..450f5aa114 100644
--- a/src/time/zoneinfo_test.go
+++ b/src/time/zoneinfo_test.go
@@ -32,7 +32,7 @@ func TestEnvVarUsage(t *testing.T) {
 	defer time.ResetZoneinfoForTesting()
 
 	if zoneinfo := time.ZoneinfoForTesting(); testZoneinfo != *zoneinfo {
-		t.Errorf("zoneinfo does not match env variable: got %q want %q", zoneinfo, testZoneinfo)
+		t.Errorf("zoneinfo does not match env variable: got %q want %q", *zoneinfo, testZoneinfo)
 	}
 }