exclude maphash methods that "never fail"

errcheck/excludes.go

@@ -47,6 +47,11 @@ var DefaultExcludedSymbols = []string{
 
 	// hash
 	"(hash.Hash).Write",
+
+	// hash/maphash
+	"(*hash/maphash.Hash).Write",
+	"(*hash/maphash.Hash).WriteByte",
+	"(*hash/maphash.Hash).WriteString",
 }
 
 // ReadExcludes reads an excludes file, a newline delimited file that lists

testdata/hash.go

@@ -0,0 +1,17 @@
+package main
+
+import (
+	"crypto/sha256"
+	"hash/maphash"
+)
+
+func ignoreHashReturns() {
+	sha256.New().Write([]byte{}) // EXCLUDED
+}
+
+func ignoreHashMapReturns() {
+	var hasher maphash.Hash
+	hasher.Write(nil)      // EXCLUDED
+	hasher.WriteByte(0)    // EXCLUDED
+	hasher.WriteString("") // EXCLUDED
+}

testdata/main.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"bytes"
-	"crypto/sha256"
 	"fmt"
 	"io"
 	"math/rand"
@@ -147,7 +146,6 @@ func main() {
 	b2.Write(nil)
 	rand.Read(nil)
 	mrand.Read(nil)
-	sha256.New().Write([]byte{})
 	pr, pw := io.Pipe()
 	pr.CloseWithError(nil)
 	pw.CloseWithError(nil)