all: remove now-unnecessary unreachable panics

Take advantage of the new terminating statement rule.

R=golang-dev, r, gri
CC=golang-dev
https://golang.org/cl/7712044

src/cmd/api/goapi.go

@@ -723,7 +723,6 @@ func (w *Walker) varValueType(vi interface{}) (string, error) {
 	default:
 		return "", fmt.Errorf("unknown const value type %T", vi)
 	}
-	panic("unreachable")
 }
 
 // resolveName finds a top-level node named name and returns the node

src/cmd/go/build.go

@@ -1291,7 +1291,6 @@ func (b *builder) runOut(dir string, desc string, cmdargs ...interface{}) ([]byt
 
 		return buf.Bytes(), err
 	}
-	panic("unreachable")
 }
 
 // mkdir makes the named directory.

src/pkg/bufio/bufio.go

@@ -274,7 +274,6 @@ func (b *Reader) ReadSlice(delim byte) (line []byte, err error) {
 			return b.buf, ErrBufferFull
 		}
 	}
-	panic("not reached")
 }
 
 // ReadLine is a low-level line-reading primitive. Most callers should use

src/pkg/bufio/scan.go

@@ -169,7 +169,6 @@ func (s *Scanner) Scan() bool {
 		}
 		s.end += n
 	}
-	panic("not reached")
 }
 
 // advance consumes n bytes of the buffer. It reports whether the advance was legal.

src/pkg/compress/bzip2/huffman.go

@@ -54,8 +54,6 @@ func (t huffmanTree) Decode(br *bitReader) (v uint16) {
 			nodeIndex = node.right
 		}
 	}
-
-	panic("unreachable")
 }
 
 // newHuffmanTree builds a Huffman tree from a slice containing the code

src/pkg/compress/flate/deflate_test.go

@@ -158,7 +158,6 @@ func (b *syncBuffer) Read(p []byte) (n int, err error) {
 		}
 		<-b.ready
 	}
-	panic("unreachable")
 }
 
 func (b *syncBuffer) signal() {

src/pkg/compress/flate/inflate.go

@@ -263,7 +263,6 @@ func (f *decompressor) Read(b []byte) (int, error) {
 		}
 		f.step(f)
 	}
-	panic("unreachable")
 }
 
 func (f *decompressor) Close() error {
@@ -495,7 +494,6 @@ func (f *decompressor) huffmanBlock() {
 			return
 		}
 	}
-	panic("unreached")
 }
 
 // copyHist copies f.copyLen bytes from f.hist (f.copyDist bytes ago) to itself.

src/pkg/compress/flate/token.go

@@ -99,5 +99,4 @@ func offsetCode(off uint32) uint32 {
 	default:
 		return offsetCodes[off>>14] + 28
 	}
-	panic("unreachable")
 }

src/pkg/compress/lzw/reader.go

@@ -121,7 +121,6 @@ func (d *decoder) Read(b []byte) (int, error) {
 		}
 		d.decode()
 	}
-	panic("unreachable")
 }
 
 // decode decompresses bytes from r and leaves them in d.toRead.

src/pkg/crypto/dsa/dsa.go

@@ -144,8 +144,6 @@ GeneratePrimes:
 		params.G = g
 		return
 	}
-
-	panic("unreachable")
 }
 
 // GenerateKey generates a public&private key pair. The Parameters of the

src/pkg/crypto/x509/pkcs8.go

@@ -51,6 +51,4 @@ func ParsePKCS8PrivateKey(der []byte) (key interface{}, err error) {
 	default:
 		return nil, fmt.Errorf("crypto/x509: PKCS#8 wrapping contained private key with unknown algorithm: %v", privKey.Algo.Algorithm)
 	}
-
-	panic("unreachable")
 }

src/pkg/crypto/x509/x509.go

@@ -729,7 +729,6 @@ func parsePublicKey(algo PublicKeyAlgorithm, keyData *publicKeyInfo) (interface{
 	default:
 		return nil, nil
 	}
-	panic("unreachable")
 }
 
 func parseCertificate(in *certificate) (*Certificate, error) {

src/pkg/encoding/ascii85/ascii85.go

@@ -296,5 +296,4 @@ func (d *decoder) Read(p []byte) (n int, err error) {
 		nn, d.readErr = d.r.Read(d.buf[d.nbuf:])
 		d.nbuf += nn
 	}
-	panic("unreachable")
 }

src/pkg/encoding/binary/varint.go

@@ -120,7 +120,6 @@ func ReadUvarint(r io.ByteReader) (uint64, error) {
 		x |= uint64(b&0x7f) << s
 		s += 7
 	}
-	panic("unreachable")
 }
 
 // ReadVarint reads an encoded signed integer from r and returns it as an int64.

src/pkg/encoding/csv/reader.go

@@ -171,7 +171,6 @@ func (r *Reader) ReadAll() (records [][]string, err error) {
 		}
 		records = append(records, record)
 	}
-	panic("unreachable")
 }
 
 // readRune reads one rune from r, folding \r\n to \n and keeping track

src/pkg/encoding/json/decode.go

@@ -739,6 +739,7 @@ func (d *decodeState) valueInterface() interface{} {
 	switch d.scanWhile(scanSkipSpace) {
 	default:
 		d.error(errPhase)
+		panic("unreachable")
 	case scanBeginArray:
 		return d.arrayInterface()
 	case scanBeginObject:
@@ -746,7 +747,6 @@ func (d *decodeState) valueInterface() interface{} {
 	case scanBeginLiteral:
 		return d.literalInterface()
 	}
-	panic("unreachable")
 }
 
 // arrayInterface is like array but returns []interface{}.

src/pkg/encoding/xml/read.go

@@ -493,7 +493,6 @@ Loop:
 			return true, nil
 		}
 	}
-	panic("unreachable")
 }
 
 // Skip reads tokens until it has consumed the end element
@@ -517,5 +516,4 @@ func (d *Decoder) Skip() error {
 			return nil
 		}
 	}
-	panic("unreachable")
 }

src/pkg/go/parser/error_test.go

@@ -89,8 +89,6 @@ func expectedErrors(t *testing.T, filename string, src []byte) map[token.Pos]str
 			prev = pos
 		}
 	}
-
-	panic("unreachable")
 }
 
 // compareErrors compares the map of expected error messages with the list

src/pkg/html/template/transition.go

@@ -71,7 +71,6 @@ func tText(c context, s []byte) (context, int) {
 		}
 		k = j
 	}
-	panic("unreachable")
 }
 
 var elementContentType = [...]state{

src/pkg/image/gif/reader.go

@@ -304,7 +304,6 @@ func (d *decoder) readExtension() error {
 			return err
 		}
 	}
-	panic("unreachable")
 }
 
 func (d *decoder) readGraphicControl() error {

src/pkg/io/ioutil/ioutil.go

@@ -144,7 +144,6 @@ func (devNull) ReadFrom(r io.Reader) (n int64, err error) {
 			return
 		}
 	}
-	panic("unreachable")
 }
 
 // Discard is an io.Writer on which all Write calls succeed

src/pkg/math/rand/exp.go

@@ -43,7 +43,6 @@ func (r *Rand) ExpFloat64() float64 {
 			return x
 		}
 	}
-	panic("unreachable")
 }
 
 var ke = [256]uint32{

src/pkg/math/rand/normal.go

@@ -63,7 +63,6 @@ func (r *Rand) NormFloat64() float64 {
 			return x
 		}
 	}
-	panic("unreachable")
 }
 
 var kn = [128]uint32{

src/pkg/mime/multipart/multipart.go

@@ -265,7 +265,6 @@ func (r *Reader) NextPart() (*Part, error) {
 
 		return nil, fmt.Errorf("multipart: unexpected line in Next(): %q", line)
 	}
-	panic("unreachable")
 }
 
 // isFinalBoundary returns whether line is the final boundary line

src/pkg/net/dial.go

@@ -280,7 +280,6 @@ func dialTimeoutRace(net, addr string, timeout time.Duration) (Conn, error) {
 	case p := <-ch:
 		return p.Conn, p.error
 	}
-	panic("unreachable")
 }
 
 type stringAddr struct {

src/pkg/net/http/client_test.go

@@ -51,7 +51,6 @@ func pedanticReadAll(r io.Reader) (b []byte, err error) {
 			return b, err
 		}
 	}
-	panic("unreachable")
 }
 
 func TestClient(t *testing.T) {

src/pkg/net/http/fcgi/child.go

@@ -267,5 +267,4 @@ func Serve(l net.Listener, handler http.Handler) error {
 		c := newChild(rw, handler)
 		go c.serve()
 	}
-	panic("unreachable")
 }

src/pkg/net/http/server.go

@@ -1337,7 +1337,6 @@ func (srv *Server) Serve(l net.Listener) error {
 		}
 		go c.serve()
 	}
-	panic("not reached")
 }
 
 // ListenAndServe listens on the TCP network address addr

src/pkg/net/http/transport.go

@@ -349,7 +349,6 @@ func (t *Transport) getIdleConn(cm *connectMethod) (pconn *persistConn) {
 			return
 		}
 	}
-	panic("unreachable")
 }
 
 func (t *Transport) setReqConn(r *Request, pc *persistConn) {

src/pkg/net/rpc/server_test.go

@@ -399,12 +399,10 @@ func (WriteFailCodec) WriteRequest(*Request, interface{}) error {
 
 func (WriteFailCodec) ReadResponseHeader(*Response) error {
 	select {}
-	panic("unreachable")
 }
 
 func (WriteFailCodec) ReadResponseBody(interface{}) error {
 	select {}
-	panic("unreachable")
 }
 
 func (WriteFailCodec) Close() error {

src/pkg/net/textproto/reader.go

@@ -489,7 +489,6 @@ func (r *Reader) ReadMIMEHeader() (MIMEHeader, error) {
 			return m, err
 		}
 	}
-	panic("unreachable")
 }
 
 // CanonicalMIMEHeaderKey returns the canonical format of the

src/pkg/os/file_unix.go

@@ -198,7 +198,6 @@ func (f *File) write(b []byte) (n int, err error) {
 
 		return n, err
 	}
-	panic("not reached")
 }
 
 // pwrite writes len(b) bytes to the File starting at byte offset off.