libgo: update to go1.8rc3

    
    Reviewed-on: https://go-review.googlesource.com/35844

From-SVN: r244981

14 files changed, 389 insertions, 92 deletions

diff --git a/libgo/MERGE b/libgo/MERGE
index 92541df..fa155a2 100644
--- a/libgo/MERGE
+++ b/libgo/MERGE
@@ -1,4 +1,4 @@
-59f181b6fda68ece22882945853ca2df9dbf1c88
+2a5f65a98ca483aad2dd74dc2636a7baecc59cf2
 
 The first line of this file holds the git revision number of the
 last merge done from the master library sources.
diff --git a/libgo/VERSION b/libgo/VERSION
index 212211f..8b33af3 100644
--- a/libgo/VERSION
+++ b/libgo/VERSION
@@ -1 +1 @@
-go1.8rc2
+go1.8rc3
diff --git a/libgo/go/cmd/go/go_test.go b/libgo/go/cmd/go/go_test.go
index 5727eb0..f26c366 100644
--- a/libgo/go/cmd/go/go_test.go
+++ b/libgo/go/cmd/go/go_test.go
@@ -3787,3 +3787,26 @@ GLOBL ·constants<>(SB),8,$8
 	tg.setenv("GOPATH", tg.path("go"))
 	tg.run("build", "p")
 }
+
+// Issue 18778.
+func TestDotDotDotOutsideGOPATH(t *testing.T) {
+	tg := testgo(t)
+	defer tg.cleanup()
+
+	tg.tempFile("pkgs/a.go", `package x`)
+	tg.tempFile("pkgs/a_test.go", `package x_test
+import "testing"
+func TestX(t *testing.T) {}`)
+
+	tg.tempFile("pkgs/a/a.go", `package a`)
+	tg.tempFile("pkgs/a/a_test.go", `package a_test
+import "testing"
+func TestA(t *testing.T) {}`)
+
+	tg.cd(tg.path("pkgs"))
+	tg.run("build", "./...")
+	tg.run("test", "./...")
+	tg.run("list", "./...")
+	tg.grepStdout("pkgs$", "expected package not listed")
+	tg.grepStdout("pkgs/a", "expected package not listed")
+}
diff --git a/libgo/go/cmd/go/pkg.go b/libgo/go/cmd/go/pkg.go
index af8c1d9..61c1b99 100644
--- a/libgo/go/cmd/go/pkg.go
+++ b/libgo/go/cmd/go/pkg.go
@@ -433,7 +433,7 @@ func setErrorPos(p *Package, importPos []token.Position) *Package {
 func cleanImport(path string) string {
 	orig := path
 	path = pathpkg.Clean(path)
-	if strings.HasPrefix(orig, "./") && path != ".." && path != "." && !strings.HasPrefix(path, "../") {
+	if strings.HasPrefix(orig, "./") && path != ".." && !strings.HasPrefix(path, "../") {
 		path = "./" + path
 	}
 	return path
diff --git a/libgo/go/database/sql/sql.go b/libgo/go/database/sql/sql.go
index 0fa7c34..feb9122 100644
--- a/libgo/go/database/sql/sql.go
+++ b/libgo/go/database/sql/sql.go
@@ -1357,16 +1357,7 @@ func (db *DB) begin(ctx context.Context, opts *TxOptions, strategy connReuseStra
 		cancel: cancel,
 		ctx:    ctx,
 	}
-	go func(tx *Tx) {
-		select {
-		case <-tx.ctx.Done():
-			if !tx.isDone() {
-				// Discard and close the connection used to ensure the transaction
-				// is closed and the resources are released.
-				tx.rollback(true)
-			}
-		}
-	}(tx)
+	go tx.awaitDone()
 	return tx, nil
 }
 
@@ -1388,6 +1379,11 @@ func (db *DB) Driver() driver.Driver {
 type Tx struct {
 	db *DB
 
+	// closemu prevents the transaction from closing while there
+	// is an active query. It is held for read during queries
+	// and exclusively during close.
+	closemu sync.RWMutex
+
 	// dc is owned exclusively until Commit or Rollback, at which point
 	// it's returned with putConn.
 	dc  *driverConn
@@ -1413,6 +1409,20 @@ type Tx struct {
 	ctx context.Context
 }
 
+// awaitDone blocks until the context in Tx is canceled and rolls back
+// the transaction if it's not already done.
+func (tx *Tx) awaitDone() {
+	// Wait for either the transaction to be committed or rolled
+	// back, or for the associated context to be closed.
+	<-tx.ctx.Done()
+
+	// Discard and close the connection used to ensure the
+	// transaction is closed and the resources are released.  This
+	// rollback does nothing if the transaction has already been
+	// committed or rolled back.
+	tx.rollback(true)
+}
+
 func (tx *Tx) isDone() bool {
 	return atomic.LoadInt32(&tx.done) != 0
 }
@@ -1424,16 +1434,31 @@ var ErrTxDone = errors.New("sql: Transaction has already been committed or rolle
 // close returns the connection to the pool and
 // must only be called by Tx.rollback or Tx.Commit.
 func (tx *Tx) close(err error) {
+	tx.closemu.Lock()
+	defer tx.closemu.Unlock()
+
 	tx.db.putConn(tx.dc, err)
 	tx.cancel()
 	tx.dc = nil
 	tx.txi = nil
 }
 
+// hookTxGrabConn specifies an optional hook to be called on
+// a successful call to (*Tx).grabConn. For tests.
+var hookTxGrabConn func()
+
 func (tx *Tx) grabConn(ctx context.Context) (*driverConn, error) {
+	select {
+	default:
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
 	if tx.isDone() {
 		return nil, ErrTxDone
 	}
+	if hookTxGrabConn != nil { // test hook
+		hookTxGrabConn()
+	}
 	return tx.dc, nil
 }
 
@@ -1503,6 +1528,9 @@ func (tx *Tx) Rollback() error {
 // for the execution of the returned statement. The returned statement
 // will run in the transaction context.
 func (tx *Tx) PrepareContext(ctx context.Context, query string) (*Stmt, error) {
+	tx.closemu.RLock()
+	defer tx.closemu.RUnlock()
+
 	// TODO(bradfitz): We could be more efficient here and either
 	// provide a method to take an existing Stmt (created on
 	// perhaps a different Conn), and re-create it on this Conn if
@@ -1567,6 +1595,9 @@ func (tx *Tx) Prepare(query string) (*Stmt, error) {
 // The returned statement operates within the transaction and will be closed
 // when the transaction has been committed or rolled back.
 func (tx *Tx) StmtContext(ctx context.Context, stmt *Stmt) *Stmt {
+	tx.closemu.RLock()
+	defer tx.closemu.RUnlock()
+
 	// TODO(bradfitz): optimize this. Currently this re-prepares
 	// each time. This is fine for now to illustrate the API but
 	// we should really cache already-prepared statements
@@ -1618,6 +1649,9 @@ func (tx *Tx) Stmt(stmt *Stmt) *Stmt {
 // ExecContext executes a query that doesn't return rows.
 // For example: an INSERT and UPDATE.
 func (tx *Tx) ExecContext(ctx context.Context, query string, args ...interface{}) (Result, error) {
+	tx.closemu.RLock()
+	defer tx.closemu.RUnlock()
+
 	dc, err := tx.grabConn(ctx)
 	if err != nil {
 		return nil, err
@@ -1661,6 +1695,9 @@ func (tx *Tx) Exec(query string, args ...interface{}) (Result, error) {
 
 // QueryContext executes a query that returns rows, typically a SELECT.
 func (tx *Tx) QueryContext(ctx context.Context, query string, args ...interface{}) (*Rows, error) {
+	tx.closemu.RLock()
+	defer tx.closemu.RUnlock()
+
 	dc, err := tx.grabConn(ctx)
 	if err != nil {
 		return nil, err
@@ -2038,25 +2075,21 @@ type Rows struct {
 	// closed value is 1 when the Rows is closed.
 	// Use atomic operations on value when checking value.
 	closed    int32
-	ctxClose  chan struct{} // closed when Rows is closed, may be null.
+	cancel    func() // called when Rows is closed, may be nil.
 	lastcols  []driver.Value
 	lasterr   error       // non-nil only if closed is true
 	closeStmt *driverStmt // if non-nil, statement to Close on close
 }
 
 func (rs *Rows) initContextClose(ctx context.Context) {
-	if ctx.Done() == context.Background().Done() {
-		return
-	}
+	ctx, rs.cancel = context.WithCancel(ctx)
+	go rs.awaitDone(ctx)
+}
 
-	rs.ctxClose = make(chan struct{})
-	go func() {
-		select {
-		case <-ctx.Done():
-			rs.Close()
-		case <-rs.ctxClose:
-		}
-	}()
+// awaitDone blocks until the rows are closed or the context canceled.
+func (rs *Rows) awaitDone(ctx context.Context) {
+	<-ctx.Done()
+	rs.Close()
 }
 
 // Next prepares the next result row for reading with the Scan method. It
@@ -2314,7 +2347,9 @@ func (rs *Rows) Scan(dest ...interface{}) error {
 	return nil
 }
 
-var rowsCloseHook func(*Rows, *error)
+// rowsCloseHook returns a function so tests may install the
+// hook throug a test only mutex.
+var rowsCloseHook = func() func(*Rows, *error) { return nil }
 
 func (rs *Rows) isClosed() bool {
 	return atomic.LoadInt32(&rs.closed) != 0
@@ -2328,13 +2363,15 @@ func (rs *Rows) Close() error {
 	if !atomic.CompareAndSwapInt32(&rs.closed, 0, 1) {
 		return nil
 	}
-	if rs.ctxClose != nil {
-		close(rs.ctxClose)
-	}
+
 	err := rs.rowsi.Close()
-	if fn := rowsCloseHook; fn != nil {
+	if fn := rowsCloseHook(); fn != nil {
 		fn(rs, &err)
 	}
+	if rs.cancel != nil {
+		rs.cancel()
+	}
+
 	if rs.closeStmt != nil {
 		rs.closeStmt.Close()
 	}
diff --git a/libgo/go/database/sql/sql_test.go b/libgo/go/database/sql/sql_test.go
index 63e1292..898df3b 100644
--- a/libgo/go/database/sql/sql_test.go
+++ b/libgo/go/database/sql/sql_test.go
@@ -14,6 +14,7 @@ import (
 	"runtime"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"testing"
 	"time"
 )
@@ -326,9 +327,7 @@ func TestQueryContext(t *testing.T) {
 
 	// And verify that the final rows.Next() call, which hit EOF,
 	// also closed the rows connection.
-	if n := db.numFreeConns(); n != 1 {
-		t.Fatalf("free conns after query hitting EOF = %d; want 1", n)
-	}
+	waitForFree(t, db, 5*time.Second, 1)
 	if prepares := numPrepares(t, db) - prepares0; prepares != 1 {
 		t.Errorf("executed %d Prepare statements; want 1", prepares)
 	}
@@ -345,6 +344,18 @@ func waitCondition(waitFor, checkEvery time.Duration, fn func() bool) bool {
 	return false
 }
 
+// waitForFree checks db.numFreeConns until either it equals want or
+// the maxWait time elapses.
+func waitForFree(t *testing.T, db *DB, maxWait time.Duration, want int) {
+	var numFree int
+	if !waitCondition(maxWait, 5*time.Millisecond, func() bool {
+		numFree = db.numFreeConns()
+		return numFree == want
+	}) {
+		t.Fatalf("free conns after hitting EOF = %d; want %d", numFree, want)
+	}
+}
+
 func TestQueryContextWait(t *testing.T) {
 	db := newTestDB(t, "people")
 	defer closeDB(t, db)
@@ -361,9 +372,7 @@ func TestQueryContextWait(t *testing.T) {
 	}
 
 	// Verify closed rows connection after error condition.
-	if n := db.numFreeConns(); n != 1 {
-		t.Fatalf("free conns after query hitting EOF = %d; want 1", n)
-	}
+	waitForFree(t, db, 5*time.Second, 1)
 	if prepares := numPrepares(t, db) - prepares0; prepares != 1 {
 		t.Errorf("executed %d Prepare statements; want 1", prepares)
 	}
@@ -388,13 +397,7 @@ func TestTxContextWait(t *testing.T) {
 		t.Fatalf("expected QueryContext to error with context deadline exceeded but returned %v", err)
 	}
 
-	var numFree int
-	if !waitCondition(5*time.Second, 5*time.Millisecond, func() bool {
-		numFree = db.numFreeConns()
-		return numFree == 0
-	}) {
-		t.Fatalf("free conns after hitting EOF = %d; want 0", numFree)
-	}
+	waitForFree(t, db, 5*time.Second, 0)
 
 	// Ensure the dropped connection allows more connections to be made.
 	// Checked on DB Close.
@@ -471,9 +474,7 @@ func TestMultiResultSetQuery(t *testing.T) {
 
 	// And verify that the final rows.Next() call, which hit EOF,
 	// also closed the rows connection.
-	if n := db.numFreeConns(); n != 1 {
-		t.Fatalf("free conns after query hitting EOF = %d; want 1", n)
-	}
+	waitForFree(t, db, 5*time.Second, 1)
 	if prepares := numPrepares(t, db) - prepares0; prepares != 1 {
 		t.Errorf("executed %d Prepare statements; want 1", prepares)
 	}
@@ -1135,6 +1136,24 @@ func TestQueryRowClosingStmt(t *testing.T) {
 	}
 }
 
+var atomicRowsCloseHook atomic.Value // of func(*Rows, *error)
+
+func init() {
+	rowsCloseHook = func() func(*Rows, *error) {
+		fn, _ := atomicRowsCloseHook.Load().(func(*Rows, *error))
+		return fn
+	}
+}
+
+func setRowsCloseHook(fn func(*Rows, *error)) {
+	if fn == nil {
+		// Can't change an atomic.Value back to nil, so set it to this
+		// no-op func instead.
+		fn = func(*Rows, *error) {}
+	}
+	atomicRowsCloseHook.Store(fn)
+}
+
 // Test issue 6651
 func TestIssue6651(t *testing.T) {
 	db := newTestDB(t, "people")
@@ -1147,6 +1166,7 @@ func TestIssue6651(t *testing.T) {
 		return fmt.Errorf(want)
 	}
 	defer func() { rowsCursorNextHook = nil }()
+
 	err := db.QueryRow("SELECT|people|name|").Scan(&v)
 	if err == nil || err.Error() != want {
 		t.Errorf("error = %q; want %q", err, want)
@@ -1154,10 +1174,10 @@ func TestIssue6651(t *testing.T) {
 	rowsCursorNextHook = nil
 
 	want = "error in rows.Close"
-	rowsCloseHook = func(rows *Rows, err *error) {
+	setRowsCloseHook(func(rows *Rows, err *error) {
 		*err = fmt.Errorf(want)
-	}
-	defer func() { rowsCloseHook = nil }()
+	})
+	defer setRowsCloseHook(nil)
 	err = db.QueryRow("SELECT|people|name|").Scan(&v)
 	if err == nil || err.Error() != want {
 		t.Errorf("error = %q; want %q", err, want)
@@ -1830,7 +1850,9 @@ func TestStmtCloseDeps(t *testing.T) {
 		db.dumpDeps(t)
 	}
 
-	if len(stmt.css) > nquery {
+	if !waitCondition(5*time.Second, 5*time.Millisecond, func() bool {
+		return len(stmt.css) <= nquery
+	}) {
 		t.Errorf("len(stmt.css) = %d; want <= %d", len(stmt.css), nquery)
 	}
 
@@ -2576,10 +2598,10 @@ func TestIssue6081(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	rowsCloseHook = func(rows *Rows, err *error) {
+	setRowsCloseHook(func(rows *Rows, err *error) {
 		*err = driver.ErrBadConn
-	}
-	defer func() { rowsCloseHook = nil }()
+	})
+	defer setRowsCloseHook(nil)
 	for i := 0; i < 10; i++ {
 		rows, err := stmt.Query()
 		if err != nil {
@@ -2642,7 +2664,10 @@ func TestIssue18429(t *testing.T) {
 			if err != nil {
 				return
 			}
-			rows, err := tx.QueryContext(ctx, "WAIT|"+qwait+"|SELECT|people|name|")
+			// This is expected to give a cancel error many, but not all the time.
+			// Test failure will happen with a panic or other race condition being
+			// reported.
+			rows, _ := tx.QueryContext(ctx, "WAIT|"+qwait+"|SELECT|people|name|")
 			if rows != nil {
 				rows.Close()
 			}
@@ -2655,6 +2680,56 @@ func TestIssue18429(t *testing.T) {
 	time.Sleep(milliWait * 3 * time.Millisecond)
 }
 
+// TestIssue18719 closes the context right before use. The sql.driverConn
+// will nil out the ci on close in a lock, but if another process uses it right after
+// it will panic with on the nil ref.
+//
+// See https://golang.org/cl/35550 .
+func TestIssue18719(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	tx, err := db.BeginTx(ctx, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	hookTxGrabConn = func() {
+		cancel()
+
+		// Wait for the context to cancel and tx to rollback.
+		for tx.isDone() == false {
+			time.Sleep(time.Millisecond * 3)
+		}
+	}
+	defer func() { hookTxGrabConn = nil }()
+
+	// This call will grab the connection and cancel the context
+	// after it has done so. Code after must deal with the canceled state.
+	rows, err := tx.QueryContext(ctx, "SELECT|people|name|")
+	if err != nil {
+		rows.Close()
+		t.Fatalf("expected error %v but got %v", nil, err)
+	}
+
+	// Rows may be ignored because it will be closed when the context is canceled.
+
+	// Do not explicitly rollback. The rollback will happen from the
+	// canceled context.
+
+	// Wait for connections to return to pool.
+	var numOpen int
+	if !waitCondition(5*time.Second, 5*time.Millisecond, func() bool {
+		numOpen = db.numOpenConns()
+		return numOpen == 0
+	}) {
+		t.Fatalf("open conns after hitting EOF = %d; want 0", numOpen)
+	}
+}
+
 func TestConcurrency(t *testing.T) {
 	doConcurrentTest(t, new(concurrentDBQueryTest))
 	doConcurrentTest(t, new(concurrentDBExecTest))
diff --git a/libgo/go/go/printer/nodes.go b/libgo/go/go/printer/nodes.go
index 11f26d4..ea43286 100644
--- a/libgo/go/go/printer/nodes.go
+++ b/libgo/go/go/printer/nodes.go
@@ -733,7 +733,7 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int) {
 
 	case *ast.FuncLit:
 		p.expr(x.Type)
-		p.adjBlock(p.distanceFrom(x.Type.Pos()), blank, x.Body)
+		p.funcBody(p.distanceFrom(x.Type.Pos()), blank, x.Body)
 
 	case *ast.ParenExpr:
 		if _, hasParens := x.X.(*ast.ParenExpr); hasParens {
@@ -825,6 +825,7 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int) {
 		if x.Type != nil {
 			p.expr1(x.Type, token.HighestPrec, depth)
 		}
+		p.level++
 		p.print(x.Lbrace, token.LBRACE)
 		p.exprList(x.Lbrace, x.Elts, 1, commaTerm, x.Rbrace)
 		// do not insert extra line break following a /*-style comment
@@ -837,6 +838,7 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int) {
 			mode |= noExtraBlank
 		}
 		p.print(mode, x.Rbrace, token.RBRACE, mode)
+		p.level--
 
 	case *ast.Ellipsis:
 		p.print(token.ELLIPSIS)
@@ -1557,18 +1559,23 @@ func (p *printer) bodySize(b *ast.BlockStmt, maxSize int) int {
 	return bodySize
 }
 
-// adjBlock prints an "adjacent" block (e.g., a for-loop or function body) following
-// a header (e.g., a for-loop control clause or function signature) of given headerSize.
+// funcBody prints a function body following a function header of given headerSize.
 // If the header's and block's size are "small enough" and the block is "simple enough",
 // the block is printed on the current line, without line breaks, spaced from the header
 // by sep. Otherwise the block's opening "{" is printed on the current line, followed by
 // lines for the block's statements and its closing "}".
 //
-func (p *printer) adjBlock(headerSize int, sep whiteSpace, b *ast.BlockStmt) {
+func (p *printer) funcBody(headerSize int, sep whiteSpace, b *ast.BlockStmt) {
 	if b == nil {
 		return
 	}
 
+	// save/restore composite literal nesting level
+	defer func(level int) {
+		p.level = level
+	}(p.level)
+	p.level = 0
+
 	const maxSize = 100
 	if headerSize+p.bodySize(b, maxSize) <= maxSize {
 		p.print(sep, b.Lbrace, token.LBRACE)
@@ -1613,7 +1620,7 @@ func (p *printer) funcDecl(d *ast.FuncDecl) {
 	}
 	p.expr(d.Name)
 	p.signature(d.Type.Params, d.Type.Results)
-	p.adjBlock(p.distanceFrom(d.Pos()), vtab, d.Body)
+	p.funcBody(p.distanceFrom(d.Pos()), vtab, d.Body)
 }
 
 func (p *printer) decl(decl ast.Decl) {
diff --git a/libgo/go/go/printer/printer.go b/libgo/go/go/printer/printer.go
index eabf23e..be61dad5 100644
--- a/libgo/go/go/printer/printer.go
+++ b/libgo/go/go/printer/printer.go
@@ -58,6 +58,7 @@ type printer struct {
 	// Current state
 	output      []byte       // raw printer result
 	indent      int          // current indentation
+	level       int          // level == 0: outside composite literal; level > 0: inside composite literal
 	mode        pmode        // current printer mode
 	impliedSemi bool         // if set, a linebreak implies a semicolon
 	lastTok     token.Token  // last token printed (token.ILLEGAL if it's whitespace)
@@ -744,15 +745,19 @@ func (p *printer) intersperseComments(next token.Position, tok token.Token) (wro
 		// follows on the same line but is not a comma, and not a "closing"
 		// token immediately following its corresponding "opening" token,
 		// add an extra separator unless explicitly disabled. Use a blank
-		// as separator unless we have pending linebreaks and they are not
-		// disabled, in which case we want a linebreak (issue 15137).
+		// as separator unless we have pending linebreaks, they are not
+		// disabled, and we are outside a composite literal, in which case
+		// we want a linebreak (issue 15137).
+		// TODO(gri) This has become overly complicated. We should be able
+		// to track whether we're inside an expression or statement and
+		// use that information to decide more directly.
 		needsLinebreak := false
 		if p.mode&noExtraBlank == 0 &&
 			last.Text[1] == '*' && p.lineFor(last.Pos()) == next.Line &&
 			tok != token.COMMA &&
 			(tok != token.RPAREN || p.prevOpen == token.LPAREN) &&
 			(tok != token.RBRACK || p.prevOpen == token.LBRACK) {
-			if p.containsLinebreak() && p.mode&noExtraLinebreak == 0 {
+			if p.containsLinebreak() && p.mode&noExtraLinebreak == 0 && p.level == 0 {
 				needsLinebreak = true
 			} else {
 				p.writeByte(' ', 1)
diff --git a/libgo/go/go/printer/testdata/comments2.golden b/libgo/go/go/printer/testdata/comments2.golden
index 7676a26..8b3a94d 100644
--- a/libgo/go/go/printer/testdata/comments2.golden
+++ b/libgo/go/go/printer/testdata/comments2.golden
@@ -103,3 +103,62 @@ label:
 	mask := uint64(1)<<c - 1		// Allocation mask
 	used := atomic.LoadUint64(&h.used)	// Current allocations
 }
+
+// Test cases for issue 18782
+var _ = [][]int{
+	/*       a, b, c, d, e */
+	/* a */ {0, 0, 0, 0, 0},
+	/* b */ {0, 5, 4, 4, 4},
+	/* c */ {0, 4, 5, 4, 4},
+	/* d */ {0, 4, 4, 5, 4},
+	/* e */ {0, 4, 4, 4, 5},
+}
+
+var _ = T{ /* a */ 0}
+
+var _ = T{ /* a */ /* b */ 0}
+
+var _ = T{	/* a */	/* b */
+	/* c */ 0,
+}
+
+var _ = T{	/* a */	/* b */
+	/* c */
+	/* d */ 0,
+}
+
+var _ = T{
+	/* a */
+	/* b */ 0,
+}
+
+var _ = T{ /* a */ {}}
+
+var _ = T{ /* a */ /* b */ {}}
+
+var _ = T{	/* a */	/* b */
+	/* c */ {},
+}
+
+var _ = T{	/* a */	/* b */
+	/* c */
+	/* d */ {},
+}
+
+var _ = T{
+	/* a */
+	/* b */ {},
+}
+
+var _ = []T{
+	func() {
+		var _ = [][]int{
+			/*       a, b, c, d, e */
+			/* a */ {0, 0, 0, 0, 0},
+			/* b */ {0, 5, 4, 4, 4},
+			/* c */ {0, 4, 5, 4, 4},
+			/* d */ {0, 4, 4, 5, 4},
+			/* e */ {0, 4, 4, 4, 5},
+		}
+	},
+}
diff --git a/libgo/go/go/printer/testdata/comments2.input b/libgo/go/go/printer/testdata/comments2.input
index 4a055c8..8d38c41 100644
--- a/libgo/go/go/printer/testdata/comments2.input
+++ b/libgo/go/go/printer/testdata/comments2.input
@@ -103,3 +103,66 @@ label:
    mask := uint64(1)<<c - 1 // Allocation mask
    used := atomic.LoadUint64(&h.used) // Current allocations
 }
+
+// Test cases for issue 18782
+var _ = [][]int{
+   /*       a, b, c, d, e */
+   /* a */ {0, 0, 0, 0, 0},
+   /* b */ {0, 5, 4, 4, 4},
+   /* c */ {0, 4, 5, 4, 4},
+   /* d */ {0, 4, 4, 5, 4},
+   /* e */ {0, 4, 4, 4, 5},
+}
+
+var _ = T{ /* a */ 0,
+}
+
+var _ = T{ /* a */ /* b */ 0,
+}
+
+var _ = T{ /* a */ /* b */
+   /* c */ 0,
+}
+
+var _ = T{ /* a */ /* b */
+   /* c */
+   /* d */ 0,
+}
+
+var _ = T{
+   /* a */
+   /* b */ 0,
+}
+
+var _ = T{ /* a */ {},
+}
+
+var _ = T{ /* a */ /* b */ {},
+}
+
+var _ = T{ /* a */ /* b */
+   /* c */ {},
+}
+
+var _ = T{ /* a */ /* b */
+   /* c */
+   /* d */ {},
+}
+
+var _ = T{
+   /* a */
+   /* b */ {},
+}
+
+var _ = []T{
+   func() {
+      var _ = [][]int{
+         /*       a, b, c, d, e */
+         /* a */ {0, 0, 0, 0, 0},
+         /* b */ {0, 5, 4, 4, 4},
+         /* c */ {0, 4, 5, 4, 4},
+         /* d */ {0, 4, 4, 5, 4},
+         /* e */ {0, 4, 4, 4, 5},
+      }
+   },
+}
diff --git a/libgo/go/net/http/client.go b/libgo/go/net/http/client.go
index d368bae..0005538 100644
--- a/libgo/go/net/http/client.go
+++ b/libgo/go/net/http/client.go
@@ -413,11 +413,12 @@ func (c *Client) checkRedirect(req *Request, via []*Request) error {
 
 // redirectBehavior describes what should happen when the
 // client encounters a 3xx status code from the server
-func redirectBehavior(reqMethod string, resp *Response, ireq *Request) (redirectMethod string, shouldRedirect bool) {
+func redirectBehavior(reqMethod string, resp *Response, ireq *Request) (redirectMethod string, shouldRedirect, includeBody bool) {
 	switch resp.StatusCode {
 	case 301, 302, 303:
 		redirectMethod = reqMethod
 		shouldRedirect = true
+		includeBody = false
 
 		// RFC 2616 allowed automatic redirection only with GET and
 		// HEAD requests. RFC 7231 lifts this restriction, but we still
@@ -429,6 +430,7 @@ func redirectBehavior(reqMethod string, resp *Response, ireq *Request) (redirect
 	case 307, 308:
 		redirectMethod = reqMethod
 		shouldRedirect = true
+		includeBody = true
 
 		// Treat 307 and 308 specially, since they're new in
 		// Go 1.8, and they also require re-sending the request body.
@@ -449,7 +451,7 @@ func redirectBehavior(reqMethod string, resp *Response, ireq *Request) (redirect
 			shouldRedirect = false
 		}
 	}
-	return redirectMethod, shouldRedirect
+	return redirectMethod, shouldRedirect, includeBody
 }
 
 // Do sends an HTTP request and returns an HTTP response, following
@@ -492,11 +494,14 @@ func (c *Client) Do(req *Request) (*Response, error) {
 	}
 
 	var (
-		deadline       = c.deadline()
-		reqs           []*Request
-		resp           *Response
-		copyHeaders    = c.makeHeadersCopier(req)
+		deadline    = c.deadline()
+		reqs        []*Request
+		resp        *Response
+		copyHeaders = c.makeHeadersCopier(req)
+
+		// Redirect behavior:
 		redirectMethod string
+		includeBody    bool
 	)
 	uerr := func(err error) error {
 		req.closeBody()
@@ -534,7 +539,7 @@ func (c *Client) Do(req *Request) (*Response, error) {
 				Cancel:   ireq.Cancel,
 				ctx:      ireq.ctx,
 			}
-			if ireq.GetBody != nil {
+			if includeBody && ireq.GetBody != nil {
 				req.Body, err = ireq.GetBody()
 				if err != nil {
 					return nil, uerr(err)
@@ -598,7 +603,7 @@ func (c *Client) Do(req *Request) (*Response, error) {
 		}
 
 		var shouldRedirect bool
-		redirectMethod, shouldRedirect = redirectBehavior(req.Method, resp, reqs[0])
+		redirectMethod, shouldRedirect, includeBody = redirectBehavior(req.Method, resp, reqs[0])
 		if !shouldRedirect {
 			return resp, nil
 		}
diff --git a/libgo/go/net/http/client_test.go b/libgo/go/net/http/client_test.go
index eaf2cdc..4f674dd 100644
--- a/libgo/go/net/http/client_test.go
+++ b/libgo/go/net/http/client_test.go
@@ -360,25 +360,25 @@ func TestPostRedirects(t *testing.T) {
 	wantSegments := []string{
 		`POST / "first"`,
 		`POST /?code=301&next=302 "c301"`,
-		`GET /?code=302 "c301"`,
-		`GET / "c301"`,
+		`GET /?code=302 ""`,
+		`GET / ""`,
 		`POST /?code=302&next=302 "c302"`,
-		`GET /?code=302 "c302"`,
-		`GET / "c302"`,
+		`GET /?code=302 ""`,
+		`GET / ""`,
 		`POST /?code=303&next=301 "c303wc301"`,
-		`GET /?code=301 "c303wc301"`,
-		`GET / "c303wc301"`,
+		`GET /?code=301 ""`,
+		`GET / ""`,
 		`POST /?code=304 "c304"`,
 		`POST /?code=305 "c305"`,
 		`POST /?code=307&next=303,308,302 "c307"`,
 		`POST /?code=303&next=308,302 "c307"`,
-		`GET /?code=308&next=302 "c307"`,
+		`GET /?code=308&next=302 ""`,
 		`GET /?code=302 "c307"`,
-		`GET / "c307"`,
+		`GET / ""`,
 		`POST /?code=308&next=302,301 "c308"`,
 		`POST /?code=302&next=301 "c308"`,
-		`GET /?code=301 "c308"`,
-		`GET / "c308"`,
+		`GET /?code=301 ""`,
+		`GET / ""`,
 		`POST /?code=404 "c404"`,
 	}
 	want := strings.Join(wantSegments, "\n")
@@ -399,20 +399,20 @@ func TestDeleteRedirects(t *testing.T) {
 	wantSegments := []string{
 		`DELETE / "first"`,
 		`DELETE /?code=301&next=302,308 "c301"`,
-		`GET /?code=302&next=308 "c301"`,
-		`GET /?code=308 "c301"`,
+		`GET /?code=302&next=308 ""`,
+		`GET /?code=308 ""`,
 		`GET / "c301"`,
 		`DELETE /?code=302&next=302 "c302"`,
-		`GET /?code=302 "c302"`,
-		`GET / "c302"`,
+		`GET /?code=302 ""`,
+		`GET / ""`,
 		`DELETE /?code=303 "c303"`,
-		`GET / "c303"`,
+		`GET / ""`,
 		`DELETE /?code=307&next=301,308,303,302,304 "c307"`,
 		`DELETE /?code=301&next=308,303,302,304 "c307"`,
-		`GET /?code=308&next=303,302,304 "c307"`,
+		`GET /?code=308&next=303,302,304 ""`,
 		`GET /?code=303&next=302,304 "c307"`,
-		`GET /?code=302&next=304 "c307"`,
-		`GET /?code=304 "c307"`,
+		`GET /?code=302&next=304 ""`,
+		`GET /?code=304 ""`,
 		`DELETE /?code=308&next=307 "c308"`,
 		`DELETE /?code=307 "c308"`,
 		`DELETE / "c308"`,
@@ -432,7 +432,11 @@ func testRedirectsByMethod(t *testing.T, method string, table []redirectTest, wa
 	ts = httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		log.Lock()
 		slurp, _ := ioutil.ReadAll(r.Body)
-		fmt.Fprintf(&log.Buffer, "%s %s %q\n", r.Method, r.RequestURI, slurp)
+		fmt.Fprintf(&log.Buffer, "%s %s %q", r.Method, r.RequestURI, slurp)
+		if cl := r.Header.Get("Content-Length"); r.Method == "GET" && len(slurp) == 0 && (r.ContentLength != 0 || cl != "") {
+			fmt.Fprintf(&log.Buffer, " (but with body=%T, content-length = %v, %q)", r.Body, r.ContentLength, cl)
+		}
+		log.WriteByte('\n')
 		log.Unlock()
 		urlQuery := r.URL.Query()
 		if v := urlQuery.Get("code"); v != "" {
@@ -475,7 +479,24 @@ func testRedirectsByMethod(t *testing.T, method string, table []redirectTest, wa
 	want = strings.TrimSpace(want)
 
 	if got != want {
-		t.Errorf("Log differs.\n Got:\n%s\nWant:\n%s\n", got, want)
+		got, want, lines := removeCommonLines(got, want)
+		t.Errorf("Log differs after %d common lines.\n\nGot:\n%s\n\nWant:\n%s\n", lines, got, want)
+	}
+}
+
+func removeCommonLines(a, b string) (asuffix, bsuffix string, commonLines int) {
+	for {
+		nl := strings.IndexByte(a, '\n')
+		if nl < 0 {
+			return a, b, commonLines
+		}
+		line := a[:nl+1]
+		if !strings.HasPrefix(b, line) {
+			return a, b, commonLines
+		}
+		commonLines++
+		a = a[len(line):]
+		b = b[len(line):]
 	}
 }
 
diff --git a/libgo/go/net/http/serve_test.go b/libgo/go/net/http/serve_test.go
index 681dff1..73dd56e 100644
--- a/libgo/go/net/http/serve_test.go
+++ b/libgo/go/net/http/serve_test.go
@@ -5277,7 +5277,7 @@ func TestServerHijackGetsBackgroundByte_big(t *testing.T) {
 		defer conn.Close()
 		slurp, err := ioutil.ReadAll(buf.Reader)
 		if err != nil {
-			t.Error("Copy: %v", err)
+			t.Errorf("Copy: %v", err)
 		}
 		allX := true
 		for _, v := range slurp {
diff --git a/libgo/merge.sh b/libgo/merge.sh
index c750a5d..bdf0043 100755
--- a/libgo/merge.sh
+++ b/libgo/merge.sh
@@ -71,7 +71,9 @@ merge() {
   elif test -f ${old}; then
     # The file exists in the old version.
     if ! test -f ${libgo}; then
-      echo "merge.sh: $name: skipping: exists in old and new git, but not in libgo"
+      if ! cmp -s ${old} ${new}; then
+        echo "merge.sh: $name: skipping: exists in old and new git, but not in libgo"
+      fi
       continue
     fi
     if cmp -s ${old} ${libgo}; then