diff --git a/pkg/golinters/goanalysis/analysisflags/flags.go b/pkg/golinters/goanalysis/analysisflags/flags.go
new file mode 100644
index 00000000..a03a185f
--- /dev/null
+++ b/pkg/golinters/goanalysis/analysisflags/flags.go
@@ -0,0 +1,344 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package analysisflags defines helpers for processing flags of
+// analysis driver tools.
+package analysisflags
+
+import (
+	"crypto/sha256"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"go/token"
+	"io"
+	"io/ioutil"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+// flags common to all {single,multi,unit}checkers.
+var (
+	JSON    = false // -json
+	Context = -1    // -c=N: if N>0, display offending line plus N lines of context
+)
+
+// Parse creates a flag for each of the analyzer's flags,
+// including (in multi mode) a flag named after the analyzer,
+// parses the flags, then filters and returns the list of
+// analyzers enabled by flags.
+func Parse(analyzers []*analysis.Analyzer, multi bool) []*analysis.Analyzer {
+	// Connect each analysis flag to the command line as -analysis.flag.
+	enabled := make(map[*analysis.Analyzer]*triState)
+	for _, a := range analyzers {
+		var prefix string
+
+		// Add -NAME flag to enable it.
+		if multi {
+			prefix = a.Name + "."
+
+			enable := new(triState)
+			enableUsage := "enable " + a.Name + " analysis"
+			flag.Var(enable, a.Name, enableUsage)
+			enabled[a] = enable
+		}
+
+		a.Flags.VisitAll(func(f *flag.Flag) {
+			if !multi && flag.Lookup(f.Name) != nil {
+				log.Printf("%s flag -%s would conflict with driver; skipping", a.Name, f.Name)
+				return
+			}
+
+			name := prefix + f.Name
+			flag.Var(f.Value, name, f.Usage)
+		})
+	}
+
+	// standard flags: -flags, -V.
+	printflags := flag.Bool("flags", false, "print analyzer flags in JSON")
+	addVersionFlag()
+
+	// flags common to all checkers
+	flag.BoolVar(&JSON, "json", JSON, "emit JSON output")
+	flag.IntVar(&Context, "c", Context, `display offending line with this many lines of context`)
+
+	// Add shims for legacy vet flags to enable existing
+	// scripts that run vet to continue to work.
+	_ = flag.Bool("source", false, "no effect (deprecated)")
+	_ = flag.Bool("v", false, "no effect (deprecated)")
+	_ = flag.Bool("all", false, "no effect (deprecated)")
+	_ = flag.String("tags", "", "no effect (deprecated)")
+	for old, new := range vetLegacyFlags {
+		newFlag := flag.Lookup(new)
+		if newFlag != nil && flag.Lookup(old) == nil {
+			flag.Var(newFlag.Value, old, "deprecated alias for -"+new)
+		}
+	}
+
+	flag.Parse() // (ExitOnError)
+
+	// -flags: print flags so that go vet knows which ones are legitimate.
+	if *printflags {
+		printFlags()
+		os.Exit(0)
+	}
+
+	// If any -NAME flag is true,  run only those analyzers. Otherwise,
+	// if any -NAME flag is false, run all but those analyzers.
+	if multi {
+		var hasTrue, hasFalse bool
+		for _, ts := range enabled {
+			switch *ts {
+			case setTrue:
+				hasTrue = true
+			case setFalse:
+				hasFalse = true
+			}
+		}
+
+		var keep []*analysis.Analyzer
+		if hasTrue {
+			for _, a := range analyzers {
+				if *enabled[a] == setTrue {
+					keep = append(keep, a)
+				}
+			}
+			analyzers = keep
+		} else if hasFalse {
+			for _, a := range analyzers {
+				if *enabled[a] != setFalse {
+					keep = append(keep, a)
+				}
+			}
+			analyzers = keep
+		}
+	}
+
+	return analyzers
+}
+
+func printFlags() {
+	type jsonFlag struct {
+		Name  string
+		Bool  bool
+		Usage string
+	}
+	var flags []jsonFlag = nil
+	flag.VisitAll(func(f *flag.Flag) {
+		// Don't report {single,multi}checker debugging
+		// flags as these have no effect on unitchecker
+		// (as invoked by 'go vet').
+		switch f.Name {
+		case "debug", "cpuprofile", "memprofile", "trace":
+			return
+		}
+
+		b, ok := f.Value.(interface{ IsBoolFlag() bool })
+		isBool := ok && b.IsBoolFlag()
+		flags = append(flags, jsonFlag{f.Name, isBool, f.Usage})
+	})
+	data, err := json.MarshalIndent(flags, "", "\t")
+	if err != nil {
+		log.Fatal(err)
+	}
+	os.Stdout.Write(data)
+}
+
+// addVersionFlag registers a -V flag that, if set,
+// prints the executable version and exits 0.
+//
+// If the -V flag already exists — for example, because it was already
+// registered by a call to cmd/internal/objabi.AddVersionFlag — then
+// addVersionFlag does nothing.
+func addVersionFlag() {
+	if flag.Lookup("V") == nil {
+		flag.Var(versionFlag{}, "V", "print version and exit")
+	}
+}
+
+// versionFlag minimally complies with the -V protocol required by "go vet".
+type versionFlag struct{}
+
+func (versionFlag) IsBoolFlag() bool { return true }
+func (versionFlag) Get() interface{} { return nil }
+func (versionFlag) String() string   { return "" }
+func (versionFlag) Set(s string) error {
+	if s != "full" {
+		log.Fatalf("unsupported flag value: -V=%s", s)
+	}
+
+	// This replicates the miminal subset of
+	// cmd/internal/objabi.AddVersionFlag, which is private to the
+	// go tool yet forms part of our command-line interface.
+	// TODO(adonovan): clarify the contract.
+
+	// Print the tool version so the build system can track changes.
+	// Formats:
+	//   $progname version devel ... buildID=...
+	//   $progname version go1.9.1
+	progname := os.Args[0]
+	f, err := os.Open(progname)
+	if err != nil {
+		log.Fatal(err)
+	}
+	h := sha256.New()
+	if _, err := io.Copy(h, f); err != nil {
+		log.Fatal(err)
+	}
+	f.Close()
+	fmt.Printf("%s version devel comments-go-here buildID=%02x\n",
+		progname, string(h.Sum(nil)))
+	os.Exit(0)
+	return nil
+}
+
+// A triState is a boolean that knows whether
+// it has been set to either true or false.
+// It is used to identify whether a flag appears;
+// the standard boolean flag cannot
+// distinguish missing from unset.
+// It also satisfies flag.Value.
+type triState int
+
+const (
+	unset triState = iota
+	setTrue
+	setFalse
+)
+
+func triStateFlag(name string, value triState, usage string) *triState {
+	flag.Var(&value, name, usage)
+	return &value
+}
+
+// triState implements flag.Value, flag.Getter, and flag.boolFlag.
+// They work like boolean flags: we can say vet -printf as well as vet -printf=true
+func (ts *triState) Get() interface{} {
+	return *ts == setTrue
+}
+
+func (ts triState) isTrue() bool {
+	return ts == setTrue
+}
+
+func (ts *triState) Set(value string) error {
+	b, err := strconv.ParseBool(value)
+	if err != nil {
+		// This error message looks poor but package "flag" adds
+		// "invalid boolean value %q for -NAME: %s"
+		return fmt.Errorf("want true or false")
+	}
+	if b {
+		*ts = setTrue
+	} else {
+		*ts = setFalse
+	}
+	return nil
+}
+
+func (ts *triState) String() string {
+	switch *ts {
+	case unset:
+		return "true"
+	case setTrue:
+		return "true"
+	case setFalse:
+		return "false"
+	}
+	panic("not reached")
+}
+
+func (ts triState) IsBoolFlag() bool {
+	return true
+}
+
+// Legacy flag support
+
+// vetLegacyFlags maps flags used by legacy vet to their corresponding
+// new names. The old names will continue to work.
+var vetLegacyFlags = map[string]string{
+	// Analyzer name changes
+	"bool":       "bools",
+	"buildtags":  "buildtag",
+	"methods":    "stdmethods",
+	"rangeloops": "loopclosure",
+
+	// Analyzer flags
+	"compositewhitelist":  "composites.whitelist",
+	"printfuncs":          "printf.funcs",
+	"shadowstrict":        "shadow.strict",
+	"unusedfuncs":         "unusedresult.funcs",
+	"unusedstringmethods": "unusedresult.stringmethods",
+}
+
+// ---- output helpers common to all drivers ----
+
+// PrintPlain prints a diagnostic in plain text form,
+// with context specified by the -c flag.
+func PrintPlain(fset *token.FileSet, diag analysis.Diagnostic) {
+	posn := fset.Position(diag.Pos)
+	fmt.Fprintf(os.Stderr, "%s: %s\n", posn, diag.Message)
+
+	// -c=N: show offending line plus N lines of context.
+	if Context >= 0 {
+		data, _ := ioutil.ReadFile(posn.Filename)
+		lines := strings.Split(string(data), "\n")
+		for i := posn.Line - Context; i <= posn.Line+Context; i++ {
+			if 1 <= i && i <= len(lines) {
+				fmt.Fprintf(os.Stderr, "%d\t%s\n", i, lines[i-1])
+			}
+		}
+	}
+}
+
+// A JSONTree is a mapping from package ID to analysis name to result.
+// Each result is either a jsonError or a list of jsonDiagnostic.
+type JSONTree map[string]map[string]interface{}
+
+// Add adds the result of analysis 'name' on package 'id'.
+// The result is either a list of diagnostics or an error.
+func (tree JSONTree) Add(fset *token.FileSet, id, name string, diags []analysis.Diagnostic, err error) {
+	var v interface{}
+	if err != nil {
+		type jsonError struct {
+			Err string `json:"error"`
+		}
+		v = jsonError{err.Error()}
+	} else if len(diags) > 0 {
+		type jsonDiagnostic struct {
+			Category string `json:"category,omitempty"`
+			Posn     string `json:"posn"`
+			Message  string `json:"message"`
+		}
+		var diagnostics []jsonDiagnostic
+		for _, f := range diags {
+			diagnostics = append(diagnostics, jsonDiagnostic{
+				Category: f.Category,
+				Posn:     fset.Position(f.Pos).String(),
+				Message:  f.Message,
+			})
+		}
+		v = diagnostics
+	}
+	if v != nil {
+		m, ok := tree[id]
+		if !ok {
+			m = make(map[string]interface{})
+			tree[id] = m
+		}
+		m[name] = v
+	}
+}
+
+func (tree JSONTree) Print() {
+	data, err := json.MarshalIndent(tree, "", "\t")
+	if err != nil {
+		log.Panicf("internal error: JSON marshalling failed: %v", err)
+	}
+	fmt.Printf("%s\n", data)
+}
diff --git a/pkg/golinters/goanalysis/checker/checker.go b/pkg/golinters/goanalysis/checker/checker.go
new file mode 100644
index 00000000..ec80606a
--- /dev/null
+++ b/pkg/golinters/goanalysis/checker/checker.go
@@ -0,0 +1,708 @@
+// checker is a partial copy of https://github.com/golang/tools/blob/master/go/analysis/internal/checker
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package checker defines the implementation of the checker commands.
+// The same code drives the multi-analysis driver, the single-analysis
+// driver that is conventionally provided for convenience along with
+// each analysis package, and the test driver.
+package checker
+
+import (
+	"bytes"
+	"encoding/gob"
+	"flag"
+	"fmt"
+	"go/token"
+	"go/types"
+	"log"
+	"os"
+	"reflect"
+	"runtime"
+	"runtime/pprof"
+	"runtime/trace"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/packages"
+
+	"github.com/golangci/golangci-lint/pkg/golinters/goanalysis/analysisflags"
+)
+
+var (
+	// Debug is a set of single-letter flags:
+	//
+	//	f	show [f]acts as they are created
+	// 	p	disable [p]arallel execution of analyzers
+	//	s	do additional [s]anity checks on fact types and serialization
+	//	t	show [t]iming info (NB: use 'p' flag to avoid GC/scheduler noise)
+	//	v	show [v]erbose logging
+	//
+	Debug = ""
+
+	// Log files for optional performance tracing.
+	CPUProfile, MemProfile, Trace string
+)
+
+// RegisterFlags registers command-line flags used by the analysis driver.
+func RegisterFlags() {
+	// When adding flags here, remember to update
+	// the list of suppressed flags in analysisflags.
+
+	flag.StringVar(&Debug, "debug", Debug, `debug flags, any subset of "fpstv"`)
+
+	flag.StringVar(&CPUProfile, "cpuprofile", "", "write CPU profile to this file")
+	flag.StringVar(&MemProfile, "memprofile", "", "write memory profile to this file")
+	flag.StringVar(&Trace, "trace", "", "write trace log to this file")
+}
+
+// Run loads the packages specified by args using go/packages,
+// then applies the specified analyzers to them.
+// Analysis flags must already have been set.
+// It provides most of the logic for the main functions of both the
+// singlechecker and the multi-analysis commands.
+// It returns the appropriate exit code.
+func Run(args []string, analyzers []*analysis.Analyzer) (exitcode int) {
+	if CPUProfile != "" {
+		f, err := os.Create(CPUProfile)
+		if err != nil {
+			log.Fatal(err)
+		}
+		if err := pprof.StartCPUProfile(f); err != nil {
+			log.Fatal(err)
+		}
+		// NB: profile won't be written in case of error.
+		defer pprof.StopCPUProfile()
+	}
+
+	if Trace != "" {
+		f, err := os.Create(Trace)
+		if err != nil {
+			log.Fatal(err)
+		}
+		if err := trace.Start(f); err != nil {
+			log.Fatal(err)
+		}
+		// NB: trace log won't be written in case of error.
+		defer func() {
+			trace.Stop()
+			log.Printf("To view the trace, run:\n$ go tool trace view %s", Trace)
+		}()
+	}
+
+	if MemProfile != "" {
+		f, err := os.Create(MemProfile)
+		if err != nil {
+			log.Fatal(err)
+		}
+		// NB: memprofile won't be written in case of error.
+		defer func() {
+			runtime.GC() // get up-to-date statistics
+			if err := pprof.WriteHeapProfile(f); err != nil {
+				log.Fatalf("Writing memory profile: %v", err)
+			}
+			f.Close()
+		}()
+	}
+
+	// Load the packages.
+	if dbg('v') {
+		log.SetPrefix("")
+		log.SetFlags(log.Lmicroseconds) // display timing
+		log.Printf("load %s", args)
+	}
+
+	// Optimization: if the selected analyzers don't produce/consume
+	// facts, we need source only for the initial packages.
+	allSyntax := needFacts(analyzers)
+	initial, err := load(args, allSyntax)
+	if err != nil {
+		log.Print(err)
+		return 1 // load errors
+	}
+
+	// Print the results.
+	roots := analyze(initial, analyzers)
+
+	return printDiagnostics(roots)
+}
+
+// load loads the initial packages.
+func load(patterns []string, allSyntax bool) ([]*packages.Package, error) {
+	mode := packages.LoadSyntax
+	if allSyntax {
+		mode = packages.LoadAllSyntax
+	}
+	conf := packages.Config{
+		Mode:  mode,
+		Tests: true,
+	}
+	initial, err := packages.Load(&conf, patterns...)
+	if err == nil {
+		if n := packages.PrintErrors(initial); n > 1 {
+			err = fmt.Errorf("%d errors during loading", n)
+		} else if n == 1 {
+			err = fmt.Errorf("error during loading")
+		} else if len(initial) == 0 {
+			err = fmt.Errorf("%s matched no packages", strings.Join(patterns, " "))
+		}
+	}
+
+	return initial, err
+}
+
+// TestAnalyzer applies an analysis to a set of packages (and their
+// dependencies if necessary) and returns the results.
+//
+// Facts about pkg are returned in a map keyed by object; package facts
+// have a nil key.
+//
+// This entry point is used only by analysistest.
+func TestAnalyzer(a *analysis.Analyzer, pkgs []*packages.Package) []*TestAnalyzerResult {
+	var results []*TestAnalyzerResult
+	for _, act := range analyze(pkgs, []*analysis.Analyzer{a}) {
+		facts := make(map[types.Object][]analysis.Fact)
+		for key, fact := range act.objectFacts {
+			if key.obj.Pkg() == act.pass.Pkg {
+				facts[key.obj] = append(facts[key.obj], fact)
+			}
+		}
+		for key, fact := range act.packageFacts {
+			if key.pkg == act.pass.Pkg {
+				facts[nil] = append(facts[nil], fact)
+			}
+		}
+
+		results = append(results, &TestAnalyzerResult{act.pass, act.diagnostics, facts, act.result, act.err})
+	}
+	return results
+}
+
+type TestAnalyzerResult struct {
+	Pass        *analysis.Pass
+	Diagnostics []analysis.Diagnostic
+	Facts       map[types.Object][]analysis.Fact
+	Result      interface{}
+	Err         error
+}
+
+func analyze(pkgs []*packages.Package, analyzers []*analysis.Analyzer) []*action {
+	// Construct the action graph.
+	if dbg('v') {
+		log.Printf("building graph of analysis passes")
+	}
+
+	// Each graph node (action) is one unit of analysis.
+	// Edges express package-to-package (vertical) dependencies,
+	// and analysis-to-analysis (horizontal) dependencies.
+	type key struct {
+		*analysis.Analyzer
+		*packages.Package
+	}
+	actions := make(map[key]*action)
+
+	var mkAction func(a *analysis.Analyzer, pkg *packages.Package) *action
+	mkAction = func(a *analysis.Analyzer, pkg *packages.Package) *action {
+		k := key{a, pkg}
+		act, ok := actions[k]
+		if !ok {
+			act = &action{a: a, pkg: pkg}
+
+			// Add a dependency on each required analyzers.
+			for _, req := range a.Requires {
+				act.deps = append(act.deps, mkAction(req, pkg))
+			}
+
+			// An analysis that consumes/produces facts
+			// must run on the package's dependencies too.
+			if len(a.FactTypes) > 0 {
+				paths := make([]string, 0, len(pkg.Imports))
+				for path := range pkg.Imports {
+					paths = append(paths, path)
+				}
+				sort.Strings(paths) // for determinism
+				for _, path := range paths {
+					dep := mkAction(a, pkg.Imports[path])
+					act.deps = append(act.deps, dep)
+				}
+			}
+
+			actions[k] = act
+		}
+		return act
+	}
+
+	// Build nodes for initial packages.
+	var roots []*action
+	for _, a := range analyzers {
+		for _, pkg := range pkgs {
+			root := mkAction(a, pkg)
+			root.isroot = true
+			roots = append(roots, root)
+		}
+	}
+
+	// Execute the graph in parallel.
+	execAll(roots)
+
+	return roots
+}
+
+// printDiagnostics prints the diagnostics for the root packages in either
+// plain text or JSON format. JSON format also includes errors for any
+// dependencies.
+//
+// It returns the exitcode: in plain mode, 0 for success, 1 for analysis
+// errors, and 3 for diagnostics. We avoid 2 since the flag package uses
+// it. JSON mode always succeeds at printing errors and diagnostics in a
+// structured form to stdout.
+func printDiagnostics(roots []*action) (exitcode int) {
+	// Print the output.
+	//
+	// Print diagnostics only for root packages,
+	// but errors for all packages.
+	printed := make(map[*action]bool)
+	var print func(*action)
+	var visitAll func(actions []*action)
+	visitAll = func(actions []*action) {
+		for _, act := range actions {
+			if !printed[act] {
+				printed[act] = true
+				visitAll(act.deps)
+				print(act)
+			}
+		}
+	}
+
+	if analysisflags.JSON {
+		// JSON output
+		tree := make(analysisflags.JSONTree)
+		print = func(act *action) {
+			var diags []analysis.Diagnostic
+			if act.isroot {
+				diags = act.diagnostics
+			}
+			tree.Add(act.pkg.Fset, act.pkg.ID, act.a.Name, diags, act.err)
+		}
+		visitAll(roots)
+		tree.Print()
+	} else {
+		// plain text output
+
+		// De-duplicate diagnostics by position (not token.Pos) to
+		// avoid double-reporting in source files that belong to
+		// multiple packages, such as foo and foo.test.
+		type key struct {
+			token.Position
+			*analysis.Analyzer
+			message string
+		}
+		seen := make(map[key]bool)
+
+		print = func(act *action) {
+			if act.err != nil {
+				fmt.Fprintf(os.Stderr, "%s: %v\n", act.a.Name, act.err)
+				exitcode = 1 // analysis failed, at least partially
+				return
+			}
+			if act.isroot {
+				for _, diag := range act.diagnostics {
+					// We don't display a.Name/f.Category
+					// as most users don't care.
+
+					posn := act.pkg.Fset.Position(diag.Pos)
+					k := key{posn, act.a, diag.Message}
+					if seen[k] {
+						continue // duplicate
+					}
+					seen[k] = true
+
+					analysisflags.PrintPlain(act.pkg.Fset, diag)
+				}
+			}
+		}
+		visitAll(roots)
+
+		if exitcode == 0 && len(seen) > 0 {
+			exitcode = 3 // successfuly produced diagnostics
+		}
+	}
+
+	// Print timing info.
+	if dbg('t') {
+		if !dbg('p') {
+			log.Println("Warning: times are mostly GC/scheduler noise; use -debug=tp to disable parallelism")
+		}
+		var all []*action
+		var total time.Duration
+		for act := range printed {
+			all = append(all, act)
+			total += act.duration
+		}
+		sort.Slice(all, func(i, j int) bool {
+			return all[i].duration > all[j].duration
+		})
+
+		// Print actions accounting for 90% of the total.
+		var sum time.Duration
+		for _, act := range all {
+			fmt.Fprintf(os.Stderr, "%s\t%s\n", act.duration, act)
+			sum += act.duration
+			if sum >= total*9/10 {
+				break
+			}
+		}
+	}
+
+	return exitcode
+}
+
+// needFacts reports whether any analysis required by the specified set
+// needs facts.  If so, we must load the entire program from source.
+func needFacts(analyzers []*analysis.Analyzer) bool {
+	seen := make(map[*analysis.Analyzer]bool)
+	var q []*analysis.Analyzer // for BFS
+	q = append(q, analyzers...)
+	for len(q) > 0 {
+		a := q[0]
+		q = q[1:]
+		if !seen[a] {
+			seen[a] = true
+			if len(a.FactTypes) > 0 {
+				return true
+			}
+			q = append(q, a.Requires...)
+		}
+	}
+	return false
+}
+
+// An action represents one unit of analysis work: the application of
+// one analysis to one package. Actions form a DAG, both within a
+// package (as different analyzers are applied, either in sequence or
+// parallel), and across packages (as dependencies are analyzed).
+type action struct {
+	once         sync.Once
+	a            *analysis.Analyzer
+	pkg          *packages.Package
+	pass         *analysis.Pass
+	isroot       bool
+	deps         []*action
+	objectFacts  map[objectFactKey]analysis.Fact
+	packageFacts map[packageFactKey]analysis.Fact
+	inputs       map[*analysis.Analyzer]interface{}
+	result       interface{}
+	diagnostics  []analysis.Diagnostic
+	err          error
+	duration     time.Duration
+}
+
+type objectFactKey struct {
+	obj types.Object
+	typ reflect.Type
+}
+
+type packageFactKey struct {
+	pkg *types.Package
+	typ reflect.Type
+}
+
+func (act *action) String() string {
+	return fmt.Sprintf("%s@%s", act.a, act.pkg)
+}
+
+func execAll(actions []*action) {
+	sequential := dbg('p')
+	var wg sync.WaitGroup
+	for _, act := range actions {
+		wg.Add(1)
+		work := func(act *action) {
+			act.exec()
+			wg.Done()
+		}
+		if sequential {
+			work(act)
+		} else {
+			go work(act)
+		}
+	}
+	wg.Wait()
+}
+
+func (act *action) exec() { act.once.Do(act.execOnce) }
+
+func (act *action) execOnce() {
+	// Analyze dependencies.
+	execAll(act.deps)
+
+	// TODO(adonovan): uncomment this during profiling.
+	// It won't build pre-go1.11 but conditional compilation
+	// using build tags isn't warranted.
+	//
+	// ctx, task := trace.NewTask(context.Background(), "exec")
+	// trace.Log(ctx, "pass", act.String())
+	// defer task.End()
+
+	// Record time spent in this node but not its dependencies.
+	// In parallel mode, due to GC/scheduler contention, the
+	// time is 5x higher than in sequential mode, even with a
+	// semaphore limiting the number of threads here.
+	// So use -debug=tp.
+	if dbg('t') {
+		t0 := time.Now()
+		defer func() { act.duration = time.Since(t0) }()
+	}
+
+	// Report an error if any dependency failed.
+	var failed []string
+	for _, dep := range act.deps {
+		if dep.err != nil {
+			failed = append(failed, dep.String())
+		}
+	}
+	if failed != nil {
+		sort.Strings(failed)
+		act.err = fmt.Errorf("failed prerequisites: %s", strings.Join(failed, ", "))
+		return
+	}
+
+	// Plumb the output values of the dependencies
+	// into the inputs of this action.  Also facts.
+	inputs := make(map[*analysis.Analyzer]interface{})
+	act.objectFacts = make(map[objectFactKey]analysis.Fact)
+	act.packageFacts = make(map[packageFactKey]analysis.Fact)
+	for _, dep := range act.deps {
+		if dep.pkg == act.pkg {
+			// Same package, different analysis (horizontal edge):
+			// in-memory outputs of prerequisite analyzers
+			// become inputs to this analysis pass.
+			inputs[dep.a] = dep.result
+
+		} else if dep.a == act.a { // (always true)
+			// Same analysis, different package (vertical edge):
+			// serialized facts produced by prerequisite analysis
+			// become available to this analysis pass.
+			inheritFacts(act, dep)
+		}
+	}
+
+	// Run the analysis.
+	pass := &analysis.Pass{
+		Analyzer:          act.a,
+		Fset:              act.pkg.Fset,
+		Files:             act.pkg.Syntax,
+		OtherFiles:        act.pkg.OtherFiles,
+		Pkg:               act.pkg.Types,
+		TypesInfo:         act.pkg.TypesInfo,
+		TypesSizes:        act.pkg.TypesSizes,
+		ResultOf:          inputs,
+		Report:            func(d analysis.Diagnostic) { act.diagnostics = append(act.diagnostics, d) },
+		ImportObjectFact:  act.importObjectFact,
+		ExportObjectFact:  act.exportObjectFact,
+		ImportPackageFact: act.importPackageFact,
+		ExportPackageFact: act.exportPackageFact,
+	}
+	act.pass = pass
+
+	var err error
+	if act.pkg.IllTyped && !pass.Analyzer.RunDespiteErrors {
+		err = fmt.Errorf("analysis skipped due to errors in package")
+	} else {
+		act.result, err = pass.Analyzer.Run(pass)
+		if err == nil {
+			if got, want := reflect.TypeOf(act.result), pass.Analyzer.ResultType; got != want {
+				err = fmt.Errorf(
+					"internal error: on package %s, analyzer %s returned a result of type %v, but declared ResultType %v",
+					pass.Pkg.Path(), pass.Analyzer, got, want)
+			}
+		}
+	}
+	act.err = err
+
+	// disallow calls after Run
+	pass.ExportObjectFact = nil
+	pass.ExportPackageFact = nil
+}
+
+// inheritFacts populates act.facts with
+// those it obtains from its dependency, dep.
+func inheritFacts(act, dep *action) {
+	serialize := dbg('s')
+
+	for key, fact := range dep.objectFacts {
+		// Filter out facts related to objects
+		// that are irrelevant downstream
+		// (equivalently: not in the compiler export data).
+		if !exportedFrom(key.obj, dep.pkg.Types) {
+			if false {
+				log.Printf("%v: discarding %T fact from %s for %s: %s", act, fact, dep, key.obj, fact)
+			}
+			continue
+		}
+
+		// Optionally serialize/deserialize fact
+		// to verify that it works across address spaces.
+		if serialize {
+			var err error
+			fact, err = codeFact(fact)
+			if err != nil {
+				log.Panicf("internal error: encoding of %T fact failed in %v", fact, act)
+			}
+		}
+
+		if false {
+			log.Printf("%v: inherited %T fact for %s: %s", act, fact, key.obj, fact)
+		}
+		act.objectFacts[key] = fact
+	}
+
+	for key, fact := range dep.packageFacts {
+		// TODO: filter out facts that belong to
+		// packages not mentioned in the export data
+		// to prevent side channels.
+
+		// Optionally serialize/deserialize fact
+		// to verify that it works across address spaces
+		// and is deterministic.
+		if serialize {
+			var err error
+			fact, err = codeFact(fact)
+			if err != nil {
+				log.Panicf("internal error: encoding of %T fact failed in %v", fact, act)
+			}
+		}
+
+		if false {
+			log.Printf("%v: inherited %T fact for %s: %s", act, fact, key.pkg.Path(), fact)
+		}
+		act.packageFacts[key] = fact
+	}
+}
+
+// codeFact encodes then decodes a fact,
+// just to exercise that logic.
+func codeFact(fact analysis.Fact) (analysis.Fact, error) {
+	// We encode facts one at a time.
+	// A real modular driver would emit all facts
+	// into one encoder to improve gob efficiency.
+	var buf bytes.Buffer
+	if err := gob.NewEncoder(&buf).Encode(fact); err != nil {
+		return nil, err
+	}
+
+	// Encode it twice and assert that we get the same bits.
+	// This helps detect nondeterministic Gob encoding (e.g. of maps).
+	var buf2 bytes.Buffer
+	if err := gob.NewEncoder(&buf2).Encode(fact); err != nil {
+		return nil, err
+	}
+	if !bytes.Equal(buf.Bytes(), buf2.Bytes()) {
+		return nil, fmt.Errorf("encoding of %T fact is nondeterministic", fact)
+	}
+
+	new := reflect.New(reflect.TypeOf(fact).Elem()).Interface().(analysis.Fact)
+	if err := gob.NewDecoder(&buf).Decode(new); err != nil {
+		return nil, err
+	}
+	return new, nil
+}
+
+// exportedFrom reports whether obj may be visible to a package that imports pkg.
+// This includes not just the exported members of pkg, but also unexported
+// constants, types, fields, and methods, perhaps belonging to oether packages,
+// that find there way into the API.
+// This is an overapproximation of the more accurate approach used by
+// gc export data, which walks the type graph, but it's much simpler.
+//
+// TODO(adonovan): do more accurate filtering by walking the type graph.
+func exportedFrom(obj types.Object, pkg *types.Package) bool {
+	switch obj := obj.(type) {
+	case *types.Func:
+		return obj.Exported() && obj.Pkg() == pkg ||
+			obj.Type().(*types.Signature).Recv() != nil
+	case *types.Var:
+		return obj.Exported() && obj.Pkg() == pkg ||
+			obj.IsField()
+	case *types.TypeName, *types.Const:
+		return true
+	}
+	return false // Nil, Builtin, Label, or PkgName
+}
+
+// importObjectFact implements Pass.ImportObjectFact.
+// Given a non-nil pointer ptr of type *T, where *T satisfies Fact,
+// importObjectFact copies the fact value to *ptr.
+func (act *action) importObjectFact(obj types.Object, ptr analysis.Fact) bool {
+	if obj == nil {
+		panic("nil object")
+	}
+	key := objectFactKey{obj, factType(ptr)}
+	if v, ok := act.objectFacts[key]; ok {
+		reflect.ValueOf(ptr).Elem().Set(reflect.ValueOf(v).Elem())
+		return true
+	}
+	return false
+}
+
+// exportObjectFact implements Pass.ExportObjectFact.
+func (act *action) exportObjectFact(obj types.Object, fact analysis.Fact) {
+	if act.pass.ExportObjectFact == nil {
+		log.Panicf("%s: Pass.ExportObjectFact(%s, %T) called after Run", act, obj, fact)
+	}
+
+	if obj.Pkg() != act.pkg.Types {
+		log.Panicf("internal error: in analysis %s of package %s: Fact.Set(%s, %T): can't set facts on objects belonging another package",
+			act.a, act.pkg, obj, fact)
+	}
+
+	key := objectFactKey{obj, factType(fact)}
+	act.objectFacts[key] = fact // clobber any existing entry
+	if dbg('f') {
+		objstr := types.ObjectString(obj, (*types.Package).Name)
+		fmt.Fprintf(os.Stderr, "%s: object %s has fact %s\n",
+			act.pkg.Fset.Position(obj.Pos()), objstr, fact)
+	}
+}
+
+// importPackageFact implements Pass.ImportPackageFact.
+// Given a non-nil pointer ptr of type *T, where *T satisfies Fact,
+// fact copies the fact value to *ptr.
+func (act *action) importPackageFact(pkg *types.Package, ptr analysis.Fact) bool {
+	if pkg == nil {
+		panic("nil package")
+	}
+	key := packageFactKey{pkg, factType(ptr)}
+	if v, ok := act.packageFacts[key]; ok {
+		reflect.ValueOf(ptr).Elem().Set(reflect.ValueOf(v).Elem())
+		return true
+	}
+	return false
+}
+
+// exportPackageFact implements Pass.ExportPackageFact.
+func (act *action) exportPackageFact(fact analysis.Fact) {
+	if act.pass.ExportPackageFact == nil {
+		log.Panicf("%s: Pass.ExportPackageFact(%T) called after Run", act, fact)
+	}
+
+	key := packageFactKey{act.pass.Pkg, factType(fact)}
+	act.packageFacts[key] = fact // clobber any existing entry
+	if dbg('f') {
+		fmt.Fprintf(os.Stderr, "%s: package %s has fact %s\n",
+			act.pkg.Fset.Position(act.pass.Files[0].Pos()), act.pass.Pkg.Path(), fact)
+	}
+}
+
+func factType(fact analysis.Fact) reflect.Type {
+	t := reflect.TypeOf(fact)
+	if t.Kind() != reflect.Ptr {
+		log.Fatalf("invalid Fact type: got %T, want pointer", t)
+	}
+	return t
+}
+
+func dbg(b byte) bool { return strings.IndexByte(Debug, b) >= 0 }