Custom resource definition

Co-authored-by: Mathieu Lonjaret <mathieu.lonjaret@gmail.com>

vendor/golang.org/x/tools/go/packages/packages.go

@@ -0,0 +1,956 @@
+// 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 packages
+
+// See doc.go for package documentation and implementation notes.
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/scanner"
+	"go/token"
+	"go/types"
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+
+	"golang.org/x/tools/go/gcexportdata"
+)
+
+// A LoadMode specifies the amount of detail to return when loading.
+// Higher-numbered modes cause Load to return more information,
+// but may be slower. Load may return more information than requested.
+type LoadMode int
+
+const (
+	// LoadFiles finds the packages and computes their source file lists.
+	// Package fields: ID, Name, Errors, GoFiles, and OtherFiles.
+	LoadFiles LoadMode = iota
+
+	// LoadImports adds import information for each package
+	// and its dependencies.
+	// Package fields added: Imports.
+	LoadImports
+
+	// LoadTypes adds type information for package-level
+	// declarations in the packages matching the patterns.
+	// Package fields added: Types, Fset, and IllTyped.
+	// This mode uses type information provided by the build system when
+	// possible, and may fill in the ExportFile field.
+	LoadTypes
+
+	// LoadSyntax adds typed syntax trees for the packages matching the patterns.
+	// Package fields added: Syntax, and TypesInfo, for direct pattern matches only.
+	LoadSyntax
+
+	// LoadAllSyntax adds typed syntax trees for the packages matching the patterns
+	// and all dependencies.
+	// Package fields added: Types, Fset, IllTyped, Syntax, and TypesInfo,
+	// for all packages in the import graph.
+	LoadAllSyntax
+)
+
+// A Config specifies details about how packages should be loaded.
+// The zero value is a valid configuration.
+// Calls to Load do not modify this struct.
+type Config struct {
+	// Mode controls the level of information returned for each package.
+	Mode LoadMode
+
+	// Context specifies the context for the load operation.
+	// If the context is cancelled, the loader may stop early
+	// and return an ErrCancelled error.
+	// If Context is nil, the load cannot be cancelled.
+	Context context.Context
+
+	// Dir is the directory in which to run the build system's query tool
+	// that provides information about the packages.
+	// If Dir is empty, the tool is run in the current directory.
+	Dir string
+
+	// Env is the environment to use when invoking the build system's query tool.
+	// If Env is nil, the current environment is used.
+	// As in os/exec's Cmd, only the last value in the slice for
+	// each environment key is used. To specify the setting of only
+	// a few variables, append to the current environment, as in:
+	//
+	//	opt.Env = append(os.Environ(), "GOOS=plan9", "GOARCH=386")
+	//
+	Env []string
+
+	// BuildFlags is a list of command-line flags to be passed through to
+	// the build system's query tool.
+	BuildFlags []string
+
+	// Fset provides source position information for syntax trees and types.
+	// If Fset is nil, the loader will create a new FileSet.
+	Fset *token.FileSet
+
+	// ParseFile is called to read and parse each file
+	// when preparing a package's type-checked syntax tree.
+	// It must be safe to call ParseFile simultaneously from multiple goroutines.
+	// If ParseFile is nil, the loader will uses parser.ParseFile.
+	//
+	// ParseFile should parse the source from src and use filename only for
+	// recording position information.
+	//
+	// An application may supply a custom implementation of ParseFile
+	// to change the effective file contents or the behavior of the parser,
+	// or to modify the syntax tree. For example, selectively eliminating
+	// unwanted function bodies can significantly accelerate type checking.
+	ParseFile func(fset *token.FileSet, filename string, src []byte) (*ast.File, error)
+
+	// If Tests is set, the loader includes not just the packages
+	// matching a particular pattern but also any related test packages,
+	// including test-only variants of the package and the test executable.
+	//
+	// For example, when using the go command, loading "fmt" with Tests=true
+	// returns four packages, with IDs "fmt" (the standard package),
+	// "fmt [fmt.test]" (the package as compiled for the test),
+	// "fmt_test" (the test functions from source files in package fmt_test),
+	// and "fmt.test" (the test binary).
+	//
+	// In build systems with explicit names for tests,
+	// setting Tests may have no effect.
+	Tests bool
+
+	// Overlay provides a mapping of absolute file paths to file contents.
+	// If the file  with the given path already exists, the parser will use the
+	// alternative file contents provided by the map.
+	//
+	// Overlays provide incomplete support for when a given file doesn't
+	// already exist on disk. See the package doc above for more details.
+	Overlay map[string][]byte
+}
+
+// driver is the type for functions that query the build system for the
+// packages named by the patterns.
+type driver func(cfg *Config, patterns ...string) (*driverResponse, error)
+
+// driverResponse contains the results for a driver query.
+type driverResponse struct {
+	// Sizes, if not nil, is the types.Sizes to use when type checking.
+	Sizes *types.StdSizes
+
+	// Roots is the set of package IDs that make up the root packages.
+	// We have to encode this separately because when we encode a single package
+	// we cannot know if it is one of the roots as that requires knowledge of the
+	// graph it is part of.
+	Roots []string `json:",omitempty"`
+
+	// Packages is the full set of packages in the graph.
+	// The packages are not connected into a graph.
+	// The Imports if populated will be stubs that only have their ID set.
+	// Imports will be connected and then type and syntax information added in a
+	// later pass (see refine).
+	Packages []*Package
+}
+
+// Load loads and returns the Go packages named by the given patterns.
+//
+// Config specifies loading options;
+// nil behaves the same as an empty Config.
+//
+// Load returns an error if any of the patterns was invalid
+// as defined by the underlying build system.
+// It may return an empty list of packages without an error,
+// for instance for an empty expansion of a valid wildcard.
+// Errors associated with a particular package are recorded in the
+// corresponding Package's Errors list, and do not cause Load to
+// return an error. Clients may need to handle such errors before
+// proceeding with further analysis. The PrintErrors function is
+// provided for convenient display of all errors.
+func Load(cfg *Config, patterns ...string) ([]*Package, error) {
+	l := newLoader(cfg)
+	response, err := defaultDriver(&l.Config, patterns...)
+	if err != nil {
+		return nil, err
+	}
+	l.sizes = response.Sizes
+	return l.refine(response.Roots, response.Packages...)
+}
+
+// defaultDriver is a driver that looks for an external driver binary, and if
+// it does not find it falls back to the built in go list driver.
+func defaultDriver(cfg *Config, patterns ...string) (*driverResponse, error) {
+	driver := findExternalDriver(cfg)
+	if driver == nil {
+		driver = goListDriver
+	}
+	return driver(cfg, patterns...)
+}
+
+// A Package describes a loaded Go package.
+type Package struct {
+	// ID is a unique identifier for a package,
+	// in a syntax provided by the underlying build system.
+	//
+	// Because the syntax varies based on the build system,
+	// clients should treat IDs as opaque and not attempt to
+	// interpret them.
+	ID string
+
+	// Name is the package name as it appears in the package source code.
+	Name string
+
+	// PkgPath is the package path as used by the go/types package.
+	PkgPath string
+
+	// Errors contains any errors encountered querying the metadata
+	// of the package, or while parsing or type-checking its files.
+	Errors []Error
+
+	// GoFiles lists the absolute file paths of the package's Go source files.
+	GoFiles []string
+
+	// CompiledGoFiles lists the absolute file paths of the package's source
+	// files that were presented to the compiler.
+	// This may differ from GoFiles if files are processed before compilation.
+	CompiledGoFiles []string
+
+	// OtherFiles lists the absolute file paths of the package's non-Go source files,
+	// including assembly, C, C++, Fortran, Objective-C, SWIG, and so on.
+	OtherFiles []string
+
+	// ExportFile is the absolute path to a file containing type
+	// information for the package as provided by the build system.
+	ExportFile string
+
+	// Imports maps import paths appearing in the package's Go source files
+	// to corresponding loaded Packages.
+	Imports map[string]*Package
+
+	// Types provides type information for the package.
+	// Modes LoadTypes and above set this field for packages matching the
+	// patterns; type information for dependencies may be missing or incomplete.
+	// Mode LoadAllSyntax sets this field for all packages, including dependencies.
+	Types *types.Package
+
+	// Fset provides position information for Types, TypesInfo, and Syntax.
+	// It is set only when Types is set.
+	Fset *token.FileSet
+
+	// IllTyped indicates whether the package or any dependency contains errors.
+	// It is set only when Types is set.
+	IllTyped bool
+
+	// Syntax is the package's syntax trees, for the files listed in CompiledGoFiles.
+	//
+	// Mode LoadSyntax sets this field for packages matching the patterns.
+	// Mode LoadAllSyntax sets this field for all packages, including dependencies.
+	Syntax []*ast.File
+
+	// TypesInfo provides type information about the package's syntax trees.
+	// It is set only when Syntax is set.
+	TypesInfo *types.Info
+
+	// TypesSizes provides the effective size function for types in TypesInfo.
+	TypesSizes types.Sizes
+}
+
+// An Error describes a problem with a package's metadata, syntax, or types.
+type Error struct {
+	Pos  string // "file:line:col" or "file:line" or "" or "-"
+	Msg  string
+	Kind ErrorKind
+}
+
+// ErrorKind describes the source of the error, allowing the user to
+// differentiate between errors generated by the driver, the parser, or the
+// type-checker.
+type ErrorKind int
+
+const (
+	UnknownError ErrorKind = iota
+	ListError
+	ParseError
+	TypeError
+)
+
+func (err Error) Error() string {
+	pos := err.Pos
+	if pos == "" {
+		pos = "-" // like token.Position{}.String()
+	}
+	return pos + ": " + err.Msg
+}
+
+// flatPackage is the JSON form of Package
+// It drops all the type and syntax fields, and transforms the Imports
+//
+// TODO(adonovan): identify this struct with Package, effectively
+// publishing the JSON protocol.
+type flatPackage struct {
+	ID              string
+	Name            string            `json:",omitempty"`
+	PkgPath         string            `json:",omitempty"`
+	Errors          []Error           `json:",omitempty"`
+	GoFiles         []string          `json:",omitempty"`
+	CompiledGoFiles []string          `json:",omitempty"`
+	OtherFiles      []string          `json:",omitempty"`
+	ExportFile      string            `json:",omitempty"`
+	Imports         map[string]string `json:",omitempty"`
+}
+
+// MarshalJSON returns the Package in its JSON form.
+// For the most part, the structure fields are written out unmodified, and
+// the type and syntax fields are skipped.
+// The imports are written out as just a map of path to package id.
+// The errors are written using a custom type that tries to preserve the
+// structure of error types we know about.
+//
+// This method exists to enable support for additional build systems.  It is
+// not intended for use by clients of the API and we may change the format.
+func (p *Package) MarshalJSON() ([]byte, error) {
+	flat := &flatPackage{
+		ID:              p.ID,
+		Name:            p.Name,
+		PkgPath:         p.PkgPath,
+		Errors:          p.Errors,
+		GoFiles:         p.GoFiles,
+		CompiledGoFiles: p.CompiledGoFiles,
+		OtherFiles:      p.OtherFiles,
+		ExportFile:      p.ExportFile,
+	}
+	if len(p.Imports) > 0 {
+		flat.Imports = make(map[string]string, len(p.Imports))
+		for path, ipkg := range p.Imports {
+			flat.Imports[path] = ipkg.ID
+		}
+	}
+	return json.Marshal(flat)
+}
+
+// UnmarshalJSON reads in a Package from its JSON format.
+// See MarshalJSON for details about the format accepted.
+func (p *Package) UnmarshalJSON(b []byte) error {
+	flat := &flatPackage{}
+	if err := json.Unmarshal(b, &flat); err != nil {
+		return err
+	}
+	*p = Package{
+		ID:              flat.ID,
+		Name:            flat.Name,
+		PkgPath:         flat.PkgPath,
+		Errors:          flat.Errors,
+		GoFiles:         flat.GoFiles,
+		CompiledGoFiles: flat.CompiledGoFiles,
+		OtherFiles:      flat.OtherFiles,
+		ExportFile:      flat.ExportFile,
+	}
+	if len(flat.Imports) > 0 {
+		p.Imports = make(map[string]*Package, len(flat.Imports))
+		for path, id := range flat.Imports {
+			p.Imports[path] = &Package{ID: id}
+		}
+	}
+	return nil
+}
+
+func (p *Package) String() string { return p.ID }
+
+// loaderPackage augments Package with state used during the loading phase
+type loaderPackage struct {
+	*Package
+	importErrors map[string]error // maps each bad import to its error
+	loadOnce     sync.Once
+	color        uint8 // for cycle detection
+	needsrc      bool  // load from source (Mode >= LoadTypes)
+	needtypes    bool  // type information is either requested or depended on
+	initial      bool  // package was matched by a pattern
+}
+
+// loader holds the working state of a single call to load.
+type loader struct {
+	pkgs map[string]*loaderPackage
+	Config
+	sizes    types.Sizes
+	exportMu sync.Mutex // enforces mutual exclusion of exportdata operations
+}
+
+func newLoader(cfg *Config) *loader {
+	ld := &loader{}
+	if cfg != nil {
+		ld.Config = *cfg
+	}
+	if ld.Config.Env == nil {
+		ld.Config.Env = os.Environ()
+	}
+	if ld.Context == nil {
+		ld.Context = context.Background()
+	}
+	if ld.Dir == "" {
+		if dir, err := os.Getwd(); err == nil {
+			ld.Dir = dir
+		}
+	}
+
+	if ld.Mode >= LoadTypes {
+		if ld.Fset == nil {
+			ld.Fset = token.NewFileSet()
+		}
+
+		// ParseFile is required even in LoadTypes mode
+		// because we load source if export data is missing.
+		if ld.ParseFile == nil {
+			ld.ParseFile = func(fset *token.FileSet, filename string, src []byte) (*ast.File, error) {
+				var isrc interface{}
+				if src != nil {
+					isrc = src
+				}
+				const mode = parser.AllErrors | parser.ParseComments
+				return parser.ParseFile(fset, filename, isrc, mode)
+			}
+		}
+	}
+	return ld
+}
+
+// refine connects the supplied packages into a graph and then adds type and
+// and syntax information as requested by the LoadMode.
+func (ld *loader) refine(roots []string, list ...*Package) ([]*Package, error) {
+	rootMap := make(map[string]int, len(roots))
+	for i, root := range roots {
+		rootMap[root] = i
+	}
+	ld.pkgs = make(map[string]*loaderPackage)
+	// first pass, fixup and build the map and roots
+	var initial = make([]*loaderPackage, len(roots))
+	for _, pkg := range list {
+		rootIndex := -1
+		if i, found := rootMap[pkg.ID]; found {
+			rootIndex = i
+		}
+		lpkg := &loaderPackage{
+			Package: pkg,
+			needtypes: ld.Mode >= LoadAllSyntax ||
+				ld.Mode >= LoadTypes && rootIndex >= 0,
+			needsrc: ld.Mode >= LoadAllSyntax ||
+				ld.Mode >= LoadSyntax && rootIndex >= 0 ||
+				len(ld.Overlay) > 0 || // Overlays can invalidate export data. TODO(matloob): make this check fine-grained based on dependencies on overlaid files
+				pkg.ExportFile == "" && pkg.PkgPath != "unsafe",
+		}
+		ld.pkgs[lpkg.ID] = lpkg
+		if rootIndex >= 0 {
+			initial[rootIndex] = lpkg
+			lpkg.initial = true
+		}
+	}
+	for i, root := range roots {
+		if initial[i] == nil {
+			return nil, fmt.Errorf("root package %v is missing", root)
+		}
+	}
+
+	// Materialize the import graph.
+
+	const (
+		white = 0 // new
+		grey  = 1 // in progress
+		black = 2 // complete
+	)
+
+	// visit traverses the import graph, depth-first,
+	// and materializes the graph as Packages.Imports.
+	//
+	// Valid imports are saved in the Packages.Import map.
+	// Invalid imports (cycles and missing nodes) are saved in the importErrors map.
+	// Thus, even in the presence of both kinds of errors, the Import graph remains a DAG.
+	//
+	// visit returns whether the package needs src or has a transitive
+	// dependency on a package that does. These are the only packages
+	// for which we load source code.
+	var stack []*loaderPackage
+	var visit func(lpkg *loaderPackage) bool
+	var srcPkgs []*loaderPackage
+	visit = func(lpkg *loaderPackage) bool {
+		switch lpkg.color {
+		case black:
+			return lpkg.needsrc
+		case grey:
+			panic("internal error: grey node")
+		}
+		lpkg.color = grey
+		stack = append(stack, lpkg) // push
+		stubs := lpkg.Imports       // the structure form has only stubs with the ID in the Imports
+		lpkg.Imports = make(map[string]*Package, len(stubs))
+		for importPath, ipkg := range stubs {
+			var importErr error
+			imp := ld.pkgs[ipkg.ID]
+			if imp == nil {
+				// (includes package "C" when DisableCgo)
+				importErr = fmt.Errorf("missing package: %q", ipkg.ID)
+			} else if imp.color == grey {
+				importErr = fmt.Errorf("import cycle: %s", stack)
+			}
+			if importErr != nil {
+				if lpkg.importErrors == nil {
+					lpkg.importErrors = make(map[string]error)
+				}
+				lpkg.importErrors[importPath] = importErr
+				continue
+			}
+
+			if visit(imp) {
+				lpkg.needsrc = true
+			}
+			lpkg.Imports[importPath] = imp.Package
+		}
+		if lpkg.needsrc {
+			srcPkgs = append(srcPkgs, lpkg)
+		}
+		stack = stack[:len(stack)-1] // pop
+		lpkg.color = black
+
+		return lpkg.needsrc
+	}
+
+	if ld.Mode < LoadImports {
+		//we do this to drop the stub import packages that we are not even going to try to resolve
+		for _, lpkg := range initial {
+			lpkg.Imports = nil
+		}
+	} else {
+		// For each initial package, create its import DAG.
+		for _, lpkg := range initial {
+			visit(lpkg)
+		}
+	}
+	for _, lpkg := range srcPkgs {
+		// Complete type information is required for the
+		// immediate dependencies of each source package.
+		for _, ipkg := range lpkg.Imports {
+			imp := ld.pkgs[ipkg.ID]
+			imp.needtypes = true
+		}
+	}
+	// Load type data if needed, starting at
+	// the initial packages (roots of the import DAG).
+	if ld.Mode >= LoadTypes {
+		var wg sync.WaitGroup
+		for _, lpkg := range initial {
+			wg.Add(1)
+			go func(lpkg *loaderPackage) {
+				ld.loadRecursive(lpkg)
+				wg.Done()
+			}(lpkg)
+		}
+		wg.Wait()
+	}
+
+	result := make([]*Package, len(initial))
+	for i, lpkg := range initial {
+		result[i] = lpkg.Package
+	}
+	return result, nil
+}
+
+// loadRecursive loads the specified package and its dependencies,
+// recursively, in parallel, in topological order.
+// It is atomic and idempotent.
+// Precondition: ld.Mode >= LoadTypes.
+func (ld *loader) loadRecursive(lpkg *loaderPackage) {
+	lpkg.loadOnce.Do(func() {
+		// Load the direct dependencies, in parallel.
+		var wg sync.WaitGroup
+		for _, ipkg := range lpkg.Imports {
+			imp := ld.pkgs[ipkg.ID]
+			wg.Add(1)
+			go func(imp *loaderPackage) {
+				ld.loadRecursive(imp)
+				wg.Done()
+			}(imp)
+		}
+		wg.Wait()
+
+		ld.loadPackage(lpkg)
+	})
+}
+
+// loadPackage loads the specified package.
+// It must be called only once per Package,
+// after immediate dependencies are loaded.
+// Precondition: ld.Mode >= LoadTypes.
+func (ld *loader) loadPackage(lpkg *loaderPackage) {
+	if lpkg.PkgPath == "unsafe" {
+		// Fill in the blanks to avoid surprises.
+		lpkg.Types = types.Unsafe
+		lpkg.Fset = ld.Fset
+		lpkg.Syntax = []*ast.File{}
+		lpkg.TypesInfo = new(types.Info)
+		lpkg.TypesSizes = ld.sizes
+		return
+	}
+
+	// Call NewPackage directly with explicit name.
+	// This avoids skew between golist and go/types when the files'
+	// package declarations are inconsistent.
+	lpkg.Types = types.NewPackage(lpkg.PkgPath, lpkg.Name)
+	lpkg.Fset = ld.Fset
+
+	// Subtle: we populate all Types fields with an empty Package
+	// before loading export data so that export data processing
+	// never has to create a types.Package for an indirect dependency,
+	// which would then require that such created packages be explicitly
+	// inserted back into the Import graph as a final step after export data loading.
+	// The Diamond test exercises this case.
+	if !lpkg.needtypes {
+		return
+	}
+	if !lpkg.needsrc {
+		ld.loadFromExportData(lpkg)
+		return // not a source package, don't get syntax trees
+	}
+
+	appendError := func(err error) {
+		// Convert various error types into the one true Error.
+		var errs []Error
+		switch err := err.(type) {
+		case Error:
+			// from driver
+			errs = append(errs, err)
+
+		case *os.PathError:
+			// from parser
+			errs = append(errs, Error{
+				Pos:  err.Path + ":1",
+				Msg:  err.Err.Error(),
+				Kind: ParseError,
+			})
+
+		case scanner.ErrorList:
+			// from parser
+			for _, err := range err {
+				errs = append(errs, Error{
+					Pos:  err.Pos.String(),
+					Msg:  err.Msg,
+					Kind: ParseError,
+				})
+			}
+
+		case types.Error:
+			// from type checker
+			errs = append(errs, Error{
+				Pos:  err.Fset.Position(err.Pos).String(),
+				Msg:  err.Msg,
+				Kind: TypeError,
+			})
+
+		default:
+			// unexpected impoverished error from parser?
+			errs = append(errs, Error{
+				Pos:  "-",
+				Msg:  err.Error(),
+				Kind: UnknownError,
+			})
+
+			// If you see this error message, please file a bug.
+			log.Printf("internal error: error %q (%T) without position", err, err)
+		}
+
+		lpkg.Errors = append(lpkg.Errors, errs...)
+	}
+
+	files, errs := ld.parseFiles(lpkg.CompiledGoFiles)
+	for _, err := range errs {
+		appendError(err)
+	}
+
+	lpkg.Syntax = files
+
+	lpkg.TypesInfo = &types.Info{
+		Types:      make(map[ast.Expr]types.TypeAndValue),
+		Defs:       make(map[*ast.Ident]types.Object),
+		Uses:       make(map[*ast.Ident]types.Object),
+		Implicits:  make(map[ast.Node]types.Object),
+		Scopes:     make(map[ast.Node]*types.Scope),
+		Selections: make(map[*ast.SelectorExpr]*types.Selection),
+	}
+	lpkg.TypesSizes = ld.sizes
+
+	importer := importerFunc(func(path string) (*types.Package, error) {
+		if path == "unsafe" {
+			return types.Unsafe, nil
+		}
+
+		// The imports map is keyed by import path.
+		ipkg := lpkg.Imports[path]
+		if ipkg == nil {
+			if err := lpkg.importErrors[path]; err != nil {
+				return nil, err
+			}
+			// There was skew between the metadata and the
+			// import declarations, likely due to an edit
+			// race, or because the ParseFile feature was
+			// used to supply alternative file contents.
+			return nil, fmt.Errorf("no metadata for %s", path)
+		}
+
+		if ipkg.Types != nil && ipkg.Types.Complete() {
+			return ipkg.Types, nil
+		}
+		log.Fatalf("internal error: nil Pkg importing %q from %q", path, lpkg)
+		panic("unreachable")
+	})
+
+	// type-check
+	tc := &types.Config{
+		Importer: importer,
+
+		// Type-check bodies of functions only in non-initial packages.
+		// Example: for import graph A->B->C and initial packages {A,C},
+		// we can ignore function bodies in B.
+		IgnoreFuncBodies: ld.Mode < LoadAllSyntax && !lpkg.initial,
+
+		Error: appendError,
+		Sizes: ld.sizes,
+	}
+	types.NewChecker(tc, ld.Fset, lpkg.Types, lpkg.TypesInfo).Files(lpkg.Syntax)
+
+	lpkg.importErrors = nil // no longer needed
+
+	// If !Cgo, the type-checker uses FakeImportC mode, so
+	// it doesn't invoke the importer for import "C",
+	// nor report an error for the import,
+	// or for any undefined C.f reference.
+	// We must detect this explicitly and correctly
+	// mark the package as IllTyped (by reporting an error).
+	// TODO(adonovan): if these errors are annoying,
+	// we could just set IllTyped quietly.
+	if tc.FakeImportC {
+	outer:
+		for _, f := range lpkg.Syntax {
+			for _, imp := range f.Imports {
+				if imp.Path.Value == `"C"` {
+					err := types.Error{Fset: ld.Fset, Pos: imp.Pos(), Msg: `import "C" ignored`}
+					appendError(err)
+					break outer
+				}
+			}
+		}
+	}
+
+	// Record accumulated errors.
+	illTyped := len(lpkg.Errors) > 0
+	if !illTyped {
+		for _, imp := range lpkg.Imports {
+			if imp.IllTyped {
+				illTyped = true
+				break
+			}
+		}
+	}
+	lpkg.IllTyped = illTyped
+}
+
+// An importFunc is an implementation of the single-method
+// types.Importer interface based on a function value.
+type importerFunc func(path string) (*types.Package, error)
+
+func (f importerFunc) Import(path string) (*types.Package, error) { return f(path) }
+
+// We use a counting semaphore to limit
+// the number of parallel I/O calls per process.
+var ioLimit = make(chan bool, 20)
+
+// parseFiles reads and parses the Go source files and returns the ASTs
+// of the ones that could be at least partially parsed, along with a
+// list of I/O and parse errors encountered.
+//
+// Because files are scanned in parallel, the token.Pos
+// positions of the resulting ast.Files are not ordered.
+//
+func (ld *loader) parseFiles(filenames []string) ([]*ast.File, []error) {
+	var wg sync.WaitGroup
+	n := len(filenames)
+	parsed := make([]*ast.File, n)
+	errors := make([]error, n)
+	for i, file := range filenames {
+		if ld.Config.Context.Err() != nil {
+			parsed[i] = nil
+			errors[i] = ld.Config.Context.Err()
+			continue
+		}
+		wg.Add(1)
+		go func(i int, filename string) {
+			ioLimit <- true // wait
+			// ParseFile may return both an AST and an error.
+			var src []byte
+			for f, contents := range ld.Config.Overlay {
+				if sameFile(f, filename) {
+					src = contents
+				}
+			}
+			var err error
+			if src == nil {
+				src, err = ioutil.ReadFile(filename)
+			}
+			if err != nil {
+				parsed[i], errors[i] = nil, err
+			} else {
+				parsed[i], errors[i] = ld.ParseFile(ld.Fset, filename, src)
+			}
+			<-ioLimit // signal
+			wg.Done()
+		}(i, file)
+	}
+	wg.Wait()
+
+	// Eliminate nils, preserving order.
+	var o int
+	for _, f := range parsed {
+		if f != nil {
+			parsed[o] = f
+			o++
+		}
+	}
+	parsed = parsed[:o]
+
+	o = 0
+	for _, err := range errors {
+		if err != nil {
+			errors[o] = err
+			o++
+		}
+	}
+	errors = errors[:o]
+
+	return parsed, errors
+}
+
+// sameFile returns true if x and y have the same basename and denote
+// the same file.
+//
+func sameFile(x, y string) bool {
+	if x == y {
+		// It could be the case that y doesn't exist.
+		// For instance, it may be an overlay file that
+		// hasn't been written to disk. To handle that case
+		// let x == y through. (We added the exact absolute path
+		// string to the CompiledGoFiles list, so the unwritten
+		// overlay case implies x==y.)
+		return true
+	}
+	if strings.EqualFold(filepath.Base(x), filepath.Base(y)) { // (optimisation)
+		if xi, err := os.Stat(x); err == nil {
+			if yi, err := os.Stat(y); err == nil {
+				return os.SameFile(xi, yi)
+			}
+		}
+	}
+	return false
+}
+
+// loadFromExportData returns type information for the specified
+// package, loading it from an export data file on the first request.
+func (ld *loader) loadFromExportData(lpkg *loaderPackage) (*types.Package, error) {
+	if lpkg.PkgPath == "" {
+		log.Fatalf("internal error: Package %s has no PkgPath", lpkg)
+	}
+
+	// Because gcexportdata.Read has the potential to create or
+	// modify the types.Package for each node in the transitive
+	// closure of dependencies of lpkg, all exportdata operations
+	// must be sequential. (Finer-grained locking would require
+	// changes to the gcexportdata API.)
+	//
+	// The exportMu lock guards the Package.Pkg field and the
+	// types.Package it points to, for each Package in the graph.
+	//
+	// Not all accesses to Package.Pkg need to be protected by exportMu:
+	// graph ordering ensures that direct dependencies of source
+	// packages are fully loaded before the importer reads their Pkg field.
+	ld.exportMu.Lock()
+	defer ld.exportMu.Unlock()
+
+	if tpkg := lpkg.Types; tpkg != nil && tpkg.Complete() {
+		return tpkg, nil // cache hit
+	}
+
+	lpkg.IllTyped = true // fail safe
+
+	if lpkg.ExportFile == "" {
+		// Errors while building export data will have been printed to stderr.
+		return nil, fmt.Errorf("no export data file")
+	}
+	f, err := os.Open(lpkg.ExportFile)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	// Read gc export data.
+	//
+	// We don't currently support gccgo export data because all
+	// underlying workspaces use the gc toolchain. (Even build
+	// systems that support gccgo don't use it for workspace
+	// queries.)
+	r, err := gcexportdata.NewReader(f)
+	if err != nil {
+		return nil, fmt.Errorf("reading %s: %v", lpkg.ExportFile, err)
+	}
+
+	// Build the view.
+	//
+	// The gcexportdata machinery has no concept of package ID.
+	// It identifies packages by their PkgPath, which although not
+	// globally unique is unique within the scope of one invocation
+	// of the linker, type-checker, or gcexportdata.
+	//
+	// So, we must build a PkgPath-keyed view of the global
+	// (conceptually ID-keyed) cache of packages and pass it to
+	// gcexportdata. The view must contain every existing
+	// package that might possibly be mentioned by the
+	// current package---its transitive closure.
+	//
+	// In loadPackage, we unconditionally create a types.Package for
+	// each dependency so that export data loading does not
+	// create new ones.
+	//
+	// TODO(adonovan): it would be simpler and more efficient
+	// if the export data machinery invoked a callback to
+	// get-or-create a package instead of a map.
+	//
+	view := make(map[string]*types.Package) // view seen by gcexportdata
+	seen := make(map[*loaderPackage]bool)   // all visited packages
+	var visit func(pkgs map[string]*Package)
+	visit = func(pkgs map[string]*Package) {
+		for _, p := range pkgs {
+			lpkg := ld.pkgs[p.ID]
+			if !seen[lpkg] {
+				seen[lpkg] = true
+				view[lpkg.PkgPath] = lpkg.Types
+				visit(lpkg.Imports)
+			}
+		}
+	}
+	visit(lpkg.Imports)
+
+	viewLen := len(view) + 1 // adding the self package
+	// Parse the export data.
+	// (May modify incomplete packages in view but not create new ones.)
+	tpkg, err := gcexportdata.Read(r, ld.Fset, view, lpkg.PkgPath)
+	if err != nil {
+		return nil, fmt.Errorf("reading %s: %v", lpkg.ExportFile, err)
+	}
+	if viewLen != len(view) {
+		log.Fatalf("Unexpected package creation during export data loading")
+	}
+
+	lpkg.Types = tpkg
+	lpkg.IllTyped = false
+
+	return tpkg, nil
+}
+
+func usesExportData(cfg *Config) bool {
+	return LoadTypes <= cfg.Mode && cfg.Mode < LoadAllSyntax
+}