// ParseQueryPos parses the source query position pos and returns the
// AST node of the loaded program lprog that it identifies.
// If needExact, it must identify a single AST subtree;
// this is appropriate for queries that allow fairly arbitrary syntax,
// e.g. "describe".
//
func parseQueryPos(lprog *loader.Program, pos string, needExact bool) (*queryPos, error) {
	filename, startOffset, endOffset, err := parsePos(pos)
	if err != nil {
		return nil, err
	}

	// Find the named file among those in the loaded program.
	var file *token.File
	lprog.Fset.Iterate(func(f *token.File) bool {
		if sameFile(filename, f.Name()) {
			file = f
			return false // done
		}
		return true // continue
	})
	if file == nil {
		return nil, fmt.Errorf("file %s not found in loaded program", filename)
	}

	start, end, err := fileOffsetToPos(file, startOffset, endOffset)
	if err != nil {
		return nil, err
	}
	info, path, exact := lprog.PathEnclosingInterval(start, end)
	if path == nil {
		return nil, fmt.Errorf("no syntax here")
	}
	if needExact && !exact {
		return nil, fmt.Errorf("ambiguous selection within %s", astutil.NodeDescription(path[0]))
	}
	return &queryPos{lprog.Fset, start, end, path, exact, info}, nil
}

// describe describes the syntax node denoted by the query position,
// including:
// - its syntactic category
// - the definition of its referent (for identifiers) [now redundant]
// - its type and method set (for an expression or type expression)
//
func describe(o *Oracle, qpos *QueryPos) (queryResult, error) {
	if false { // debugging
		fprintf(os.Stderr, o.fset, qpos.path[0], "you selected: %s %s",
			astutil.NodeDescription(qpos.path[0]), pathToString(qpos.path))
	}

	path, action := findInterestingNode(qpos.info, qpos.path)
	switch action {
	case actionExpr:
		return describeValue(o, qpos, path)

	case actionType:
		return describeType(o, qpos, path)

	case actionPackage:
		return describePackage(o, qpos, path)

	case actionStmt:
		return describeStmt(o, qpos, path)

	case actionUnknown:
		return &describeUnknownResult{path[0]}, nil

	default:
		panic(action) // unreachable
	}
}

func (r *whatResult) display(printf printfFunc) {
	for _, n := range r.path {
		printf(n, "%s", astutil.NodeDescription(n))
	}
	printf(nil, "modes: %s", r.modes)
	printf(nil, "srcdir: %s", r.srcdir)
	printf(nil, "import path: %s", r.importPath)
}

// pointsto runs the pointer analysis on the selected expression,
// and reports its points-to set (for a pointer-like expression)
// or its dynamic types (for an interface, reflect.Value, or
// reflect.Type expression) and their points-to sets.
//
// All printed sets are sorted to ensure determinism.
//
func pointsto(o *Oracle, qpos *QueryPos) (queryResult, error) {
	path, action := findInterestingNode(qpos.info, qpos.path)
	if action != actionExpr {
		return nil, fmt.Errorf("pointer analysis wants an expression; got %s",
			astutil.NodeDescription(qpos.path[0]))
	}

	var expr ast.Expr
	var obj types.Object
	switch n := path[0].(type) {
	case *ast.ValueSpec:
		// ambiguous ValueSpec containing multiple names
		return nil, fmt.Errorf("multiple value specification")
	case *ast.Ident:
		obj = qpos.info.ObjectOf(n)
		expr = n
	case ast.Expr:
		expr = n
	default:
		// TODO(adonovan): is this reachable?
		return nil, fmt.Errorf("unexpected AST for expr: %T", n)
	}

	// Reject non-pointerlike types (includes all constants---except nil).
	// TODO(adonovan): reject nil too.
	typ := qpos.info.TypeOf(expr)
	if !pointer.CanPoint(typ) {
		return nil, fmt.Errorf("pointer analysis wants an expression of reference type; got %s", typ)
	}

	// Determine the ssa.Value for the expression.
	var value ssa.Value
	var isAddr bool
	var err error
	if obj != nil {
		// def/ref of func/var object
		value, isAddr, err = ssaValueForIdent(o.prog, qpos.info, obj, path)
	} else {
		value, isAddr, err = ssaValueForExpr(o.prog, qpos.info, path)
	}
	if err != nil {
		return nil, err // e.g. trivially dead code
	}

	// Run the pointer analysis.
	ptrs, err := runPTA(o, value, isAddr)
	if err != nil {
		return nil, err // e.g. analytically unreachable
	}

	return &pointstoResult{
		qpos: qpos,
		typ:  typ,
		ptrs: ptrs,
	}, nil
}

func (r *whatResult) PrintPlain(printf printfFunc) {
	for _, n := range r.path {
		printf(n, "%s", astutil.NodeDescription(n))
	}
	printf(nil, "modes: %s", r.modes)
	printf(nil, "srcdir: %s", r.srcdir)
	printf(nil, "import path: %s", r.importPath)
	for _, pos := range r.sameids {
		printf(pos, "%s", r.object)
	}
}

// describe describes the syntax node denoted by the query position,
// including:
// - its syntactic category
// - the definition of its referent (for identifiers) [now redundant]
// - its type, fields, and methods (for an expression or type expression)
//
func describe(q *Query) error {
	lconf := loader.Config{Build: q.Build}
	allowErrors(&lconf)

	if _, err := importQueryPackage(q.Pos, &lconf); err != nil {
		return err
	}

	// Load/parse/type-check the program.
	lprog, err := lconf.Load()
	if err != nil {
		return err
	}

	qpos, err := parseQueryPos(lprog, q.Pos, true) // (need exact pos)
	if err != nil {
		return err
	}

	if false { // debugging
		fprintf(os.Stderr, lprog.Fset, qpos.path[0], "you selected: %s %s",
			astutil.NodeDescription(qpos.path[0]), pathToString(qpos.path))
	}

	var qr QueryResult
	path, action := findInterestingNode(qpos.info, qpos.path)
	switch action {
	case actionExpr:
		qr, err = describeValue(qpos, path)

	case actionType:
		qr, err = describeType(qpos, path)

	case actionPackage:
		qr, err = describePackage(qpos, path)

	case actionStmt:
		qr, err = describeStmt(qpos, path)

	case actionUnknown:
		qr = &describeUnknownResult{path[0]}

	default:
		panic(action) // unreachable
	}
	if err != nil {
		return err
	}
	q.Output(lprog.Fset, qr)
	return nil
}

func (r *whatResult) toSerial(res *serial.Result, fset *token.FileSet) {
	var enclosing []serial.SyntaxNode
	for _, n := range r.path {
		enclosing = append(enclosing, serial.SyntaxNode{
			Description: astutil.NodeDescription(n),
			Start:       fset.Position(n.Pos()).Offset,
			End:         fset.Position(n.End()).Offset,
		})
	}
	res.What = &serial.What{
		Modes:      r.modes,
		SrcDir:     r.srcdir,
		ImportPath: r.importPath,
		Enclosing:  enclosing,
	}
}

func describeStmt(o *Oracle, qpos *QueryPos, path []ast.Node) (*describeStmtResult, error) {
	var description string
	switch n := path[0].(type) {
	case *ast.Ident:
		if qpos.info.Defs[n] != nil {
			description = "labelled statement"
		} else {
			description = "reference to labelled statement"
		}

	default:
		// Nothing much to say about statements.
		description = astutil.NodeDescription(n)
	}
	return &describeStmtResult{o.fset, path[0], description}, nil
}

func (r *describeValueResult) PrintPlain(printf printfFunc) {
	var prefix, suffix string
	if r.constVal != nil {
		suffix = fmt.Sprintf(" of value %s", r.constVal)
	}

	// Describe the expression.
	if r.obj != nil {
		switch obj := r.obj.(type) {
		case *types.Func:
			if recv := obj.Type().(*types.Signature).Recv(); recv != nil {
				if _, ok := recv.Type().Underlying().(*types.Interface); ok {
					prefix = "interface method "
				} else {
					prefix = "method "
				}
			}
		case *types.Alias:
			prefix = tokenOf(obj.Orig()) + " "
		}

		if r.obj.Pos() == r.expr.Pos() {
			// defining ident
			printf(r.expr, "definition of %s%s%s", prefix, r.qpos.objectString(r.obj), suffix)
		} else {
			// referring ident
			printf(r.expr, "reference to %s%s%s", prefix, r.qpos.objectString(r.obj), suffix)
			if def := r.obj.Pos(); def != token.NoPos {
				printf(def, "defined here")
			}
		}
	} else {
		desc := astutil.NodeDescription(r.expr)
		if suffix != "" {
			// constant expression
			printf(r.expr, "%s%s", desc, suffix)
		} else {
			// non-constant expression
			printf(r.expr, "%s of type %s", desc, r.qpos.typeString(r.typ))
		}
	}

	printMethods(printf, r.expr, r.methods)
	printFields(printf, r.expr, r.fields)
}

// ParseQueryPos parses the source query position pos and returns the
// AST node of the loaded program lprog that it identifies.
// If needExact, it must identify a single AST subtree;
// this is appropriate for queries that allow fairly arbitrary syntax,
// e.g. "describe".
//
func parseQueryPos(lprog *loader.Program, posFlag string, needExact bool) (*queryPos, error) {
	filename, startOffset, endOffset, err := parsePosFlag(posFlag)
	if err != nil {
		return nil, err
	}
	start, end, err := findQueryPos(lprog.Fset, filename, startOffset, endOffset)
	if err != nil {
		return nil, err
	}
	info, path, exact := lprog.PathEnclosingInterval(start, end)
	if path == nil {
		return nil, fmt.Errorf("no syntax here")
	}
	if needExact && !exact {
		return nil, fmt.Errorf("ambiguous selection within %s", astutil.NodeDescription(path[0]))
	}
	return &queryPos{lprog.Fset, start, end, path, exact, info}, nil
}

func (r *describeValueResult) toSerial(res *serial.Result, fset *token.FileSet) {
	var value, objpos string
	if r.constVal != nil {
		value = r.constVal.String()
	}
	if r.obj != nil {
		objpos = fset.Position(r.obj.Pos()).String()
	}

	res.Describe = &serial.Describe{
		Desc:   astutil.NodeDescription(r.expr),
		Pos:    fset.Position(r.expr.Pos()).String(),
		Detail: "value",
		Value: &serial.DescribeValue{
			Type:   r.qpos.TypeString(r.typ),
			Value:  value,
			ObjPos: objpos,
		},
	}
}

func (r *describeValueResult) JSON(fset *token.FileSet) []byte {
	var value, objpos string
	if r.constVal != nil {
		value = r.constVal.String()
	}
	if r.obj != nil {
		objpos = fset.Position(r.obj.Pos()).String()
	}

	return toJSON(&serial.Describe{
		Desc:   astutil.NodeDescription(r.expr),
		Pos:    fset.Position(r.expr.Pos()).String(),
		Detail: "value",
		Value: &serial.DescribeValue{
			Type:   r.qpos.typeString(r.typ),
			Value:  value,
			ObjPos: objpos,
		},
	})
}

func (r *whatResult) JSON(fset *token.FileSet) []byte {
	var enclosing []serial.SyntaxNode
	for _, n := range r.path {
		enclosing = append(enclosing, serial.SyntaxNode{
			Description: astutil.NodeDescription(n),
			Start:       fset.Position(n.Pos()).Offset,
			End:         fset.Position(n.End()).Offset,
		})
	}

	var sameids []string
	for _, pos := range r.sameids {
		sameids = append(sameids, fset.Position(pos).String())
	}

	return toJSON(&serial.What{
		Modes:      r.modes,
		SrcDir:     r.srcdir,
		ImportPath: r.importPath,
		Enclosing:  enclosing,
		Object:     r.object,
		SameIDs:    sameids,
	})
}

func (r *describeUnknownResult) display(printf printfFunc) {
	// Nothing much to say about misc syntax.
	printf(r.node, "%s", astutil.NodeDescription(r.node))
}

// pointsto runs the pointer analysis on the selected expression,
// and reports its points-to set (for a pointer-like expression)
// or its dynamic types (for an interface, reflect.Value, or
// reflect.Type expression) and their points-to sets.
//
// All printed sets are sorted to ensure determinism.
//
func pointsto(q *Query) error {
	lconf := loader.Config{Build: q.Build}

	if err := setPTAScope(&lconf, q.Scope); err != nil {
		return err
	}

	// Load/parse/type-check the program.
	lprog, err := lconf.Load()
	if err != nil {
		return err
	}
	q.Fset = lprog.Fset

	qpos, err := parseQueryPos(lprog, q.Pos, true) // needs exact pos
	if err != nil {
		return err
	}

	prog := ssautil.CreateProgram(lprog, ssa.GlobalDebug)

	ptaConfig, err := setupPTA(prog, lprog, q.PTALog, q.Reflection)
	if err != nil {
		return err
	}

	path, action := findInterestingNode(qpos.info, qpos.path)
	if action != actionExpr {
		return fmt.Errorf("pointer analysis wants an expression; got %s",
			astutil.NodeDescription(qpos.path[0]))
	}

	var expr ast.Expr
	var obj types.Object
	switch n := path[0].(type) {
	case *ast.ValueSpec:
		// ambiguous ValueSpec containing multiple names
		return fmt.Errorf("multiple value specification")
	case *ast.Ident:
		obj = qpos.info.ObjectOf(n)
		expr = n
	case ast.Expr:
		expr = n
	default:
		// TODO(adonovan): is this reachable?
		return fmt.Errorf("unexpected AST for expr: %T", n)
	}

	// Reject non-pointerlike types (includes all constants---except nil).
	// TODO(adonovan): reject nil too.
	typ := qpos.info.TypeOf(expr)
	if !pointer.CanPoint(typ) {
		return fmt.Errorf("pointer analysis wants an expression of reference type; got %s", typ)
	}

	// Determine the ssa.Value for the expression.
	var value ssa.Value
	var isAddr bool
	if obj != nil {
		// def/ref of func/var object
		value, isAddr, err = ssaValueForIdent(prog, qpos.info, obj, path)
	} else {
		value, isAddr, err = ssaValueForExpr(prog, qpos.info, path)
	}
	if err != nil {
		return err // e.g. trivially dead code
	}

	// Defer SSA construction till after errors are reported.
	prog.Build()

	// Run the pointer analysis.
	ptrs, err := runPTA(ptaConfig, value, isAddr)
	if err != nil {
		return err // e.g. analytically unreachable
	}

	q.result = &pointstoResult{
		qpos: qpos,
		typ:  typ,
		ptrs: ptrs,
	}
	return nil
}

// whicherrs takes an position to an error and tries to find all types, constants
// and global value which a given error can point to and which can be checked from the
// scope where the error lives.
// In short, it returns a list of things that can be checked against in order to handle
// an error properly.
//
// TODO(dmorsing): figure out if fields in errors like *os.PathError.Err
// can be queried recursively somehow.
func whicherrs(q *Query) error {
	lconf := loader.Config{Build: q.Build}

	if err := setPTAScope(&lconf, q.Scope); err != nil {
		return err
	}

	// Load/parse/type-check the program.
	lprog, err := lconf.Load()
	if err != nil {
		return err
	}
	q.Fset = lprog.Fset

	qpos, err := parseQueryPos(lprog, q.Pos, true) // needs exact pos
	if err != nil {
		return err
	}

	prog := ssautil.CreateProgram(lprog, ssa.GlobalDebug)

	ptaConfig, err := setupPTA(prog, lprog, q.PTALog, q.Reflection)
	if err != nil {
		return err
	}

	path, action := findInterestingNode(qpos.info, qpos.path)
	if action != actionExpr {
		return fmt.Errorf("whicherrs wants an expression; got %s",
			astutil.NodeDescription(qpos.path[0]))
	}
	var expr ast.Expr
	var obj types.Object
	switch n := path[0].(type) {
	case *ast.ValueSpec:
		// ambiguous ValueSpec containing multiple names
		return fmt.Errorf("multiple value specification")
	case *ast.Ident:
		obj = qpos.info.ObjectOf(n)
		expr = n
	case ast.Expr:
		expr = n
	default:
		return fmt.Errorf("unexpected AST for expr: %T", n)
	}

	typ := qpos.info.TypeOf(expr)
	if !types.Identical(typ, builtinErrorType) {
		return fmt.Errorf("selection is not an expression of type 'error'")
	}
	// Determine the ssa.Value for the expression.
	var value ssa.Value
	if obj != nil {
		// def/ref of func/var object
		value, _, err = ssaValueForIdent(prog, qpos.info, obj, path)
	} else {
		value, _, err = ssaValueForExpr(prog, qpos.info, path)
	}
	if err != nil {
		return err // e.g. trivially dead code
	}

	// Defer SSA construction till after errors are reported.
	prog.Build()

	globals := findVisibleErrs(prog, qpos)
	constants := findVisibleConsts(prog, qpos)

	res := &whicherrsResult{
		qpos:   qpos,
		errpos: expr.Pos(),
	}

	// TODO(adonovan): the following code is heavily duplicated
	// w.r.t.  "pointsto".  Refactor?

	// Find the instruction which initialized the
	// global error. If more than one instruction has stored to the global
	// remove the global from the set of values that we want to query.
	allFuncs := ssautil.AllFunctions(prog)
	for fn := range allFuncs {
		for _, b := range fn.Blocks {
			for _, instr := range b.Instrs {
				store, ok := instr.(*ssa.Store)
				if !ok {
					continue
				}
				gval, ok := store.Addr.(*ssa.Global)
				if !ok {
					continue
				}
				gbl, ok := globals[gval]
//.........这里部分代码省略.........