go/analysis/passes/printf/types.go - tools - Git at Google

 // 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 printf

 import (
 	"fmt"
 	"go/ast"
 	"go/types"

 	"golang.org/x/tools/go/analysis"
 	"golang.org/x/tools/internal/typeparams"
 )

 var errorType = types.Universe.Lookup("error").Type().Underlying().(*types.Interface)

 // matchArgType reports an error if printf verb t is not appropriate for
 // operand arg.
 //
 // If arg is a type parameter, the verb t must be appropriate for every type in
 // the type parameter type set.
 func matchArgType(pass *analysis.Pass, t printfArgType, arg ast.Expr) (reason string, ok bool) {
 	// %v, %T accept any argument type.
 	if t == anyType {
 		return "", true
 	}

 	typ := pass.TypesInfo.Types[arg].Type
 	if typ == nil {
 		return "", true // probably a type check problem
 	}

 	m := &argMatcher{t: t, seen: make(map[types.Type]bool)}
 	ok = m.match(typ, true)
 	return m.reason, ok
 }

 // argMatcher recursively matches types against the printfArgType t.
 //
 // To short-circuit recursion, it keeps track of types that have already been
 // matched (or are in the process of being matched) via the seen map. Recursion
 // arises from the compound types {map,chan,slice} which may be printed with %d
 // etc. if that is appropriate for their element types, as well as from type
 // parameters, which are expanded to the constituents of their type set.
 //
 // The reason field may be set to report the cause of the mismatch.
 type argMatcher struct {
 	t      printfArgType
 	seen   map[types.Type]bool
 	reason string
 }

 // match checks if typ matches m's printf arg type. If topLevel is true, typ is
 // the actual type of the printf arg, for which special rules apply. As a
 // special case, top level type parameters pass topLevel=true when checking for
 // matches among the constituents of their type set, as type arguments will
 // replace the type parameter at compile time.
 func (m *argMatcher) match(typ types.Type, topLevel bool) bool {
 	// %w accepts only errors.
 	if m.t == argError {
 		return types.ConvertibleTo(typ, errorType)
 	}

 	// If the type implements fmt.Formatter, we have nothing to check.
 	if isFormatter(typ) {
 		return true
 	}

 	// If we can use a string, might arg (dynamically) implement the Stringer or Error interface?
 	if m.t&argString != 0 && isConvertibleToString(typ) {
 		return true
 	}

 	if typ, _ := typ.(*typeparams.TypeParam); typ != nil {
 		// Avoid infinite recursion through type parameters.
 		if m.seen[typ] {
 			return true
 		}
 		m.seen[typ] = true
 		terms, err := typeparams.StructuralTerms(typ)
 		if err != nil {
 			return true // invalid type (possibly an empty type set)
 		}

 		if len(terms) == 0 {
 			// No restrictions on the underlying of typ. Type parameters implementing
 			// error, fmt.Formatter, or fmt.Stringer were handled above, and %v and
 			// %T was handled in matchType. We're about to check restrictions the
 			// underlying; if the underlying type is unrestricted there must be an
 			// element of the type set that violates one of the arg type checks
 			// below, so we can safely return false here.

 			if m.t == anyType { // anyType must have already been handled.
 				panic("unexpected printfArgType")
 			}
 			return false
 		}

 		// Only report a reason if typ is the argument type, otherwise it won't
 		// make sense. Note that it is not sufficient to check if topLevel == here,
 		// as type parameters can have a type set consisting of other type
 		// parameters.
 		reportReason := len(m.seen) == 1

 		for _, term := range terms {
 			if !m.match(term.Type(), topLevel) {
 				if reportReason {
 					if term.Tilde() {
 						m.reason = fmt.Sprintf("contains ~%s", term.Type())
 					} else {
 						m.reason = fmt.Sprintf("contains %s", term.Type())
 					}
 				}
 				return false
 			}
 		}
 		return true
 	}

 	typ = typ.Underlying()
 	if m.seen[typ] {
 		// We've already considered typ, or are in the process of considering it.
 		// In case we've already considered typ, it must have been valid (else we
 		// would have stopped matching). In case we're in the process of
 		// considering it, we must avoid infinite recursion.
 		//
 		// There are some pathological cases where returning true here is
 		// incorrect, for example `type R struct { F []R }`, but these are
 		// acceptable false negatives.
 		return true
 	}
 	m.seen[typ] = true

 	switch typ := typ.(type) {
 	case *types.Signature:
 		return m.t == argPointer

 	case *types.Map:
 		if m.t == argPointer {
 			return true
 		}
 		// Recur: map[int]int matches %d.
 		return m.match(typ.Key(), false) && m.match(typ.Elem(), false)

 	case *types.Chan:
 		return m.t&argPointer != 0

 	case *types.Array:
 		// Same as slice.
 		if types.Identical(typ.Elem().Underlying(), types.Typ[types.Byte]) && m.t&argString != 0 {
 			return true // %s matches []byte
 		}
 		// Recur: []int matches %d.
 		return m.match(typ.Elem(), false)

 	case *types.Slice:
 		// Same as array.
 		if types.Identical(typ.Elem().Underlying(), types.Typ[types.Byte]) && m.t&argString != 0 {
 			return true // %s matches []byte
 		}
 		if m.t == argPointer {
 			return true // %p prints a slice's 0th element
 		}
 		// Recur: []int matches %d. But watch out for
 		//	type T []T
 		// If the element is a pointer type (type T[]*T), it's handled fine by the Pointer case below.
 		return m.match(typ.Elem(), false)

 	case *types.Pointer:
 		// Ugly, but dealing with an edge case: a known pointer to an invalid type,
 		// probably something from a failed import.
 		if typ.Elem() == types.Typ[types.Invalid] {
 			return true // special case
 		}
 		// If it's actually a pointer with %p, it prints as one.
 		if m.t == argPointer {
 			return true
 		}

 		if typeparams.IsTypeParam(typ.Elem()) {
 			return true // We don't know whether the logic below applies. Give up.
 		}

 		under := typ.Elem().Underlying()
 		switch under.(type) {
 		case *types.Struct: // see below
 		case *types.Array: // see below
 		case *types.Slice: // see below
 		case *types.Map: // see below
 		default:
 			// Check whether the rest can print pointers.
 			return m.t&argPointer != 0
 		}
 		// If it's a top-level pointer to a struct, array, slice, type param, or
 		// map, that's equivalent in our analysis to whether we can
 		// print the type being pointed to. Pointers in nested levels
 		// are not supported to minimize fmt running into loops.
 		if !topLevel {
 			return false
 		}
 		return m.match(under, false)

 	case *types.Struct:
 		// report whether all the elements of the struct match the expected type. For
 		// instance, with "%d" all the elements must be printable with the "%d" format.
 		for i := 0; i < typ.NumFields(); i++ {
 			typf := typ.Field(i)
 			if !m.match(typf.Type(), false) {
 				return false
 			}
 			if m.t&argString != 0 && !typf.Exported() && isConvertibleToString(typf.Type()) {
 				// Issue #17798: unexported Stringer or error cannot be properly formatted.
 				return false
 			}
 		}
 		return true

 	case *types.Interface:
 		// There's little we can do.
 		// Whether any particular verb is valid depends on the argument.
 		// The user may have reasonable prior knowledge of the contents of the interface.
 		return true

 	case *types.Basic:
 		switch typ.Kind() {
 		case types.UntypedBool,
 			types.Bool:
 			return m.t&argBool != 0

 		case types.UntypedInt,
 			types.Int,
 			types.Int8,
 			types.Int16,
 			types.Int32,
 			types.Int64,
 			types.Uint,
 			types.Uint8,
 			types.Uint16,
 			types.Uint32,
 			types.Uint64,
 			types.Uintptr:
 			return m.t&argInt != 0

 		case types.UntypedFloat,
 			types.Float32,
 			types.Float64:
 			return m.t&argFloat != 0

 		case types.UntypedComplex,
 			types.Complex64,
 			types.Complex128:
 			return m.t&argComplex != 0

 		case types.UntypedString,
 			types.String:
 			return m.t&argString != 0

 		case types.UnsafePointer:
 			return m.t&(argPointer|argInt) != 0

 		case types.UntypedRune:
 			return m.t&(argInt|argRune) != 0

 		case types.UntypedNil:
 			return false

 		case types.Invalid:
 			return true // Probably a type check problem.
 		}
 		panic("unreachable")
 	}

 	return false
 }

 func isConvertibleToString(typ types.Type) bool {
 	if bt, ok := typ.(*types.Basic); ok && bt.Kind() == types.UntypedNil {
 		// We explicitly don't want untyped nil, which is
 		// convertible to both of the interfaces below, as it
 		// would just panic anyway.
 		return false
 	}
 	if types.ConvertibleTo(typ, errorType) {
 		return true // via .Error()
 	}

 	// Does it implement fmt.Stringer?
 	if obj, _, _ := types.LookupFieldOrMethod(typ, false, nil, "String"); obj != nil {
 		if fn, ok := obj.(*types.Func); ok {
 			sig := fn.Type().(*types.Signature)
 			if sig.Params().Len() == 0 &&
 				sig.Results().Len() == 1 &&
 				sig.Results().At(0).Type() == types.Typ[types.String] {
 				return true
 			}
 		}
 	}

 	return false
 }
	// 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 printf

	import (
	"fmt"
	"go/ast"
	"go/types"

	"golang.org/x/tools/go/analysis"
	"golang.org/x/tools/internal/typeparams"
	)

	var errorType = types.Universe.Lookup("error").Type().Underlying().(*types.Interface)

	// matchArgType reports an error if printf verb t is not appropriate for
	// operand arg.
	//
	// If arg is a type parameter, the verb t must be appropriate for every type in
	// the type parameter type set.
	func matchArgType(pass *analysis.Pass, t printfArgType, arg ast.Expr) (reason string, ok bool) {
	// %v, %T accept any argument type.
	if t == anyType {
	return "", true
	}

	typ := pass.TypesInfo.Types[arg].Type
	if typ == nil {
	return "", true // probably a type check problem
	}

	m := &argMatcher{t: t, seen: make(map[types.Type]bool)}
	ok = m.match(typ, true)
	return m.reason, ok
	}

	// argMatcher recursively matches types against the printfArgType t.
	//
	// To short-circuit recursion, it keeps track of types that have already been
	// matched (or are in the process of being matched) via the seen map. Recursion
	// arises from the compound types {map,chan,slice} which may be printed with %d
	// etc. if that is appropriate for their element types, as well as from type
	// parameters, which are expanded to the constituents of their type set.
	//
	// The reason field may be set to report the cause of the mismatch.
	type argMatcher struct {
	t printfArgType
	seen map[types.Type]bool
	reason string
	}

	// match checks if typ matches m's printf arg type. If topLevel is true, typ is
	// the actual type of the printf arg, for which special rules apply. As a
	// special case, top level type parameters pass topLevel=true when checking for
	// matches among the constituents of their type set, as type arguments will
	// replace the type parameter at compile time.
	func (m *argMatcher) match(typ types.Type, topLevel bool) bool {
	// %w accepts only errors.
	if m.t == argError {
	return types.ConvertibleTo(typ, errorType)
	}

	// If the type implements fmt.Formatter, we have nothing to check.
	if isFormatter(typ) {
	return true
	}

	// If we can use a string, might arg (dynamically) implement the Stringer or Error interface?
	if m.t&argString != 0 && isConvertibleToString(typ) {
	return true
	}

	if typ, _ := typ.(*typeparams.TypeParam); typ != nil {
	// Avoid infinite recursion through type parameters.
	if m.seen[typ] {
	return true
	}
	m.seen[typ] = true
	terms, err := typeparams.StructuralTerms(typ)
	if err != nil {
	return true // invalid type (possibly an empty type set)
	}

	if len(terms) == 0 {
	// No restrictions on the underlying of typ. Type parameters implementing
	// error, fmt.Formatter, or fmt.Stringer were handled above, and %v and
	// %T was handled in matchType. We're about to check restrictions the
	// underlying; if the underlying type is unrestricted there must be an
	// element of the type set that violates one of the arg type checks
	// below, so we can safely return false here.

	if m.t == anyType { // anyType must have already been handled.
	panic("unexpected printfArgType")
	}
	return false
	}

	// Only report a reason if typ is the argument type, otherwise it won't
	// make sense. Note that it is not sufficient to check if topLevel == here,
	// as type parameters can have a type set consisting of other type
	// parameters.
	reportReason := len(m.seen) == 1

	for _, term := range terms {
	if !m.match(term.Type(), topLevel) {
	if reportReason {
	if term.Tilde() {
	m.reason = fmt.Sprintf("contains ~%s", term.Type())
	} else {
	m.reason = fmt.Sprintf("contains %s", term.Type())
	}
	}
	return false
	}
	}
	return true
	}

	typ = typ.Underlying()
	if m.seen[typ] {
	// We've already considered typ, or are in the process of considering it.
	// In case we've already considered typ, it must have been valid (else we
	// would have stopped matching). In case we're in the process of
	// considering it, we must avoid infinite recursion.
	//
	// There are some pathological cases where returning true here is
	// incorrect, for example `type R struct { F []R }`, but these are
	// acceptable false negatives.
	return true
	}
	m.seen[typ] = true

	switch typ := typ.(type) {
	case *types.Signature:
	return m.t == argPointer

	case *types.Map:
	if m.t == argPointer {
	return true
	}
	// Recur: map[int]int matches %d.
	return m.match(typ.Key(), false) && m.match(typ.Elem(), false)

	case *types.Chan:
	return m.t&argPointer != 0

	case *types.Array:
	// Same as slice.
	if types.Identical(typ.Elem().Underlying(), types.Typ[types.Byte]) && m.t&argString != 0 {
	return true // %s matches []byte
	}
	// Recur: []int matches %d.
	return m.match(typ.Elem(), false)

	case *types.Slice:
	// Same as array.
	if types.Identical(typ.Elem().Underlying(), types.Typ[types.Byte]) && m.t&argString != 0 {
	return true // %s matches []byte
	}
	if m.t == argPointer {
	return true // %p prints a slice's 0th element
	}
	// Recur: []int matches %d. But watch out for
	// type T []T
	// If the element is a pointer type (type T[]*T), it's handled fine by the Pointer case below.
	return m.match(typ.Elem(), false)

	case *types.Pointer:
	// Ugly, but dealing with an edge case: a known pointer to an invalid type,
	// probably something from a failed import.
	if typ.Elem() == types.Typ[types.Invalid] {
	return true // special case
	}
	// If it's actually a pointer with %p, it prints as one.
	if m.t == argPointer {
	return true
	}

	if typeparams.IsTypeParam(typ.Elem()) {
	return true // We don't know whether the logic below applies. Give up.
	}

	under := typ.Elem().Underlying()
	switch under.(type) {
	case *types.Struct: // see below
	case *types.Array: // see below
	case *types.Slice: // see below
	case *types.Map: // see below
	default:
	// Check whether the rest can print pointers.
	return m.t&argPointer != 0
	}
	// If it's a top-level pointer to a struct, array, slice, type param, or
	// map, that's equivalent in our analysis to whether we can
	// print the type being pointed to. Pointers in nested levels
	// are not supported to minimize fmt running into loops.
	if !topLevel {
	return false
	}
	return m.match(under, false)

	case *types.Struct:
	// report whether all the elements of the struct match the expected type. For
	// instance, with "%d" all the elements must be printable with the "%d" format.
	for i := 0; i < typ.NumFields(); i++ {
	typf := typ.Field(i)
	if !m.match(typf.Type(), false) {
	return false
	}
	if m.t&argString != 0 && !typf.Exported() && isConvertibleToString(typf.Type()) {
	// Issue #17798: unexported Stringer or error cannot be properly formatted.
	return false
	}
	}
	return true

	case *types.Interface:
	// There's little we can do.
	// Whether any particular verb is valid depends on the argument.
	// The user may have reasonable prior knowledge of the contents of the interface.
	return true

	case *types.Basic:
	switch typ.Kind() {
	case types.UntypedBool,
	types.Bool:
	return m.t&argBool != 0

	case types.UntypedInt,
	types.Int,
	types.Int8,
	types.Int16,
	types.Int32,
	types.Int64,
	types.Uint,
	types.Uint8,
	types.Uint16,
	types.Uint32,
	types.Uint64,
	types.Uintptr:
	return m.t&argInt != 0

	case types.UntypedFloat,
	types.Float32,
	types.Float64:
	return m.t&argFloat != 0

	case types.UntypedComplex,
	types.Complex64,
	types.Complex128:
	return m.t&argComplex != 0

	case types.UntypedString,
	types.String:
	return m.t&argString != 0

	case types.UnsafePointer:
	return m.t&(argPointer\|argInt) != 0

	case types.UntypedRune:
	return m.t&(argInt\|argRune) != 0

	case types.UntypedNil:
	return false

	case types.Invalid:
	return true // Probably a type check problem.
	}
	panic("unreachable")
	}

	return false
	}

	func isConvertibleToString(typ types.Type) bool {
	if bt, ok := typ.(*types.Basic); ok && bt.Kind() == types.UntypedNil {
	// We explicitly don't want untyped nil, which is
	// convertible to both of the interfaces below, as it
	// would just panic anyway.
	return false
	}
	if types.ConvertibleTo(typ, errorType) {
	return true // via .Error()
	}

	// Does it implement fmt.Stringer?
	if obj, _, _ := types.LookupFieldOrMethod(typ, false, nil, "String"); obj != nil {
	if fn, ok := obj.(*types.Func); ok {
	sig := fn.Type().(*types.Signature)
	if sig.Params().Len() == 0 &&
	sig.Results().Len() == 1 &&
	sig.Results().At(0).Type() == types.Typ[types.String] {
	return true
	}
	}
	}

	return false
	}