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// 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 (
"go/ast"
"go/types"
"golang.org/x/tools/go/analysis"
"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
)
var errorType = types.Universe.Lookup("error").Type().Underlying().(*types.Interface)
// matchArgType reports an error if printf verb t is not appropriate
// for operand arg.
//
// typ is used only for recursive calls; external callers must supply nil.
//
// (Recursion arises from the compound types {map,chan,slice} which
// may be printed with %d etc. if that is appropriate for their element
// types.)
func matchArgType(pass *analysis.Pass, t printfArgType, typ types.Type, arg ast.Expr) bool {
return matchArgTypeInternal(pass, t, typ, arg, make(map[types.Type]bool))
}
// matchArgTypeInternal is the internal version of matchArgType. It carries a map
// remembering what types are in progress so we don't recur when faced with recursive
// types or mutually recursive types.
func matchArgTypeInternal(pass *analysis.Pass, t printfArgType, typ types.Type, arg ast.Expr, inProgress map[types.Type]bool) bool {
// %v, %T accept any argument type.
if t == anyType {
return true
}
if typ == nil {
// external call
typ = pass.TypesInfo.Types[arg].Type
if typ == nil {
return true // probably a type check problem
}
}
// %w accepts only errors.
if 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 t&argString != 0 && isConvertibleToString(pass, typ) {
return true
}
typ = typ.Underlying()
if inProgress[typ] {
// We're already looking at this type. The call that started it will take care of it.
return true
}
inProgress[typ] = true
switch typ := typ.(type) {
case *types.Signature:
return t == argPointer
case *types.Map:
return t == argPointer ||
// Recur: map[int]int matches %d.
(matchArgTypeInternal(pass, t, typ.Key(), arg, inProgress) && matchArgTypeInternal(pass, t, typ.Elem(), arg, inProgress))
case *types.Chan:
return t&argPointer != 0
case *types.Array:
// Same as slice.
if types.Identical(typ.Elem().Underlying(), types.Typ[types.Byte]) && t&argString != 0 {
return true // %s matches []byte
}
// Recur: []int matches %d.
return matchArgTypeInternal(pass, t, typ.Elem(), arg, inProgress)
case *types.Slice:
// Same as array.
if types.Identical(typ.Elem().Underlying(), types.Typ[types.Byte]) && t&argString != 0 {
return true // %s matches []byte
}
if 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 matchArgTypeInternal(pass, t, typ.Elem(), arg, inProgress)
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().String() == "invalid type" {
if false {
pass.Reportf(arg.Pos(), "printf argument %v is pointer to invalid or unknown type", analysisutil.Format(pass.Fset, arg))
}
return true // special case
}
// If it's actually a pointer with %p, it prints as one.
if t == argPointer {
return true
}
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 t&argPointer != 0
}
// If it's a top-level pointer to a struct, array, slice, 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 len(inProgress) > 1 {
return false
}
return matchArgTypeInternal(pass, t, under, arg, inProgress)
case *types.Struct:
return matchStructArgType(pass, t, typ, arg, inProgress)
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 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 t&argInt != 0
case types.UntypedFloat,
types.Float32,
types.Float64:
return t&argFloat != 0
case types.UntypedComplex,
types.Complex64,
types.Complex128:
return t&argComplex != 0
case types.UntypedString,
types.String:
return t&argString != 0
case types.UnsafePointer:
return t&(argPointer|argInt) != 0
case types.UntypedRune:
return t&(argInt|argRune) != 0
case types.UntypedNil:
return false
case types.Invalid:
if false {
pass.Reportf(arg.Pos(), "printf argument %v has invalid or unknown type", analysisutil.Format(pass.Fset, arg))
}
return true // Probably a type check problem.
}
panic("unreachable")
}
return false
}
func isConvertibleToString(pass *analysis.Pass, 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
}
// hasBasicType reports whether x's type is a types.Basic with the given kind.
func hasBasicType(pass *analysis.Pass, x ast.Expr, kind types.BasicKind) bool {
t := pass.TypesInfo.Types[x].Type
if t != nil {
t = t.Underlying()
}
b, ok := t.(*types.Basic)
return ok && b.Kind() == kind
}
// matchStructArgType reports 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.
func matchStructArgType(pass *analysis.Pass, t printfArgType, typ *types.Struct, arg ast.Expr, inProgress map[types.Type]bool) bool {
for i := 0; i < typ.NumFields(); i++ {
typf := typ.Field(i)
if !matchArgTypeInternal(pass, t, typf.Type(), arg, inProgress) {
return false
}
if t&argString != 0 && !typf.Exported() && isConvertibleToString(pass, typf.Type()) {
// Issue #17798: unexported Stringer or error cannot be properly formatted.
return false
}
}
return true
}
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