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// Copyright 2021 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 vta
import (
"go/types"
"golang.org/x/tools/go/ssa"
"golang.org/x/tools/internal/aliases"
"golang.org/x/tools/internal/typeparams"
)
func canAlias(n1, n2 node) bool {
return isReferenceNode(n1) && isReferenceNode(n2)
}
func isReferenceNode(n node) bool {
if _, ok := n.(nestedPtrInterface); ok {
return true
}
if _, ok := n.(nestedPtrFunction); ok {
return true
}
if _, ok := aliases.Unalias(n.Type()).(*types.Pointer); ok {
return true
}
return false
}
// hasInFlow checks if a concrete type can flow to node `n`.
// Returns yes iff the type of `n` satisfies one the following:
// 1. is an interface
// 2. is a (nested) pointer to interface (needed for, say,
// slice elements of nested pointers to interface type)
// 3. is a function type (needed for higher-order type flow)
// 4. is a (nested) pointer to function (needed for, say,
// slice elements of nested pointers to function type)
// 5. is a global Recover or Panic node
func hasInFlow(n node) bool {
if _, ok := n.(panicArg); ok {
return true
}
if _, ok := n.(recoverReturn); ok {
return true
}
t := n.Type()
if i := interfaceUnderPtr(t); i != nil {
return true
}
if f := functionUnderPtr(t); f != nil {
return true
}
return types.IsInterface(t) || isFunction(t)
}
func isFunction(t types.Type) bool {
_, ok := t.Underlying().(*types.Signature)
return ok
}
// interfaceUnderPtr checks if type `t` is a potentially nested
// pointer to interface and if yes, returns the interface type.
// Otherwise, returns nil.
func interfaceUnderPtr(t types.Type) types.Type {
seen := make(map[types.Type]bool)
var visit func(types.Type) types.Type
visit = func(t types.Type) types.Type {
if seen[t] {
return nil
}
seen[t] = true
p, ok := t.Underlying().(*types.Pointer)
if !ok {
return nil
}
if types.IsInterface(p.Elem()) {
return p.Elem()
}
return visit(p.Elem())
}
return visit(t)
}
// functionUnderPtr checks if type `t` is a potentially nested
// pointer to function type and if yes, returns the function type.
// Otherwise, returns nil.
func functionUnderPtr(t types.Type) types.Type {
seen := make(map[types.Type]bool)
var visit func(types.Type) types.Type
visit = func(t types.Type) types.Type {
if seen[t] {
return nil
}
seen[t] = true
p, ok := t.Underlying().(*types.Pointer)
if !ok {
return nil
}
if isFunction(p.Elem()) {
return p.Elem()
}
return visit(p.Elem())
}
return visit(t)
}
// sliceArrayElem returns the element type of type `t` that is
// expected to be a (pointer to) array, slice or string, consistent with
// the ssa.Index and ssa.IndexAddr instructions. Panics otherwise.
func sliceArrayElem(t types.Type) types.Type {
switch u := t.Underlying().(type) {
case *types.Pointer:
switch e := u.Elem().Underlying().(type) {
case *types.Array:
return e.Elem()
case *types.Interface:
return sliceArrayElem(e) // e is a type param with matching element types.
default:
panic(t)
}
case *types.Array:
return u.Elem()
case *types.Slice:
return u.Elem()
case *types.Basic:
return types.Typ[types.Byte]
case *types.Interface: // type param.
terms, err := typeparams.InterfaceTermSet(u)
if err != nil || len(terms) == 0 {
panic(t)
}
return sliceArrayElem(terms[0].Type()) // Element types must match.
default:
panic(t)
}
}
// siteCallees returns a go1.23 iterator for the callees for call site `c`.
func siteCallees(c ssa.CallInstruction, callees calleesFunc) func(yield func(*ssa.Function) bool) {
// TODO: when x/tools uses go1.23, change callers to use range-over-func
// (https://go.dev/issue/65237).
return func(yield func(*ssa.Function) bool) {
for _, callee := range callees(c) {
if !yield(callee) {
return
}
}
}
}
func canHaveMethods(t types.Type) bool {
t = aliases.Unalias(t)
if _, ok := t.(*types.Named); ok {
return true
}
u := t.Underlying()
switch u.(type) {
case *types.Interface, *types.Signature, *types.Struct:
return true
default:
return false
}
}
// calls returns the set of call instructions in `f`.
func calls(f *ssa.Function) []ssa.CallInstruction {
var calls []ssa.CallInstruction
for _, bl := range f.Blocks {
for _, instr := range bl.Instrs {
if c, ok := instr.(ssa.CallInstruction); ok {
calls = append(calls, c)
}
}
}
return calls
}
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