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// Copyright 2013 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 ssa
// This file defines utilities for population of method sets.
import (
"fmt"
"go/types"
"golang.org/x/tools/go/types/typeutil"
"golang.org/x/tools/internal/aliases"
)
// MethodValue returns the Function implementing method sel, building
// wrapper methods on demand. It returns nil if sel denotes an
// interface or generic method.
//
// Precondition: sel.Kind() == MethodVal.
//
// Thread-safe.
//
// Acquires prog.methodsMu.
func (prog *Program) MethodValue(sel *types.Selection) *Function {
if sel.Kind() != types.MethodVal {
panic(fmt.Sprintf("MethodValue(%s) kind != MethodVal", sel))
}
T := sel.Recv()
if types.IsInterface(T) {
return nil // interface method or type parameter
}
if prog.isParameterized(T) {
return nil // generic method
}
if prog.mode&LogSource != 0 {
defer logStack("MethodValue %s %v", T, sel)()
}
var b builder
m := func() *Function {
prog.methodsMu.Lock()
defer prog.methodsMu.Unlock()
// Get or create SSA method set.
mset, ok := prog.methodSets.At(T).(*methodSet)
if !ok {
mset = &methodSet{mapping: make(map[string]*Function)}
prog.methodSets.Set(T, mset)
}
// Get or create SSA method.
id := sel.Obj().Id()
fn, ok := mset.mapping[id]
if !ok {
obj := sel.Obj().(*types.Func)
needsPromotion := len(sel.Index()) > 1
needsIndirection := !isPointer(recvType(obj)) && isPointer(T)
if needsPromotion || needsIndirection {
fn = createWrapper(prog, toSelection(sel))
fn.buildshared = b.shared()
b.enqueue(fn)
} else {
fn = prog.objectMethod(obj, &b)
}
if fn.Signature.Recv() == nil {
panic(fn)
}
mset.mapping[id] = fn
} else {
b.waitForSharedFunction(fn)
}
return fn
}()
b.iterate()
return m
}
// objectMethod returns the Function for a given method symbol.
// The symbol may be an instance of a generic function. It need not
// belong to an existing SSA package created by a call to
// prog.CreatePackage.
//
// objectMethod panics if the function is not a method.
//
// Acquires prog.objectMethodsMu.
func (prog *Program) objectMethod(obj *types.Func, b *builder) *Function {
sig := obj.Type().(*types.Signature)
if sig.Recv() == nil {
panic("not a method: " + obj.String())
}
// Belongs to a created package?
if fn := prog.FuncValue(obj); fn != nil {
return fn
}
// Instantiation of generic?
if originObj := obj.Origin(); originObj != obj {
origin := prog.objectMethod(originObj, b)
assert(origin.typeparams.Len() > 0, "origin is not generic")
targs := receiverTypeArgs(obj)
return origin.instance(targs, b)
}
// Consult/update cache of methods created from types.Func.
prog.objectMethodsMu.Lock()
defer prog.objectMethodsMu.Unlock()
fn, ok := prog.objectMethods[obj]
if !ok {
fn = createFunction(prog, obj, obj.Name(), nil, nil, "")
fn.Synthetic = "from type information (on demand)"
fn.buildshared = b.shared()
b.enqueue(fn)
if prog.objectMethods == nil {
prog.objectMethods = make(map[*types.Func]*Function)
}
prog.objectMethods[obj] = fn
} else {
b.waitForSharedFunction(fn)
}
return fn
}
// LookupMethod returns the implementation of the method of type T
// identified by (pkg, name). It returns nil if the method exists but
// is an interface method or generic method, and panics if T has no such method.
func (prog *Program) LookupMethod(T types.Type, pkg *types.Package, name string) *Function {
sel := prog.MethodSets.MethodSet(T).Lookup(pkg, name)
if sel == nil {
panic(fmt.Sprintf("%s has no method %s", T, types.Id(pkg, name)))
}
return prog.MethodValue(sel)
}
// methodSet contains the (concrete) methods of a concrete type (non-interface, non-parameterized).
type methodSet struct {
mapping map[string]*Function // populated lazily
}
// RuntimeTypes returns a new unordered slice containing all types in
// the program for which a runtime type is required.
//
// A runtime type is required for any non-parameterized, non-interface
// type that is converted to an interface, or for any type (including
// interface types) derivable from one through reflection.
//
// The methods of such types may be reachable through reflection or
// interface calls even if they are never called directly.
//
// Thread-safe.
//
// Acquires prog.runtimeTypesMu.
func (prog *Program) RuntimeTypes() []types.Type {
prog.runtimeTypesMu.Lock()
defer prog.runtimeTypesMu.Unlock()
return prog.runtimeTypes.Keys()
}
// forEachReachable calls f for type T and each type reachable from
// its type through reflection.
//
// The function f must use memoization to break cycles and
// return false when the type has already been visited.
//
// TODO(adonovan): publish in typeutil and share with go/callgraph/rta.
func forEachReachable(msets *typeutil.MethodSetCache, T types.Type, f func(types.Type) bool) {
var visit func(T types.Type, skip bool)
visit = func(T types.Type, skip bool) {
if !skip {
if !f(T) {
return
}
}
// Recursion over signatures of each method.
tmset := msets.MethodSet(T)
for i := 0; i < tmset.Len(); i++ {
sig := tmset.At(i).Type().(*types.Signature)
// It is tempting to call visit(sig, false)
// but, as noted in golang.org/cl/65450043,
// the Signature.Recv field is ignored by
// types.Identical and typeutil.Map, which
// is confusing at best.
//
// More importantly, the true signature rtype
// reachable from a method using reflection
// has no receiver but an extra ordinary parameter.
// For the Read method of io.Reader we want:
// func(Reader, []byte) (int, error)
// but here sig is:
// func([]byte) (int, error)
// with .Recv = Reader (though it is hard to
// notice because it doesn't affect Signature.String
// or types.Identical).
//
// TODO(adonovan): construct and visit the correct
// non-method signature with an extra parameter
// (though since unnamed func types have no methods
// there is essentially no actual demand for this).
//
// TODO(adonovan): document whether or not it is
// safe to skip non-exported methods (as RTA does).
visit(sig.Params(), true) // skip the Tuple
visit(sig.Results(), true) // skip the Tuple
}
switch T := T.(type) {
case *aliases.Alias:
visit(aliases.Unalias(T), skip) // emulates the pre-Alias behavior
case *types.Basic:
// nop
case *types.Interface:
// nop---handled by recursion over method set.
case *types.Pointer:
visit(T.Elem(), false)
case *types.Slice:
visit(T.Elem(), false)
case *types.Chan:
visit(T.Elem(), false)
case *types.Map:
visit(T.Key(), false)
visit(T.Elem(), false)
case *types.Signature:
if T.Recv() != nil {
panic(fmt.Sprintf("Signature %s has Recv %s", T, T.Recv()))
}
visit(T.Params(), true) // skip the Tuple
visit(T.Results(), true) // skip the Tuple
case *types.Named:
// A pointer-to-named type can be derived from a named
// type via reflection. It may have methods too.
visit(types.NewPointer(T), false)
// Consider 'type T struct{S}' where S has methods.
// Reflection provides no way to get from T to struct{S},
// only to S, so the method set of struct{S} is unwanted,
// so set 'skip' flag during recursion.
visit(T.Underlying(), true) // skip the unnamed type
case *types.Array:
visit(T.Elem(), false)
case *types.Struct:
for i, n := 0, T.NumFields(); i < n; i++ {
// TODO(adonovan): document whether or not
// it is safe to skip non-exported fields.
visit(T.Field(i).Type(), false)
}
case *types.Tuple:
for i, n := 0, T.Len(); i < n; i++ {
visit(T.At(i).Type(), false)
}
case *types.TypeParam, *types.Union:
// forEachReachable must not be called on parameterized types.
panic(T)
default:
panic(T)
}
}
visit(T, false)
}
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