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// Copyright 2022 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
import (
"fmt"
"go/ast"
"go/types"
"golang.org/x/tools/internal/typeparams"
)
// _Instances returns all of the instances generated by runtime types for this function in an unspecified order.
//
// Thread-safe.
//
// This is an experimental interface! It may change without warning.
func (prog *Program) _Instances(fn *Function) []*Function {
if fn.typeparams.Len() == 0 || len(fn.typeargs) > 0 {
return nil
}
prog.methodsMu.Lock()
defer prog.methodsMu.Unlock()
return prog.instances[fn].list()
}
// A set of instantiations of a generic function fn.
type instanceSet struct {
fn *Function // fn.typeparams.Len() > 0 and len(fn.typeargs) == 0.
instances map[*typeList]*Function // canonical type arguments to an instance.
syntax *ast.FuncDecl // fn.syntax copy for instantiating after fn is done. nil on synthetic packages.
info *types.Info // fn.pkg.info copy for building after fn is done.. nil on synthetic packages.
// TODO(taking): Consider ways to allow for clearing syntax and info when done building.
// May require a public API change as MethodValue can request these be built after prog.Build() is done.
}
func (insts *instanceSet) list() []*Function {
if insts == nil {
return nil
}
fns := make([]*Function, 0, len(insts.instances))
for _, fn := range insts.instances {
fns = append(fns, fn)
}
return fns
}
// createInstanceSet adds a new instanceSet for a generic function fn if one does not exist.
//
// Precondition: fn is a package level declaration (function or method).
//
// EXCLUSIVE_LOCKS_ACQUIRED(prog.methodMu)
func (prog *Program) createInstanceSet(fn *Function) {
assert(fn.typeparams.Len() > 0 && len(fn.typeargs) == 0, "Can only create instance sets for generic functions")
prog.methodsMu.Lock()
defer prog.methodsMu.Unlock()
syntax, _ := fn.syntax.(*ast.FuncDecl)
assert((syntax == nil) == (fn.syntax == nil), "fn.syntax is either nil or a *ast.FuncDecl")
if _, ok := prog.instances[fn]; !ok {
prog.instances[fn] = &instanceSet{
fn: fn,
syntax: syntax,
info: fn.info,
}
}
}
// needsInstance returns a Function that is the instantiation of fn with the type arguments targs.
//
// Any CREATEd instance is added to cr.
//
// EXCLUSIVE_LOCKS_ACQUIRED(prog.methodMu)
func (prog *Program) needsInstance(fn *Function, targs []types.Type, cr *creator) *Function {
prog.methodsMu.Lock()
defer prog.methodsMu.Unlock()
return prog.lookupOrCreateInstance(fn, targs, cr)
}
// lookupOrCreateInstance returns a Function that is the instantiation of fn with the type arguments targs.
//
// Any CREATEd instance is added to cr.
//
// EXCLUSIVE_LOCKS_REQUIRED(prog.methodMu)
func (prog *Program) lookupOrCreateInstance(fn *Function, targs []types.Type, cr *creator) *Function {
return prog.instances[fn].lookupOrCreate(targs, &prog.parameterized, cr)
}
// lookupOrCreate returns the instantiation of insts.fn using targs.
// If the instantiation is created, this is added to cr.
func (insts *instanceSet) lookupOrCreate(targs []types.Type, parameterized *tpWalker, cr *creator) *Function {
if insts.instances == nil {
insts.instances = make(map[*typeList]*Function)
}
fn := insts.fn
prog := fn.Prog
// canonicalize on a tuple of targs. Sig is not unique.
//
// func A[T any]() {
// var x T
// fmt.Println("%T", x)
// }
key := prog.canon.List(targs)
if inst, ok := insts.instances[key]; ok {
return inst
}
// CREATE instance/instantiation wrapper
var syntax ast.Node
if insts.syntax != nil {
syntax = insts.syntax
}
var sig *types.Signature
var obj *types.Func
if recv := fn.Signature.Recv(); recv != nil {
// method
m := fn.object.(*types.Func)
obj = prog.canon.instantiateMethod(m, targs, prog.ctxt)
sig = obj.Type().(*types.Signature)
} else {
instSig, err := typeparams.Instantiate(prog.ctxt, fn.Signature, targs, false)
if err != nil {
panic(err)
}
instance, ok := instSig.(*types.Signature)
if !ok {
panic("Instantiate of a Signature returned a non-signature")
}
obj = fn.object.(*types.Func) // instantiation does not exist yet
sig = prog.canon.Type(instance).(*types.Signature)
}
var synthetic string
var subst *subster
concrete := !parameterized.anyParameterized(targs)
if prog.mode&InstantiateGenerics != 0 && concrete {
synthetic = fmt.Sprintf("instance of %s", fn.Name())
scope := typeparams.OriginMethod(obj).Scope()
subst = makeSubster(prog.ctxt, scope, fn.typeparams, targs, false)
} else {
synthetic = fmt.Sprintf("instantiation wrapper of %s", fn.Name())
}
name := fmt.Sprintf("%s%s", fn.Name(), targs) // may not be unique
instance := &Function{
name: name,
object: obj,
Signature: sig,
Synthetic: synthetic,
syntax: syntax,
topLevelOrigin: fn,
pos: obj.Pos(),
Pkg: nil,
Prog: fn.Prog,
typeparams: fn.typeparams, // share with origin
typeargs: targs,
info: insts.info, // on synthetic packages info is nil.
subst: subst,
}
cr.Add(instance)
insts.instances[key] = instance
return instance
}
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