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| Current File : //opt/golang/1.22.0/src/cmd/compile/internal/types2/call.go |
// 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.
// This file implements typechecking of call and selector expressions.
package types2
import (
"cmd/compile/internal/syntax"
. "internal/types/errors"
"strings"
"unicode"
)
// funcInst type-checks a function instantiation.
// The incoming x must be a generic function.
// If inst != nil, it provides some or all of the type arguments (inst.Index).
// If target != nil, it may be used to infer missing type arguments of x, if any.
// At least one of T or inst must be provided.
//
// There are two modes of operation:
//
// 1. If infer == true, funcInst infers missing type arguments as needed and
// instantiates the function x. The returned results are nil.
//
// 2. If infer == false and inst provides all type arguments, funcInst
// instantiates the function x. The returned results are nil.
// If inst doesn't provide enough type arguments, funcInst returns the
// available arguments and the corresponding expression list; x remains
// unchanged.
//
// If an error (other than a version error) occurs in any case, it is reported
// and x.mode is set to invalid.
func (check *Checker) funcInst(T *target, pos syntax.Pos, x *operand, inst *syntax.IndexExpr, infer bool) ([]Type, []syntax.Expr) {
assert(T != nil || inst != nil)
var instErrPos poser
if inst != nil {
instErrPos = inst.Pos()
} else {
instErrPos = pos
}
versionErr := !check.verifyVersionf(instErrPos, go1_18, "function instantiation")
// targs and xlist are the type arguments and corresponding type expressions, or nil.
var targs []Type
var xlist []syntax.Expr
if inst != nil {
xlist = syntax.UnpackListExpr(inst.Index)
targs = check.typeList(xlist)
if targs == nil {
x.mode = invalid
x.expr = inst
return nil, nil
}
assert(len(targs) == len(xlist))
}
// Check the number of type arguments (got) vs number of type parameters (want).
// Note that x is a function value, not a type expression, so we don't need to
// call under below.
sig := x.typ.(*Signature)
got, want := len(targs), sig.TypeParams().Len()
if got > want {
// Providing too many type arguments is always an error.
check.errorf(xlist[got-1], WrongTypeArgCount, "got %d type arguments but want %d", got, want)
x.mode = invalid
x.expr = inst
return nil, nil
}
if got < want {
if !infer {
return targs, xlist
}
// If the uninstantiated or partially instantiated function x is used in
// an assignment (tsig != nil), infer missing type arguments by treating
// the assignment
//
// var tvar tsig = x
//
// like a call g(tvar) of the synthetic generic function g
//
// func g[type_parameters_of_x](func_type_of_x)
//
var args []*operand
var params []*Var
var reverse bool
if T != nil && sig.tparams != nil {
if !versionErr && !check.allowVersion(check.pkg, instErrPos, go1_21) {
if inst != nil {
check.versionErrorf(instErrPos, go1_21, "partially instantiated function in assignment")
} else {
check.versionErrorf(instErrPos, go1_21, "implicitly instantiated function in assignment")
}
}
gsig := NewSignatureType(nil, nil, nil, sig.params, sig.results, sig.variadic)
params = []*Var{NewVar(x.Pos(), check.pkg, "", gsig)}
// The type of the argument operand is tsig, which is the type of the LHS in an assignment
// or the result type in a return statement. Create a pseudo-expression for that operand
// that makes sense when reported in error messages from infer, below.
expr := syntax.NewName(x.Pos(), T.desc)
args = []*operand{{mode: value, expr: expr, typ: T.sig}}
reverse = true
}
// Rename type parameters to avoid problems with recursive instantiations.
// Note that NewTuple(params...) below is (*Tuple)(nil) if len(params) == 0, as desired.
tparams, params2 := check.renameTParams(pos, sig.TypeParams().list(), NewTuple(params...))
targs = check.infer(pos, tparams, targs, params2.(*Tuple), args, reverse)
if targs == nil {
// error was already reported
x.mode = invalid
x.expr = inst
return nil, nil
}
got = len(targs)
}
assert(got == want)
// instantiate function signature
expr := x.expr // if we don't have an index expression, keep the existing expression of x
if inst != nil {
expr = inst
}
sig = check.instantiateSignature(x.Pos(), expr, sig, targs, xlist)
x.typ = sig
x.mode = value
x.expr = expr
return nil, nil
}
func (check *Checker) instantiateSignature(pos syntax.Pos, expr syntax.Expr, typ *Signature, targs []Type, xlist []syntax.Expr) (res *Signature) {
assert(check != nil)
assert(len(targs) == typ.TypeParams().Len())
if check.conf.Trace {
check.trace(pos, "-- instantiating signature %s with %s", typ, targs)
check.indent++
defer func() {
check.indent--
check.trace(pos, "=> %s (under = %s)", res, res.Underlying())
}()
}
inst := check.instance(pos, typ, targs, nil, check.context()).(*Signature)
assert(inst.TypeParams().Len() == 0) // signature is not generic anymore
check.recordInstance(expr, targs, inst)
assert(len(xlist) <= len(targs))
// verify instantiation lazily (was go.dev/issue/50450)
check.later(func() {
tparams := typ.TypeParams().list()
if i, err := check.verify(pos, tparams, targs, check.context()); err != nil {
// best position for error reporting
pos := pos
if i < len(xlist) {
pos = syntax.StartPos(xlist[i])
}
check.softErrorf(pos, InvalidTypeArg, "%s", err)
} else {
check.mono.recordInstance(check.pkg, pos, tparams, targs, xlist)
}
}).describef(pos, "verify instantiation")
return inst
}
func (check *Checker) callExpr(x *operand, call *syntax.CallExpr) exprKind {
var inst *syntax.IndexExpr // function instantiation, if any
if iexpr, _ := call.Fun.(*syntax.IndexExpr); iexpr != nil {
if check.indexExpr(x, iexpr) {
// Delay function instantiation to argument checking,
// where we combine type and value arguments for type
// inference.
assert(x.mode == value)
inst = iexpr
}
x.expr = iexpr
check.record(x)
} else {
check.exprOrType(x, call.Fun, true)
}
// x.typ may be generic
switch x.mode {
case invalid:
check.use(call.ArgList...)
x.expr = call
return statement
case typexpr:
// conversion
check.nonGeneric(nil, x)
if x.mode == invalid {
return conversion
}
T := x.typ
x.mode = invalid
switch n := len(call.ArgList); n {
case 0:
check.errorf(call, WrongArgCount, "missing argument in conversion to %s", T)
case 1:
check.expr(nil, x, call.ArgList[0])
if x.mode != invalid {
if t, _ := under(T).(*Interface); t != nil && !isTypeParam(T) {
if !t.IsMethodSet() {
check.errorf(call, MisplacedConstraintIface, "cannot use interface %s in conversion (contains specific type constraints or is comparable)", T)
break
}
}
if call.HasDots {
check.errorf(call.ArgList[0], BadDotDotDotSyntax, "invalid use of ... in conversion to %s", T)
break
}
check.conversion(x, T)
}
default:
check.use(call.ArgList...)
check.errorf(call.ArgList[n-1], WrongArgCount, "too many arguments in conversion to %s", T)
}
x.expr = call
return conversion
case builtin:
// no need to check for non-genericity here
id := x.id
if !check.builtin(x, call, id) {
x.mode = invalid
}
x.expr = call
// a non-constant result implies a function call
if x.mode != invalid && x.mode != constant_ {
check.hasCallOrRecv = true
}
return predeclaredFuncs[id].kind
}
// ordinary function/method call
// signature may be generic
cgocall := x.mode == cgofunc
// a type parameter may be "called" if all types have the same signature
sig, _ := coreType(x.typ).(*Signature)
if sig == nil {
check.errorf(x, InvalidCall, invalidOp+"cannot call non-function %s", x)
x.mode = invalid
x.expr = call
return statement
}
// Capture wasGeneric before sig is potentially instantiated below.
wasGeneric := sig.TypeParams().Len() > 0
// evaluate type arguments, if any
var xlist []syntax.Expr
var targs []Type
if inst != nil {
xlist = syntax.UnpackListExpr(inst.Index)
targs = check.typeList(xlist)
if targs == nil {
check.use(call.ArgList...)
x.mode = invalid
x.expr = call
return statement
}
assert(len(targs) == len(xlist))
// check number of type arguments (got) vs number of type parameters (want)
got, want := len(targs), sig.TypeParams().Len()
if got > want {
check.errorf(xlist[want], WrongTypeArgCount, "got %d type arguments but want %d", got, want)
check.use(call.ArgList...)
x.mode = invalid
x.expr = call
return statement
}
// If sig is generic and all type arguments are provided, preempt function
// argument type inference by explicitly instantiating the signature. This
// ensures that we record accurate type information for sig, even if there
// is an error checking its arguments (for example, if an incorrect number
// of arguments is supplied).
if got == want && want > 0 {
check.verifyVersionf(inst, go1_18, "function instantiation")
sig = check.instantiateSignature(inst.Pos(), inst, sig, targs, xlist)
// targs have been consumed; proceed with checking arguments of the
// non-generic signature.
targs = nil
xlist = nil
}
}
// evaluate arguments
args, atargs, atxlist := check.genericExprList(call.ArgList)
sig = check.arguments(call, sig, targs, xlist, args, atargs, atxlist)
if wasGeneric && sig.TypeParams().Len() == 0 {
// update the recorded type of call.Fun to its instantiated type
check.recordTypeAndValue(call.Fun, value, sig, nil)
}
// determine result
switch sig.results.Len() {
case 0:
x.mode = novalue
case 1:
if cgocall {
x.mode = commaerr
} else {
x.mode = value
}
x.typ = sig.results.vars[0].typ // unpack tuple
default:
x.mode = value
x.typ = sig.results
}
x.expr = call
check.hasCallOrRecv = true
// if type inference failed, a parameterized result must be invalidated
// (operands cannot have a parameterized type)
if x.mode == value && sig.TypeParams().Len() > 0 && isParameterized(sig.TypeParams().list(), x.typ) {
x.mode = invalid
}
return statement
}
// exprList evaluates a list of expressions and returns the corresponding operands.
// A single-element expression list may evaluate to multiple operands.
func (check *Checker) exprList(elist []syntax.Expr) (xlist []*operand) {
if n := len(elist); n == 1 {
xlist, _ = check.multiExpr(elist[0], false)
} else if n > 1 {
// multiple (possibly invalid) values
xlist = make([]*operand, n)
for i, e := range elist {
var x operand
check.expr(nil, &x, e)
xlist[i] = &x
}
}
return
}
// genericExprList is like exprList but result operands may be uninstantiated or partially
// instantiated generic functions (where constraint information is insufficient to infer
// the missing type arguments) for Go 1.21 and later.
// For each non-generic or uninstantiated generic operand, the corresponding targsList and
// xlistList elements do not exist (targsList and xlistList are nil) or the elements are nil.
// For each partially instantiated generic function operand, the corresponding targsList and
// xlistList elements are the operand's partial type arguments and type expression lists.
func (check *Checker) genericExprList(elist []syntax.Expr) (resList []*operand, targsList [][]Type, xlistList [][]syntax.Expr) {
if debug {
defer func() {
// targsList and xlistList must have matching lengths
assert(len(targsList) == len(xlistList))
// type arguments must only exist for partially instantiated functions
for i, x := range resList {
if i < len(targsList) {
if n := len(targsList[i]); n > 0 {
// x must be a partially instantiated function
assert(n < x.typ.(*Signature).TypeParams().Len())
}
}
}
}()
}
// Before Go 1.21, uninstantiated or partially instantiated argument functions are
// nor permitted. Checker.funcInst must infer missing type arguments in that case.
infer := true // for -lang < go1.21
n := len(elist)
if n > 0 && check.allowVersion(check.pkg, elist[0], go1_21) {
infer = false
}
if n == 1 {
// single value (possibly a partially instantiated function), or a multi-valued expression
e := elist[0]
var x operand
if inst, _ := e.(*syntax.IndexExpr); inst != nil && check.indexExpr(&x, inst) {
// x is a generic function.
targs, xlist := check.funcInst(nil, x.Pos(), &x, inst, infer)
if targs != nil {
// x was not instantiated: collect the (partial) type arguments.
targsList = [][]Type{targs}
xlistList = [][]syntax.Expr{xlist}
// Update x.expr so that we can record the partially instantiated function.
x.expr = inst
} else {
// x was instantiated: we must record it here because we didn't
// use the usual expression evaluators.
check.record(&x)
}
resList = []*operand{&x}
} else {
// x is not a function instantiation (it may still be a generic function).
check.rawExpr(nil, &x, e, nil, true)
check.exclude(&x, 1<<novalue|1<<builtin|1<<typexpr)
if t, ok := x.typ.(*Tuple); ok && x.mode != invalid {
// x is a function call returning multiple values; it cannot be generic.
resList = make([]*operand, t.Len())
for i, v := range t.vars {
resList[i] = &operand{mode: value, expr: e, typ: v.typ}
}
} else {
// x is exactly one value (possibly invalid or uninstantiated generic function).
resList = []*operand{&x}
}
}
} else if n > 1 {
// multiple values
resList = make([]*operand, n)
targsList = make([][]Type, n)
xlistList = make([][]syntax.Expr, n)
for i, e := range elist {
var x operand
if inst, _ := e.(*syntax.IndexExpr); inst != nil && check.indexExpr(&x, inst) {
// x is a generic function.
targs, xlist := check.funcInst(nil, x.Pos(), &x, inst, infer)
if targs != nil {
// x was not instantiated: collect the (partial) type arguments.
targsList[i] = targs
xlistList[i] = xlist
// Update x.expr so that we can record the partially instantiated function.
x.expr = inst
} else {
// x was instantiated: we must record it here because we didn't
// use the usual expression evaluators.
check.record(&x)
}
} else {
// x is exactly one value (possibly invalid or uninstantiated generic function).
check.genericExpr(&x, e)
}
resList[i] = &x
}
}
return
}
// arguments type-checks arguments passed to a function call with the given signature.
// The function and its arguments may be generic, and possibly partially instantiated.
// targs and xlist are the function's type arguments (and corresponding expressions).
// args are the function arguments. If an argument args[i] is a partially instantiated
// generic function, atargs[i] and atxlist[i] are the corresponding type arguments
// (and corresponding expressions).
// If the callee is variadic, arguments adjusts its signature to match the provided
// arguments. The type parameters and arguments of the callee and all its arguments
// are used together to infer any missing type arguments, and the callee and argument
// functions are instantiated as necessary.
// The result signature is the (possibly adjusted and instantiated) function signature.
// If an error occurred, the result signature is the incoming sig.
func (check *Checker) arguments(call *syntax.CallExpr, sig *Signature, targs []Type, xlist []syntax.Expr, args []*operand, atargs [][]Type, atxlist [][]syntax.Expr) (rsig *Signature) {
rsig = sig
// Function call argument/parameter count requirements
//
// | standard call | dotdotdot call |
// --------------+------------------+----------------+
// standard func | nargs == npars | invalid |
// --------------+------------------+----------------+
// variadic func | nargs >= npars-1 | nargs == npars |
// --------------+------------------+----------------+
nargs := len(args)
npars := sig.params.Len()
ddd := call.HasDots
// set up parameters
sigParams := sig.params // adjusted for variadic functions (may be nil for empty parameter lists!)
adjusted := false // indicates if sigParams is different from sig.params
if sig.variadic {
if ddd {
// variadic_func(a, b, c...)
if len(call.ArgList) == 1 && nargs > 1 {
// f()... is not permitted if f() is multi-valued
//check.errorf(call.Ellipsis, "cannot use ... with %d-valued %s", nargs, call.ArgList[0])
check.errorf(call, InvalidDotDotDot, "cannot use ... with %d-valued %s", nargs, call.ArgList[0])
return
}
} else {
// variadic_func(a, b, c)
if nargs >= npars-1 {
// Create custom parameters for arguments: keep
// the first npars-1 parameters and add one for
// each argument mapping to the ... parameter.
vars := make([]*Var, npars-1) // npars > 0 for variadic functions
copy(vars, sig.params.vars)
last := sig.params.vars[npars-1]
typ := last.typ.(*Slice).elem
for len(vars) < nargs {
vars = append(vars, NewParam(last.pos, last.pkg, last.name, typ))
}
sigParams = NewTuple(vars...) // possibly nil!
adjusted = true
npars = nargs
} else {
// nargs < npars-1
npars-- // for correct error message below
}
}
} else {
if ddd {
// standard_func(a, b, c...)
//check.errorf(call.Ellipsis, "cannot use ... in call to non-variadic %s", call.Fun)
check.errorf(call, NonVariadicDotDotDot, "cannot use ... in call to non-variadic %s", call.Fun)
return
}
// standard_func(a, b, c)
}
// check argument count
if nargs != npars {
var at poser = call
qualifier := "not enough"
if nargs > npars {
at = args[npars].expr // report at first extra argument
qualifier = "too many"
} else if nargs > 0 {
at = args[nargs-1].expr // report at last argument
}
// take care of empty parameter lists represented by nil tuples
var params []*Var
if sig.params != nil {
params = sig.params.vars
}
var err error_
err.code = WrongArgCount
err.errorf(at, "%s arguments in call to %s", qualifier, call.Fun)
err.errorf(nopos, "have %s", check.typesSummary(operandTypes(args), false))
err.errorf(nopos, "want %s", check.typesSummary(varTypes(params), sig.variadic))
check.report(&err)
return
}
// collect type parameters of callee and generic function arguments
var tparams []*TypeParam
// collect type parameters of callee
n := sig.TypeParams().Len()
if n > 0 {
if !check.allowVersion(check.pkg, call.Pos(), go1_18) {
if iexpr, _ := call.Fun.(*syntax.IndexExpr); iexpr != nil {
check.versionErrorf(iexpr, go1_18, "function instantiation")
} else {
check.versionErrorf(call, go1_18, "implicit function instantiation")
}
}
// rename type parameters to avoid problems with recursive calls
var tmp Type
tparams, tmp = check.renameTParams(call.Pos(), sig.TypeParams().list(), sigParams)
sigParams = tmp.(*Tuple)
// make sure targs and tparams have the same length
for len(targs) < len(tparams) {
targs = append(targs, nil)
}
}
assert(len(tparams) == len(targs))
// collect type parameters from generic function arguments
var genericArgs []int // indices of generic function arguments
if enableReverseTypeInference {
for i, arg := range args {
// generic arguments cannot have a defined (*Named) type - no need for underlying type below
if asig, _ := arg.typ.(*Signature); asig != nil && asig.TypeParams().Len() > 0 {
// The argument type is a generic function signature. This type is
// pointer-identical with (it's copied from) the type of the generic
// function argument and thus the function object.
// Before we change the type (type parameter renaming, below), make
// a clone of it as otherwise we implicitly modify the object's type
// (go.dev/issues/63260).
asig = clone(asig)
// Rename type parameters for cases like f(g, g); this gives each
// generic function argument a unique type identity (go.dev/issues/59956).
// TODO(gri) Consider only doing this if a function argument appears
// multiple times, which is rare (possible optimization).
atparams, tmp := check.renameTParams(call.Pos(), asig.TypeParams().list(), asig)
asig = tmp.(*Signature)
asig.tparams = &TypeParamList{atparams} // renameTParams doesn't touch associated type parameters
arg.typ = asig // new type identity for the function argument
tparams = append(tparams, atparams...)
// add partial list of type arguments, if any
if i < len(atargs) {
targs = append(targs, atargs[i]...)
}
// make sure targs and tparams have the same length
for len(targs) < len(tparams) {
targs = append(targs, nil)
}
genericArgs = append(genericArgs, i)
}
}
}
assert(len(tparams) == len(targs))
// at the moment we only support implicit instantiations of argument functions
_ = len(genericArgs) > 0 && check.verifyVersionf(args[genericArgs[0]], go1_21, "implicitly instantiated function as argument")
// tparams holds the type parameters of the callee and generic function arguments, if any:
// the first n type parameters belong to the callee, followed by mi type parameters for each
// of the generic function arguments, where mi = args[i].typ.(*Signature).TypeParams().Len().
// infer missing type arguments of callee and function arguments
if len(tparams) > 0 {
targs = check.infer(call.Pos(), tparams, targs, sigParams, args, false)
if targs == nil {
// TODO(gri) If infer inferred the first targs[:n], consider instantiating
// the call signature for better error messages/gopls behavior.
// Perhaps instantiate as much as we can, also for arguments.
// This will require changes to how infer returns its results.
return // error already reported
}
// update result signature: instantiate if needed
if n > 0 {
rsig = check.instantiateSignature(call.Pos(), call.Fun, sig, targs[:n], xlist)
// If the callee's parameter list was adjusted we need to update (instantiate)
// it separately. Otherwise we can simply use the result signature's parameter
// list.
if adjusted {
sigParams = check.subst(call.Pos(), sigParams, makeSubstMap(tparams[:n], targs[:n]), nil, check.context()).(*Tuple)
} else {
sigParams = rsig.params
}
}
// compute argument signatures: instantiate if needed
j := n
for _, i := range genericArgs {
arg := args[i]
asig := arg.typ.(*Signature)
k := j + asig.TypeParams().Len()
// targs[j:k] are the inferred type arguments for asig
arg.typ = check.instantiateSignature(call.Pos(), arg.expr, asig, targs[j:k], nil) // TODO(gri) provide xlist if possible (partial instantiations)
check.record(arg) // record here because we didn't use the usual expr evaluators
j = k
}
}
// check arguments
if len(args) > 0 {
context := check.sprintf("argument to %s", call.Fun)
for i, a := range args {
check.assignment(a, sigParams.vars[i].typ, context)
}
}
return
}
var cgoPrefixes = [...]string{
"_Ciconst_",
"_Cfconst_",
"_Csconst_",
"_Ctype_",
"_Cvar_", // actually a pointer to the var
"_Cfpvar_fp_",
"_Cfunc_",
"_Cmacro_", // function to evaluate the expanded expression
}
func (check *Checker) selector(x *operand, e *syntax.SelectorExpr, def *TypeName, wantType bool) {
// these must be declared before the "goto Error" statements
var (
obj Object
index []int
indirect bool
)
sel := e.Sel.Value
// If the identifier refers to a package, handle everything here
// so we don't need a "package" mode for operands: package names
// can only appear in qualified identifiers which are mapped to
// selector expressions.
if ident, ok := e.X.(*syntax.Name); ok {
obj := check.lookup(ident.Value)
if pname, _ := obj.(*PkgName); pname != nil {
assert(pname.pkg == check.pkg)
check.recordUse(ident, pname)
pname.used = true
pkg := pname.imported
var exp Object
funcMode := value
if pkg.cgo {
// cgo special cases C.malloc: it's
// rewritten to _CMalloc and does not
// support two-result calls.
if sel == "malloc" {
sel = "_CMalloc"
} else {
funcMode = cgofunc
}
for _, prefix := range cgoPrefixes {
// cgo objects are part of the current package (in file
// _cgo_gotypes.go). Use regular lookup.
_, exp = check.scope.LookupParent(prefix+sel, check.pos)
if exp != nil {
break
}
}
if exp == nil {
check.errorf(e.Sel, UndeclaredImportedName, "undefined: %s", syntax.Expr(e)) // cast to syntax.Expr to silence vet
goto Error
}
check.objDecl(exp, nil)
} else {
exp = pkg.scope.Lookup(sel)
if exp == nil {
if !pkg.fake {
check.errorf(e.Sel, UndeclaredImportedName, "undefined: %s", syntax.Expr(e))
}
goto Error
}
if !exp.Exported() {
check.errorf(e.Sel, UnexportedName, "%s not exported by package %s", sel, pkg.name)
// ok to continue
}
}
check.recordUse(e.Sel, exp)
// Simplified version of the code for *syntax.Names:
// - imported objects are always fully initialized
switch exp := exp.(type) {
case *Const:
assert(exp.Val() != nil)
x.mode = constant_
x.typ = exp.typ
x.val = exp.val
case *TypeName:
x.mode = typexpr
x.typ = exp.typ
case *Var:
x.mode = variable
x.typ = exp.typ
if pkg.cgo && strings.HasPrefix(exp.name, "_Cvar_") {
x.typ = x.typ.(*Pointer).base
}
case *Func:
x.mode = funcMode
x.typ = exp.typ
if pkg.cgo && strings.HasPrefix(exp.name, "_Cmacro_") {
x.mode = value
x.typ = x.typ.(*Signature).results.vars[0].typ
}
case *Builtin:
x.mode = builtin
x.typ = exp.typ
x.id = exp.id
default:
check.dump("%v: unexpected object %v", atPos(e.Sel), exp)
unreachable()
}
x.expr = e
return
}
}
check.exprOrType(x, e.X, false)
switch x.mode {
case typexpr:
// don't crash for "type T T.x" (was go.dev/issue/51509)
if def != nil && def.typ == x.typ {
check.cycleError([]Object{def})
goto Error
}
case builtin:
check.errorf(e.Pos(), UncalledBuiltin, "cannot select on %s", x)
goto Error
case invalid:
goto Error
}
// Avoid crashing when checking an invalid selector in a method declaration
// (i.e., where def is not set):
//
// type S[T any] struct{}
// type V = S[any]
// func (fs *S[T]) M(x V.M) {}
//
// All codepaths below return a non-type expression. If we get here while
// expecting a type expression, it is an error.
//
// See go.dev/issue/57522 for more details.
//
// TODO(rfindley): We should do better by refusing to check selectors in all cases where
// x.typ is incomplete.
if wantType {
check.errorf(e.Sel, NotAType, "%s is not a type", syntax.Expr(e))
goto Error
}
obj, index, indirect = LookupFieldOrMethod(x.typ, x.mode == variable, check.pkg, sel)
if obj == nil {
// Don't report another error if the underlying type was invalid (go.dev/issue/49541).
if !isValid(under(x.typ)) {
goto Error
}
if index != nil {
// TODO(gri) should provide actual type where the conflict happens
check.errorf(e.Sel, AmbiguousSelector, "ambiguous selector %s.%s", x.expr, sel)
goto Error
}
if indirect {
if x.mode == typexpr {
check.errorf(e.Sel, InvalidMethodExpr, "invalid method expression %s.%s (needs pointer receiver (*%s).%s)", x.typ, sel, x.typ, sel)
} else {
check.errorf(e.Sel, InvalidMethodExpr, "cannot call pointer method %s on %s", sel, x.typ)
}
goto Error
}
var why string
if isInterfacePtr(x.typ) {
why = check.interfacePtrError(x.typ)
} else {
why = check.sprintf("type %s has no field or method %s", x.typ, sel)
// Check if capitalization of sel matters and provide better error message in that case.
// TODO(gri) This code only looks at the first character but LookupFieldOrMethod has an
// (internal) mechanism for case-insensitive lookup. Should use that instead.
if len(sel) > 0 {
var changeCase string
if r := rune(sel[0]); unicode.IsUpper(r) {
changeCase = string(unicode.ToLower(r)) + sel[1:]
} else {
changeCase = string(unicode.ToUpper(r)) + sel[1:]
}
if obj, _, _ = LookupFieldOrMethod(x.typ, x.mode == variable, check.pkg, changeCase); obj != nil {
why += ", but does have " + changeCase
}
}
}
check.errorf(e.Sel, MissingFieldOrMethod, "%s.%s undefined (%s)", x.expr, sel, why)
goto Error
}
// methods may not have a fully set up signature yet
if m, _ := obj.(*Func); m != nil {
check.objDecl(m, nil)
}
if x.mode == typexpr {
// method expression
m, _ := obj.(*Func)
if m == nil {
// TODO(gri) should check if capitalization of sel matters and provide better error message in that case
check.errorf(e.Sel, MissingFieldOrMethod, "%s.%s undefined (type %s has no method %s)", x.expr, sel, x.typ, sel)
goto Error
}
check.recordSelection(e, MethodExpr, x.typ, m, index, indirect)
sig := m.typ.(*Signature)
if sig.recv == nil {
check.error(e, InvalidDeclCycle, "illegal cycle in method declaration")
goto Error
}
// The receiver type becomes the type of the first function
// argument of the method expression's function type.
var params []*Var
if sig.params != nil {
params = sig.params.vars
}
// Be consistent about named/unnamed parameters. This is not needed
// for type-checking, but the newly constructed signature may appear
// in an error message and then have mixed named/unnamed parameters.
// (An alternative would be to not print parameter names in errors,
// but it's useful to see them; this is cheap and method expressions
// are rare.)
name := ""
if len(params) > 0 && params[0].name != "" {
// name needed
name = sig.recv.name
if name == "" {
name = "_"
}
}
params = append([]*Var{NewVar(sig.recv.pos, sig.recv.pkg, name, x.typ)}, params...)
x.mode = value
x.typ = &Signature{
tparams: sig.tparams,
params: NewTuple(params...),
results: sig.results,
variadic: sig.variadic,
}
check.addDeclDep(m)
} else {
// regular selector
switch obj := obj.(type) {
case *Var:
check.recordSelection(e, FieldVal, x.typ, obj, index, indirect)
if x.mode == variable || indirect {
x.mode = variable
} else {
x.mode = value
}
x.typ = obj.typ
case *Func:
// TODO(gri) If we needed to take into account the receiver's
// addressability, should we report the type &(x.typ) instead?
check.recordSelection(e, MethodVal, x.typ, obj, index, indirect)
x.mode = value
// remove receiver
sig := *obj.typ.(*Signature)
sig.recv = nil
x.typ = &sig
check.addDeclDep(obj)
default:
unreachable()
}
}
// everything went well
x.expr = e
return
Error:
x.mode = invalid
x.expr = e
}
// use type-checks each argument.
// Useful to make sure expressions are evaluated
// (and variables are "used") in the presence of
// other errors. Arguments may be nil.
// Reports if all arguments evaluated without error.
func (check *Checker) use(args ...syntax.Expr) bool { return check.useN(args, false) }
// useLHS is like use, but doesn't "use" top-level identifiers.
// It should be called instead of use if the arguments are
// expressions on the lhs of an assignment.
func (check *Checker) useLHS(args ...syntax.Expr) bool { return check.useN(args, true) }
func (check *Checker) useN(args []syntax.Expr, lhs bool) bool {
ok := true
for _, e := range args {
if !check.use1(e, lhs) {
ok = false
}
}
return ok
}
func (check *Checker) use1(e syntax.Expr, lhs bool) bool {
var x operand
x.mode = value // anything but invalid
switch n := syntax.Unparen(e).(type) {
case nil:
// nothing to do
case *syntax.Name:
// don't report an error evaluating blank
if n.Value == "_" {
break
}
// If the lhs is an identifier denoting a variable v, this assignment
// is not a 'use' of v. Remember current value of v.used and restore
// after evaluating the lhs via check.rawExpr.
var v *Var
var v_used bool
if lhs {
if _, obj := check.scope.LookupParent(n.Value, nopos); obj != nil {
// It's ok to mark non-local variables, but ignore variables
// from other packages to avoid potential race conditions with
// dot-imported variables.
if w, _ := obj.(*Var); w != nil && w.pkg == check.pkg {
v = w
v_used = v.used
}
}
}
check.exprOrType(&x, n, true)
if v != nil {
v.used = v_used // restore v.used
}
case *syntax.ListExpr:
return check.useN(n.ElemList, lhs)
default:
check.rawExpr(nil, &x, e, nil, true)
}
return x.mode != invalid
}