go call 源码
golang call 代码
文件路径：/src/go/types/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 types
import (
"go/ast"
"go/internal/typeparams"
"go/token"
"strings"
"unicode"
)
// funcInst type-checks a function instantiation inst and returns the result in x.
// The operand x must be the evaluation of inst.X and its type must be a signature.
func (check *Checker) funcInst(x *operand, ix *typeparams.IndexExpr) {
if !check.allowVersion(check.pkg, 1, 18) {
check.softErrorf(inNode(ix.Orig, ix.Lbrack), _UnsupportedFeature, "function instantiation requires go1.18 or later")
}
targs := check.typeList(ix.Indices)
if targs == nil {
x.mode = invalid
x.expr = ix.Orig
return
}
assert(len(targs) == len(ix.Indices))
// check number of type arguments (got) vs number of type parameters (want)
sig := x.typ.(*Signature)
got, want := len(targs), sig.TypeParams().Len()
if got > want {
check.errorf(ix.Indices[got-1], _WrongTypeArgCount, "got %d type arguments but want %d", got, want)
x.mode = invalid
x.expr = ix.Orig
return
}
if got < want {
targs = check.infer(ix.Orig, sig.TypeParams().list(), targs, nil, nil)
if targs == nil {
// error was already reported
x.mode = invalid
x.expr = ix.Orig
return
}
got = len(targs)
}
assert(got == want)
// instantiate function signature
res := check.instantiateSignature(x.Pos(), sig, targs, ix.Indices)
assert(res.TypeParams().Len() == 0) // signature is not generic anymore
check.recordInstance(ix.Orig, targs, res)
x.typ = res
x.mode = value
x.expr = ix.Orig
}
func (check *Checker) instantiateSignature(pos token.Pos, typ *Signature, targs []Type, xlist []ast.Expr) (res *Signature) {
assert(check != nil)
assert(len(targs) == typ.TypeParams().Len())
if 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(len(xlist) <= len(targs))
// verify instantiation lazily (was 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 = xlist[i].Pos()
}
check.softErrorf(atPos(pos), _InvalidTypeArg, "%s", err)
} else {
check.mono.recordInstance(check.pkg, pos, tparams, targs, xlist)
}
}).describef(atPos(pos), "verify instantiation")
return inst
}
func (check *Checker) callExpr(x *operand, call *ast.CallExpr) exprKind {
ix := typeparams.UnpackIndexExpr(call.Fun)
if ix != nil {
if check.indexExpr(x, ix) {
// Delay function instantiation to argument checking,
// where we combine type and value arguments for type
// inference.
assert(x.mode == value)
} else {
ix = nil
}
x.expr = call.Fun
check.record(x)
} else {
check.exprOrType(x, call.Fun, true)
}
// x.typ may be generic
switch x.mode {
case invalid:
check.use(call.Args...)
x.expr = call
return statement
case typexpr:
// conversion
check.nonGeneric(x)
if x.mode == invalid {
return conversion
}
T := x.typ
x.mode = invalid
switch n := len(call.Args); n {
case 0:
check.errorf(inNode(call, call.Rparen), _WrongArgCount, "missing argument in conversion to %s", T)
case 1:
check.expr(x, call.Args[0])
if x.mode != invalid {
if call.Ellipsis.IsValid() {
check.errorf(call.Args[0], _BadDotDotDotSyntax, "invalid use of ... in conversion to %s", T)
break
}
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
}
}
check.conversion(x, T)
}
default:
check.use(call.Args...)
check.errorf(call.Args[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.invalidOp(x, _InvalidCall, "cannot call non-function %s", x)
x.mode = invalid
x.expr = call
return statement
}
// evaluate type arguments, if any
var xlist []ast.Expr
var targs []Type
if ix != nil {
xlist = ix.Indices
targs = check.typeList(xlist)
if targs == nil {
check.use(call.Args...)
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.Args...)
x.mode = invalid
x.expr = call
return statement
}
}
// evaluate arguments
args, _ := check.exprList(call.Args, false)
isGeneric := sig.TypeParams().Len() > 0
sig = check.arguments(call, sig, targs, args, xlist)
if isGeneric && 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 parametrized result must be invalidated
// (operands cannot have a parametrized type)
if x.mode == value && sig.TypeParams().Len() > 0 && isParameterized(sig.TypeParams().list(), x.typ) {
x.mode = invalid
}
return statement
}
func (check *Checker) exprList(elist []ast.Expr, allowCommaOk bool) (xlist []*operand, commaOk bool) {
switch len(elist) {
case 0:
// nothing to do
case 1:
// single (possibly comma-ok) value, or function returning multiple values
e := elist[0]
var x operand
check.multiExpr(&x, e)
if t, ok := x.typ.(*Tuple); ok && x.mode != invalid {
// multiple values
xlist = make([]*operand, t.Len())
for i, v := range t.vars {
xlist[i] = &operand{mode: value, expr: e, typ: v.typ}
}
break
}
// exactly one (possibly invalid or comma-ok) value
xlist = []*operand{&x}
if allowCommaOk && (x.mode == mapindex || x.mode == commaok || x.mode == commaerr) {
x2 := &operand{mode: value, expr: e, typ: Typ[UntypedBool]}
if x.mode == commaerr {
x2.typ = universeError
}
xlist = append(xlist, x2)
commaOk = true
}
default:
// multiple (possibly invalid) values
xlist = make([]*operand, len(elist))
for i, e := range elist {
var x operand
check.expr(&x, e)
xlist[i] = &x
}
}
return
}
// xlist is the list of type argument expressions supplied in the source code.
func (check *Checker) arguments(call *ast.CallExpr, sig *Signature, targs []Type, args []*operand, xlist []ast.Expr) (rsig *Signature) {
rsig = sig
// TODO(gri) try to eliminate this extra verification loop
for _, a := range args {
switch a.mode {
case typexpr:
check.errorf(a, 0, "%s used as value", a)
return
case invalid:
return
}
}
// 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.Ellipsis.IsValid()
// 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 t.params
if sig.variadic {
if ddd {
// variadic_func(a, b, c...)
if len(call.Args) == 1 && nargs > 1 {
// f()... is not permitted if f() is multi-valued
check.errorf(inNode(call, call.Ellipsis), _InvalidDotDotDot, "cannot use ... with %d-valued %s", nargs, call.Args[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(inNode(call, call.Ellipsis), _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 positioner = call
qualifier := "not enough"
if nargs > npars {
at = args[npars].expr // report at first extra argument
qualifier = "too many"
} else {
at = atPos(call.Rparen) // report at closing )
}
// take care of empty parameter lists represented by nil tuples
var params []*Var
if sig.params != nil {
params = sig.params.vars
}
err := newErrorf(at, _WrongArgCount, "%s arguments in call to %s", qualifier, call.Fun)
err.errorf(token.NoPos, "have %s", check.typesSummary(operandTypes(args), false))
err.errorf(token.NoPos, "want %s", check.typesSummary(varTypes(params), sig.variadic))
check.report(err)
return
}
// infer type arguments and instantiate signature if necessary
if sig.TypeParams().Len() > 0 {
if !check.allowVersion(check.pkg, 1, 18) {
switch call.Fun.(type) {
case *ast.IndexExpr, *ast.IndexListExpr:
ix := typeparams.UnpackIndexExpr(call.Fun)
check.softErrorf(inNode(call.Fun, ix.Lbrack), _UnsupportedFeature, "function instantiation requires go1.18 or later")
default:
check.softErrorf(inNode(call, call.Lparen), _UnsupportedFeature, "implicit function instantiation requires go1.18 or later")
}
}
targs := check.infer(call, sig.TypeParams().list(), targs, sigParams, args)
if targs == nil {
return // error already reported
}
// compute result signature
rsig = check.instantiateSignature(call.Pos(), sig, targs, xlist)
assert(rsig.TypeParams().Len() == 0) // signature is not generic anymore
check.recordInstance(call.Fun, targs, rsig)
// Optimization: Only if the parameter list was adjusted do we
// need to compute it from the adjusted list; otherwise we can
// simply use the result signature's parameter list.
if adjusted {
sigParams = check.subst(call.Pos(), sigParams, makeSubstMap(sig.TypeParams().list(), targs), nil, check.context()).(*Tuple)
} else {
sigParams = rsig.params
}
}
// 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 *ast.SelectorExpr, def *Named) {
// these must be declared before the "goto Error" statements
var (
obj Object
index []int
indirect bool
)
sel := e.Sel.Name
// 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.(*ast.Ident); ok {
obj := check.lookup(ident.Name)
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, "%s not declared by package C", sel)
goto Error
}
check.objDecl(exp, nil)
} else {
exp = pkg.scope.Lookup(sel)
if exp == nil {
if !pkg.fake {
check.errorf(e.Sel, _UndeclaredImportedName, "%s not declared by package %s", sel, pkg.name)
}
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 *ast.Idents:
// - 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", e.Sel.Pos(), 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 issue #51509)
if def != nil && x.typ == def {
check.cycleError([]Object{def.obj})
goto Error
}
case builtin:
// types2 uses the position of '.' for the error
check.errorf(e.Sel, _UncalledBuiltin, "cannot select on %s", x)
goto Error
case invalid:
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 (issue #49541).
if under(x.typ) == Typ[Invalid] {
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 {
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 should
// have an (internal) mechanism for case-insensitive lookup that we should use
// instead (see types2).
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)
// TODO(gri) The verification pass below is disabled for now because
// method sets don't match method lookup in some cases.
// For instance, if we made a copy above when creating a
// custom method for a parameterized received type, the
// method set method doesn't match (no copy there). There
/// may be other situations.
disabled := true
if !disabled && debug {
// Verify that LookupFieldOrMethod and MethodSet.Lookup agree.
// TODO(gri) This only works because we call LookupFieldOrMethod
// _before_ calling NewMethodSet: LookupFieldOrMethod completes
// any incomplete interfaces so they are available to NewMethodSet
// (which assumes that interfaces have been completed already).
typ := x.typ
if x.mode == variable {
// If typ is not an (unnamed) pointer or an interface,
// use *typ instead, because the method set of *typ
// includes the methods of typ.
// Variables are addressable, so we can always take their
// address.
if _, ok := typ.(*Pointer); !ok && !IsInterface(typ) {
typ = &Pointer{base: typ}
}
}
// If we created a synthetic pointer type above, we will throw
// away the method set computed here after use.
// TODO(gri) Method set computation should probably always compute
// both, the value and the pointer receiver method set and represent
// them in a single structure.
// TODO(gri) Consider also using a method set cache for the lifetime
// of checker once we rely on MethodSet lookup instead of individual
// lookup.
mset := NewMethodSet(typ)
if m := mset.Lookup(check.pkg, sel); m == nil || m.obj != obj {
check.dump("%v: (%s).%v -> %s", e.Pos(), typ, obj.name, m)
check.dump("%s\n", mset)
// Caution: MethodSets are supposed to be used externally
// only (after all interface types were completed). It's
// now possible that we get here incorrectly. Not urgent
// to fix since we only run this code in debug mode.
// TODO(gri) fix this eventually.
panic("method sets and lookup don't agree")
}
}
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.
// The arguments may be nil.
func (check *Checker) use(arg ...ast.Expr) {
var x operand
for _, e := range arg {
// The nil check below is necessary since certain AST fields
// may legally be nil (e.g., the ast.SliceExpr.High field).
if e != nil {
check.rawExpr(&x, e, nil, 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.
// The arguments must not be nil.
func (check *Checker) useLHS(arg ...ast.Expr) {
var x operand
for _, e := range arg {
// 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 ident, _ := unparen(e).(*ast.Ident); ident != nil {
// never type-check the blank name on the lhs
if ident.Name == "_" {
continue
}
if _, obj := check.scope.LookupParent(ident.Name, token.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.rawExpr(&x, e, nil, false)
if v != nil {
v.used = v_used // restore v.used
}
}
}
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