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go/types, types2: permit partially instantiated functions as function arguments
This CL changes Checker.genericExprList such that it collects partially instantiated generic functions together with their (partial) type argument (and corresponding) expression lists, instead of trying to infer the missing type arguments in place or to report an error. Special care is being taken to explictly record expression types where needed (because we can't use one of the usual expr evaluators which takes care of that), or to track the correct instance expression for later recording with Checker.arguments. The resulting generic expression list is passed to Checker.arguments which is changed to accept explicit partial type argument (and corresponding) expression lists. The provided type arguments are fed into type inference, matching up with their respective type parameters (which were collected already, before this CL). If type inference is successful, the instantiated functions are recorded as needed. For now, the type argument expression lists are collected and passed along but not yet used. We may use them eventually for better error reporting. Fixes #59958. For #59338. Change-Id: I26db47ef3546e64553da49d62b23cd3ef9e2b549 Reviewed-on: https://go-review.googlesource.com/c/go/+/494116 Reviewed-by: Robert Findley <[email protected]> Auto-Submit: Robert Griesemer <[email protected]> Reviewed-by: Robert Griesemer <[email protected]> TryBot-Result: Gopher Robot <[email protected]> Run-TryBot: Robert Griesemer <[email protected]>
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‎src/cmd/compile/internal/types2/api_test.go

+29-6
Original file line numberDiff line numberDiff line change
@@ -381,6 +381,26 @@ func TestTypesInfo(t *testing.T) {
381381
{`package u3c; type _ interface{int | string | ~bool}`, `int | string`, `int | string`},
382382
{`package u3c; type _ interface{int | string | ~bool}`, `~bool`, `~bool`},
383383
{`package u3c; type _ interface{int | string | ~float64|~bool}`, `int | string | ~float64`, `int | string | ~float64`},
384+
385+
// reverse type inference
386+
{`package r1; var _ func(int) = g; func g[P any](P) {}`, `g`, `func(int)`},
387+
{`package r2; var _ func(int) = g[int]; func g[P any](P) {}`, `g`, `func[P any](P)`}, // go.dev/issues/60212
388+
{`package r3; var _ func(int) = g[int]; func g[P any](P) {}`, `g[int]`, `func(int)`},
389+
{`package r4; var _ func(int, string) = g; func g[P, Q any](P, Q) {}`, `g`, `func(int, string)`},
390+
{`package r5; var _ func(int, string) = g[int]; func g[P, Q any](P, Q) {}`, `g`, `func[P, Q any](P, Q)`}, // go.dev/issues/60212
391+
{`package r6; var _ func(int, string) = g[int]; func g[P, Q any](P, Q) {}`, `g[int]`, `func(int, string)`},
392+
393+
{`package s1; func _() { f(g) }; func f(func(int)) {}; func g[P any](P) {}`, `g`, `func(int)`},
394+
{`package s2; func _() { f(g[int]) }; func f(func(int)) {}; func g[P any](P) {}`, `g`, `func[P any](P)`}, // go.dev/issues/60212
395+
{`package s3; func _() { f(g[int]) }; func f(func(int)) {}; func g[P any](P) {}`, `g[int]`, `func(int)`},
396+
{`package s4; func _() { f(g) }; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}`, `g`, `func(int, string)`},
397+
{`package s5; func _() { f(g[int]) }; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}`, `g`, `func[P, Q any](P, Q)`}, // go.dev/issues/60212
398+
{`package s6; func _() { f(g[int]) }; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}`, `g[int]`, `func(int, string)`},
399+
400+
{`package s7; func _() { f(g, h) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `g`, `func(int, int)`},
401+
{`package s8; func _() { f(g, h) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `h`, `func(int, string)`},
402+
{`package s9; func _() { f(g, h[int]) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `h`, `func[P, Q any](P, Q)`}, // go.dev/issues/60212
403+
{`package s10; func _() { f(g, h[int]) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `h[int]`, `func(int, string)`},
384404
}
385405

386406
for _, test := range tests {
@@ -414,7 +434,7 @@ func TestTypesInfo(t *testing.T) {
414434

415435
// check that type is correct
416436
if got := typ.String(); got != test.typ {
417-
t.Errorf("package %s: got %s; want %s", name, got, test.typ)
437+
t.Errorf("package %s: expr = %s: got %s; want %s", name, test.expr, got, test.typ)
418438
}
419439
}
420440
}
@@ -551,18 +571,21 @@ type T[P any] []P
551571
[]testInst{{`foo`, []string{`int`}, `func(int)`}},
552572
},
553573

554-
// reverse type parameter inference
574+
// reverse type inference
555575
{`package reverse1a; var f func(int) = g; func g[P any](P) {}`,
556576
[]testInst{{`g`, []string{`int`}, `func(int)`}},
557577
},
558578
{`package reverse1b; func f(func(int)) {}; func g[P any](P) {}; func _() { f(g) }`,
559579
[]testInst{{`g`, []string{`int`}, `func(int)`}},
560580
},
561-
{`package reverse2a; var f func(int) string = g; func g[P, Q any](P) Q { var q Q; return q }`,
562-
[]testInst{{`g`, []string{`int`, `string`}, `func(int) string`}},
581+
{`package reverse2a; var f func(int, string) = g; func g[P, Q any](P, Q) {}`,
582+
[]testInst{{`g`, []string{`int`, `string`}, `func(int, string)`}},
583+
},
584+
{`package reverse2b; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}; func _() { f(g) }`,
585+
[]testInst{{`g`, []string{`int`, `string`}, `func(int, string)`}},
563586
},
564-
{`package reverse2b; func f(func(int) string) {}; func g[P, Q any](P) Q { var q Q; return q }; func _() { f(g) }`,
565-
[]testInst{{`g`, []string{`int`, `string`}, `func(int) string`}},
587+
{`package reverse2c; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}; func _() { f(g[int]) }`,
588+
[]testInst{{`g`, []string{`int`, `string`}, `func(int, string)`}},
566589
},
567590
// reverse3a not possible (cannot assign to generic function outside of argument passing)
568591
{`package reverse3b; func f[R any](func(int) R) {}; func g[P any](P) string { return "" }; func _() { f(g) }`,

‎src/cmd/compile/internal/types2/builtins.go

+1-1
Original file line numberDiff line numberDiff line change
@@ -143,7 +143,7 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
143143
arg(&x, i)
144144
alist2 = append(alist2, &x)
145145
}
146-
check.arguments(call, sig, nil, nil, alist2) // discard result (we know the result type)
146+
check.arguments(call, sig, nil, nil, alist2, nil, nil) // discard result (we know the result type)
147147
// ok to continue even if check.arguments reported errors
148148

149149
x.mode = value

‎src/cmd/compile/internal/types2/call.go

+118-44
Original file line numberDiff line numberDiff line change
@@ -321,8 +321,8 @@ func (check *Checker) callExpr(x *operand, call *syntax.CallExpr) exprKind {
321321
}
322322

323323
// evaluate arguments
324-
args := check.genericExprList(call.ArgList)
325-
sig = check.arguments(call, sig, targs, xlist, args)
324+
args, atargs, atxlist := check.genericExprList(call.ArgList)
325+
sig = check.arguments(call, sig, targs, xlist, args, atargs, atxlist)
326326

327327
if wasGeneric && sig.TypeParams().Len() == 0 {
328328
// update the recorded type of call.Fun to its instantiated type
@@ -358,65 +358,123 @@ func (check *Checker) callExpr(x *operand, call *syntax.CallExpr) exprKind {
358358

359359
// exprList evaluates a list of expressions and returns the corresponding operands.
360360
// A single-element expression list may evaluate to multiple operands.
361-
func (check *Checker) exprList(elist []syntax.Expr) []*operand {
362-
switch len(elist) {
363-
case 0:
364-
return nil
365-
366-
case 1:
367-
xlist, _ := check.multiExpr(elist[0], false)
368-
return xlist
369-
370-
default:
361+
func (check *Checker) exprList(elist []syntax.Expr) (xlist []*operand) {
362+
if n := len(elist); n == 1 {
363+
xlist, _ = check.multiExpr(elist[0], false)
364+
} else if n > 1 {
371365
// multiple (possibly invalid) values
372-
xlist := make([]*operand, len(elist))
366+
xlist = make([]*operand, n)
373367
for i, e := range elist {
374368
var x operand
375369
check.expr(nil, &x, e)
376370
xlist[i] = &x
377371
}
378-
return xlist
379372
}
373+
return
380374
}
381375

382-
// genericExprList is like exprList but result operands may be generic (not fully instantiated).
383-
func (check *Checker) genericExprList(elist []syntax.Expr) []*operand {
384-
switch len(elist) {
385-
case 0:
386-
return nil
376+
// genericExprList is like exprList but result operands may be uninstantiated or partially
377+
// instantiated generic functions.
378+
// For each non-generic or uninstantiated generic operand, the corresponding targsList and
379+
// xlistList elements do not exist (targsList and xlistList are nil) or the elements are nil.
380+
// For each partially instantiated generic function operand, the corresponding targsList and
381+
// xlistList elements are the operand's partial type arguments and type expression lists.
382+
func (check *Checker) genericExprList(elist []syntax.Expr) (resList []*operand, targsList [][]Type, xlistList [][]syntax.Expr) {
383+
if debug {
384+
defer func() {
385+
// targsList and xlistList must have matching lengths
386+
assert(len(targsList) == len(xlistList))
387+
// type arguments must only exist for partially instantiated functions
388+
for i, x := range resList {
389+
if i < len(targsList) {
390+
if n := len(targsList[i]); n > 0 {
391+
// x must be a partially instantiated function
392+
assert(n < x.typ.(*Signature).TypeParams().Len())
393+
}
394+
}
395+
}
396+
}()
397+
}
387398

388-
case 1:
399+
if n := len(elist); n == 1 {
400+
// single value (possibly a partially instantiated function), or a multi-valued expression
389401
e := elist[0]
390402
var x operand
391-
check.rawExpr(nil, &x, e, nil, true)
392-
check.exclude(&x, 1<<novalue|1<<builtin|1<<typexpr)
393-
394-
if t, ok := x.typ.(*Tuple); ok && x.mode != invalid {
395-
// multiple values - cannot be generic
396-
xlist := make([]*operand, t.Len())
397-
for i, v := range t.vars {
398-
xlist[i] = &operand{mode: value, expr: e, typ: v.typ}
403+
if inst, _ := e.(*syntax.IndexExpr); inst != nil && check.indexExpr(&x, inst) {
404+
// x is a generic function.
405+
targs, xlist := check.funcInst(nil, x.Pos(), &x, inst, false)
406+
if targs != nil {
407+
// x was not instantiated: collect the (partial) type arguments.
408+
targsList = [][]Type{targs}
409+
xlistList = [][]syntax.Expr{xlist}
410+
// Update x.expr so that we can record the partially instantiated function.
411+
x.expr = inst
412+
} else {
413+
// x was instantiated: we must record it here because we didn't
414+
// use the usual expression evaluators.
415+
check.record(&x)
416+
}
417+
resList = []*operand{&x}
418+
} else {
419+
// x is not a function instantiation (it may still be a generic function).
420+
check.rawExpr(nil, &x, e, nil, true)
421+
check.exclude(&x, 1<<novalue|1<<builtin|1<<typexpr)
422+
if t, ok := x.typ.(*Tuple); ok && x.mode != invalid {
423+
// x is a function call returning multiple values; it cannot be generic.
424+
resList = make([]*operand, t.Len())
425+
for i, v := range t.vars {
426+
resList[i] = &operand{mode: value, expr: e, typ: v.typ}
427+
}
428+
} else {
429+
// x is exactly one value (possibly invalid or uninstantiated generic function).
430+
resList = []*operand{&x}
399431
}
400-
return xlist
401432
}
402-
403-
// exactly one (possible invalid or generic) value
404-
return []*operand{&x}
405-
406-
default:
407-
// multiple (possibly invalid) values
408-
xlist := make([]*operand, len(elist))
433+
} else if n > 1 {
434+
// multiple values
435+
resList = make([]*operand, n)
436+
targsList = make([][]Type, n)
437+
xlistList = make([][]syntax.Expr, n)
409438
for i, e := range elist {
410439
var x operand
411-
check.genericExpr(&x, e)
412-
xlist[i] = &x
440+
if inst, _ := e.(*syntax.IndexExpr); inst != nil && check.indexExpr(&x, inst) {
441+
// x is a generic function.
442+
targs, xlist := check.funcInst(nil, x.Pos(), &x, inst, false)
443+
if targs != nil {
444+
// x was not instantiated: collect the (partial) type arguments.
445+
targsList[i] = targs
446+
xlistList[i] = xlist
447+
// Update x.expr so that we can record the partially instantiated function.
448+
x.expr = inst
449+
} else {
450+
// x was instantiated: we must record it here because we didn't
451+
// use the usual expression evaluators.
452+
check.record(&x)
453+
}
454+
} else {
455+
// x is exactly one value (possibly invalid or uninstantiated generic function).
456+
check.genericExpr(&x, e)
457+
}
458+
resList[i] = &x
413459
}
414-
return xlist
415460
}
461+
462+
return
416463
}
417464

418-
// xlist is the list of type argument expressions supplied in the source code.
419-
func (check *Checker) arguments(call *syntax.CallExpr, sig *Signature, targs []Type, xlist []syntax.Expr, args []*operand) (rsig *Signature) {
465+
// arguments type-checks arguments passed to a function call with the given signature.
466+
// The function and its arguments may be generic, and possibly partially instantiated.
467+
// targs and xlist are the function's type arguments (and corresponding expressions).
468+
// args are the function arguments. If an argument args[i] is a partially instantiated
469+
// generic function, atargs[i] and atxlist[i] are the corresponding type arguments
470+
// (and corresponding expressions).
471+
// If the callee is variadic, arguments adjusts its signature to match the provided
472+
// arguments. The type parameters and arguments of the callee and all its arguments
473+
// are used together to infer any missing type arguments, and the callee and argument
474+
// functions are instantiated as necessary.
475+
// The result signature is the (possibly adjusted and instantiated) function signature.
476+
// If an error occured, the result signature is the incoming sig.
477+
func (check *Checker) arguments(call *syntax.CallExpr, sig *Signature, targs []Type, xlist []syntax.Expr, args []*operand, atargs [][]Type, atxlist [][]syntax.Expr) (rsig *Signature) {
420478
rsig = sig
421479

422480
// Function call argument/parameter count requirements
@@ -516,7 +574,12 @@ func (check *Checker) arguments(call *syntax.CallExpr, sig *Signature, targs []T
516574
var tmp Type
517575
tparams, tmp = check.renameTParams(call.Pos(), sig.TypeParams().list(), sigParams)
518576
sigParams = tmp.(*Tuple)
577+
// make sure targs and tparams have the same length
578+
for len(targs) < len(tparams) {
579+
targs = append(targs, nil)
580+
}
519581
}
582+
assert(len(tparams) == len(targs))
520583

521584
// collect type parameters from generic function arguments
522585
var genericArgs []int // indices of generic function arguments
@@ -533,10 +596,20 @@ func (check *Checker) arguments(call *syntax.CallExpr, sig *Signature, targs []T
533596
asig.tparams = &TypeParamList{atparams} // renameTParams doesn't touch associated type parameters
534597
arg.typ = asig // new type identity for the function argument
535598
tparams = append(tparams, atparams...)
599+
// add partial list of type arguments, if any
600+
if i < len(atargs) {
601+
targs = append(targs, atargs[i]...)
602+
}
603+
// make sure targs and tparams have the same length
604+
for len(targs) < len(tparams) {
605+
targs = append(targs, nil)
606+
}
536607
genericArgs = append(genericArgs, i)
537608
}
538609
}
539610
}
611+
assert(len(tparams) == len(targs))
612+
540613
// at the moment we only support implicit instantiations of argument functions
541614
_ = len(genericArgs) > 0 && check.verifyVersionf(check.pkg, args[genericArgs[0]], go1_21, "implicitly instantiated function as argument")
542615

@@ -574,11 +647,12 @@ func (check *Checker) arguments(call *syntax.CallExpr, sig *Signature, targs []T
574647
// compute argument signatures: instantiate if needed
575648
j := n
576649
for _, i := range genericArgs {
577-
asig := args[i].typ.(*Signature)
650+
arg := args[i]
651+
asig := arg.typ.(*Signature)
578652
k := j + asig.TypeParams().Len()
579653
// targs[j:k] are the inferred type arguments for asig
580-
asig = check.instantiateSignature(call.Pos(), args[i].expr, asig, targs[j:k], nil) // TODO(gri) provide xlist if possible (partial instantiations)
581-
args[i].typ = asig
654+
arg.typ = check.instantiateSignature(call.Pos(), arg.expr, asig, targs[j:k], nil) // TODO(gri) provide xlist if possible (partial instantiations)
655+
check.record(arg) // record here because we didn't use the usual expr evaluators
582656
j = k
583657
}
584658
}

‎src/go/types/api_test.go

+29-6
Original file line numberDiff line numberDiff line change
@@ -381,6 +381,26 @@ func TestTypesInfo(t *testing.T) {
381381
{`package u3c; type _ interface{int | string | ~bool}`, `int | string`, `int | string`},
382382
{`package u3c; type _ interface{int | string | ~bool}`, `~bool`, `~bool`},
383383
{`package u3c; type _ interface{int | string | ~float64|~bool}`, `int | string | ~float64`, `int | string | ~float64`},
384+
385+
// reverse type inference
386+
{`package r1; var _ func(int) = g; func g[P any](P) {}`, `g`, `func(int)`},
387+
{`package r2; var _ func(int) = g[int]; func g[P any](P) {}`, `g`, `func[P any](P)`}, // go.dev/issues/60212
388+
{`package r3; var _ func(int) = g[int]; func g[P any](P) {}`, `g[int]`, `func(int)`},
389+
{`package r4; var _ func(int, string) = g; func g[P, Q any](P, Q) {}`, `g`, `func(int, string)`},
390+
{`package r5; var _ func(int, string) = g[int]; func g[P, Q any](P, Q) {}`, `g`, `func[P, Q any](P, Q)`}, // go.dev/issues/60212
391+
{`package r6; var _ func(int, string) = g[int]; func g[P, Q any](P, Q) {}`, `g[int]`, `func(int, string)`},
392+
393+
{`package s1; func _() { f(g) }; func f(func(int)) {}; func g[P any](P) {}`, `g`, `func(int)`},
394+
{`package s2; func _() { f(g[int]) }; func f(func(int)) {}; func g[P any](P) {}`, `g`, `func[P any](P)`}, // go.dev/issues/60212
395+
{`package s3; func _() { f(g[int]) }; func f(func(int)) {}; func g[P any](P) {}`, `g[int]`, `func(int)`},
396+
{`package s4; func _() { f(g) }; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}`, `g`, `func(int, string)`},
397+
{`package s5; func _() { f(g[int]) }; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}`, `g`, `func[P, Q any](P, Q)`}, // go.dev/issues/60212
398+
{`package s6; func _() { f(g[int]) }; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}`, `g[int]`, `func(int, string)`},
399+
400+
{`package s7; func _() { f(g, h) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `g`, `func(int, int)`},
401+
{`package s8; func _() { f(g, h) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `h`, `func(int, string)`},
402+
{`package s9; func _() { f(g, h[int]) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `h`, `func[P, Q any](P, Q)`}, // go.dev/issues/60212
403+
{`package s10; func _() { f(g, h[int]) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `h[int]`, `func(int, string)`},
384404
}
385405

386406
for _, test := range tests {
@@ -414,7 +434,7 @@ func TestTypesInfo(t *testing.T) {
414434

415435
// check that type is correct
416436
if got := typ.String(); got != test.typ {
417-
t.Errorf("package %s: got %s; want %s", name, got, test.typ)
437+
t.Errorf("package %s: expr = %s: got %s; want %s", name, test.expr, got, test.typ)
418438
}
419439
}
420440
}
@@ -551,18 +571,21 @@ type T[P any] []P
551571
[]testInst{{`foo`, []string{`int`}, `func(int)`}},
552572
},
553573

554-
// reverse type parameter inference
574+
// reverse type inference
555575
{`package reverse1a; var f func(int) = g; func g[P any](P) {}`,
556576
[]testInst{{`g`, []string{`int`}, `func(int)`}},
557577
},
558578
{`package reverse1b; func f(func(int)) {}; func g[P any](P) {}; func _() { f(g) }`,
559579
[]testInst{{`g`, []string{`int`}, `func(int)`}},
560580
},
561-
{`package reverse2a; var f func(int) string = g; func g[P, Q any](P) Q { var q Q; return q }`,
562-
[]testInst{{`g`, []string{`int`, `string`}, `func(int) string`}},
581+
{`package reverse2a; var f func(int, string) = g; func g[P, Q any](P, Q) {}`,
582+
[]testInst{{`g`, []string{`int`, `string`}, `func(int, string)`}},
583+
},
584+
{`package reverse2b; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}; func _() { f(g) }`,
585+
[]testInst{{`g`, []string{`int`, `string`}, `func(int, string)`}},
563586
},
564-
{`package reverse2b; func f(func(int) string) {}; func g[P, Q any](P) Q { var q Q; return q }; func _() { f(g) }`,
565-
[]testInst{{`g`, []string{`int`, `string`}, `func(int) string`}},
587+
{`package reverse2c; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}; func _() { f(g[int]) }`,
588+
[]testInst{{`g`, []string{`int`, `string`}, `func(int, string)`}},
566589
},
567590
// reverse3a not possible (cannot assign to generic function outside of argument passing)
568591
{`package reverse3b; func f[R any](func(int) R) {}; func g[P any](P) string { return "" }; func _() { f(g) }`,

‎src/go/types/builtins.go

+1-1
Original file line numberDiff line numberDiff line change
@@ -144,7 +144,7 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
144144
arg(&x, i)
145145
alist2 = append(alist2, &x)
146146
}
147-
check.arguments(call, sig, nil, nil, alist2) // discard result (we know the result type)
147+
check.arguments(call, sig, nil, nil, alist2, nil, nil) // discard result (we know the result type)
148148
// ok to continue even if check.arguments reported errors
149149

150150
x.mode = value

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