go/types, types2: keep inferring type arguments from constraints for -lang < go1.21

Fixes #60346.

Change-Id: I14834858d53fd80f8261ec0c8d0eccdd75a1bc2b
Reviewed-on: https://go-review.googlesource.com/c/go/+/496917
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

diff --git a/src/cmd/compile/internal/types2/call.go b/src/cmd/compile/internal/types2/call.go
index 301dc634770cef05525ede319f02484484abc3d6..bc3634b6bb5b26e4bb5788cf3094d11c12b2b17c 100644 (file)
--- a/src/cmd/compile/internal/types2/call.go
+++ b/src/cmd/compile/internal/types2/call.go
@@ -374,7 +374,8 @@ func (check *Checker) exprList(elist []syntax.Expr) (xlist []*operand) {
 }
 
 // genericExprList is like exprList but result operands may be uninstantiated or partially
-// instantiated generic functions.
+// 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
@@ -396,13 +397,21 @@ func (check *Checker) genericExprList(elist []syntax.Expr) (resList []*operand,
                }()
        }
 
-       if n := len(elist); n == 1 {
+       // 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, false)
+                       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}
@@ -439,7 +448,7 @@ func (check *Checker) genericExprList(elist []syntax.Expr) (resList []*operand,
                        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, false)
+                               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

diff --git a/src/go/types/call.go b/src/go/types/call.go
index c8360dce57076f60d20344771bb11d936daffb86..df48bf19e4faec8eadfc6ec9e1cc260862ece346 100644 (file)
--- a/src/go/types/call.go
+++ b/src/go/types/call.go
@@ -379,7 +379,8 @@ func (check *Checker) exprList(elist []ast.Expr) (xlist []*operand) {
 }
 
 // genericExprList is like exprList but result operands may be uninstantiated or partially
-// instantiated generic functions.
+// 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
@@ -401,13 +402,21 @@ func (check *Checker) genericExprList(elist []ast.Expr) (resList []*operand, tar
                }()
        }
 
-       if n := len(elist); n == 1 {
+       // 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 ix := typeparams.UnpackIndexExpr(e); ix != nil && check.indexExpr(&x, ix) {
                        // x is a generic function.
-                       targs, xlist := check.funcInst(nil, x.Pos(), &x, ix, false)
+                       targs, xlist := check.funcInst(nil, x.Pos(), &x, ix, infer)
                        if targs != nil {
                                // x was not instantiated: collect the (partial) type arguments.
                                targsList = [][]Type{targs}
@@ -444,7 +453,7 @@ func (check *Checker) genericExprList(elist []ast.Expr) (resList []*operand, tar
                        var x operand
                        if ix := typeparams.UnpackIndexExpr(e); ix != nil && check.indexExpr(&x, ix) {
                                // x is a generic function.
-                               targs, xlist := check.funcInst(nil, x.Pos(), &x, ix, false)
+                               targs, xlist := check.funcInst(nil, x.Pos(), &x, ix, infer)
                                if targs != nil {
                                        // x was not instantiated: collect the (partial) type arguments.
                                        targsList[i] = targs

diff --git a/src/internal/types/testdata/fixedbugs/issue60346.go b/src/internal/types/testdata/fixedbugs/issue60346.go
new file mode 100644 (file)
index 0000000..6dc057b
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue60346.go
@@ -0,0 +1,17 @@
+// -lang=go1.20
+
+// Copyright 2023 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 p
+
+func F[P any, Q *P](p P) {}
+
+var _ = F[int]
+
+func G[R any](func(R)) {}
+
+func _() {
+       G(F[int])
+}