go/types: avoid infinite expansion for invalid recursive generic types
This is a clean port of CL 355732 from types2 to go/types.
Fixes #48951.
Change-Id: I9f8cc0655166835d9450608f6e50b726659a73f1
Reviewed-on: https://go-review.googlesource.com/c/go/+/355733
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
diff --git a/src/go/types/decl.go b/src/go/types/decl.go
index f97fa25..4aa49b1 100644
--- a/src/go/types/decl.go
+++ b/src/go/types/decl.go
@@ -329,7 +329,17 @@
}
case *Named:
- t.resolve(check.conf.Context)
+ // If t is parameterized, we should be considering the instantiated (expanded)
+ // form of t, but in general we can't with this algorithm: if t is an invalid
+ // type it may be so because it infinitely expands through a type parameter.
+ // Instantiating such a type would lead to an infinite sequence of instantiations.
+ // In general, we need "type flow analysis" to recognize those cases.
+ // Example: type A[T any] struct{ x A[*T] } (issue #48951)
+ // In this algorithm we always only consider the orginal, uninstantiated type.
+ // This won't recognize some invalid cases with parameterized types, but it
+ // will terminate.
+ t = t.orig
+
// don't touch the type if it is from a different package or the Universe scope
// (doing so would lead to a race condition - was issue #35049)
if t.obj.pkg != check.pkg {
@@ -357,7 +367,7 @@
check.cycleError(path[i:])
t.info = invalid
t.underlying = Typ[Invalid]
- return t.info
+ return invalid
}
}
panic("cycle start not found")
diff --git a/src/go/types/testdata/check/issues.go2 b/src/go/types/testdata/check/issues.go2
index a994d73..c46a34e 100644
--- a/src/go/types/testdata/check/issues.go2
+++ b/src/go/types/testdata/check/issues.go2
@@ -146,8 +146,8 @@
}
// Infinite generic type declarations must lead to an error.
-type inf1[T any] struct{ _ inf1 /* ERROR illegal cycle */ [T] }
-type inf2[T any] struct{ inf2 /* ERROR illegal cycle */ [T] }
+type inf1 /* ERROR illegal cycle */ [T any] struct{ _ inf1[T] }
+type inf2 /* ERROR illegal cycle */ [T any] struct{ inf2[T] }
// The implementation of conversions T(x) between integers and floating-point
// numbers checks that both T and x have either integer or floating-point
diff --git a/src/go/types/testdata/fixedbugs/issue39634.go2 b/src/go/types/testdata/fixedbugs/issue39634.go2
index c46d38f..5cff6e7 100644
--- a/src/go/types/testdata/fixedbugs/issue39634.go2
+++ b/src/go/types/testdata/fixedbugs/issue39634.go2
@@ -37,8 +37,8 @@
// func main8() {}
// crash 9
-type foo9[A any] interface { foo9 /* ERROR illegal cycle */ [A] }
-func _() { var _ = new(foo9 /* ERROR illegal cycle */ [int]) }
+type foo9 /* ERROR illegal cycle */ [A any] interface { foo9[A] }
+func _() { var _ = new(foo9[int]) }
// crash 12
var u /* ERROR cycle */ , i [func /* ERROR used as value */ /* ERROR used as value */ (u, c /* ERROR undeclared */ /* ERROR undeclared */ ) {}(0, len /* ERROR must be called */ /* ERROR must be called */ )]c /* ERROR undeclared */ /* ERROR undeclared */
diff --git a/src/go/types/testdata/fixedbugs/issue39938.go2 b/src/go/types/testdata/fixedbugs/issue39938.go2
index 0da6e10..31bec5f 100644
--- a/src/go/types/testdata/fixedbugs/issue39938.go2
+++ b/src/go/types/testdata/fixedbugs/issue39938.go2
@@ -3,6 +3,8 @@
// license that can be found in the LICENSE file.
// Check "infinite expansion" cycle errors across instantiated types.
+// We can't detect these errors anymore at the moment. See #48962 for
+// details.
package p
@@ -11,11 +13,11 @@
type E2[P any] struct{ _ P }
type E3[P any] struct{ _ *P }
-type T0 /* ERROR illegal cycle */ struct {
+type T0 /* illegal cycle */ struct {
_ E0[T0]
}
-type T0_ /* ERROR illegal cycle */ struct {
+type T0_ /* illegal cycle */ struct {
E0[T0_]
}
@@ -23,7 +25,7 @@
_ E1[T1]
}
-type T2 /* ERROR illegal cycle */ struct {
+type T2 /* illegal cycle */ struct {
_ E2[T2]
}
@@ -33,7 +35,7 @@
// some more complex cases
-type T4 /* ERROR illegal cycle */ struct {
+type T4 /* illegal cycle */ struct {
_ E0[E2[T4]]
}
@@ -41,7 +43,7 @@
_ E0[E2[E0[E1[E2[[10]T5]]]]]
}
-type T6 /* ERROR illegal cycle */ struct {
+type T6 /* illegal cycle */ struct {
_ E0[[10]E2[E0[E2[E2[T6]]]]]
}
diff --git a/src/go/types/testdata/fixedbugs/issue48951.go2 b/src/go/types/testdata/fixedbugs/issue48951.go2
new file mode 100644
index 0000000..cf02cc1
--- /dev/null
+++ b/src/go/types/testdata/fixedbugs/issue48951.go2
@@ -0,0 +1,21 @@
+// Copyright 2020 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
+
+type (
+ A1 /* ERROR illegal cycle */ [P any] [10]A1[P]
+ A2 /* ERROR illegal cycle */ [P any] [10]A2[*P]
+ A3[P any] [10]*A3[P]
+
+ L1[P any] []L1[P]
+
+ S1 /* ERROR illegal cycle */ [P any] struct{ f S1[P] }
+ S2 /* ERROR illegal cycle */ [P any] struct{ f S2[*P] } // like example in issue
+ S3[P any] struct{ f *S3[P] }
+
+ I1 /* ERROR illegal cycle */ [P any] interface{ I1[P] }
+ I2 /* ERROR illegal cycle */ [P any] interface{ I2[*P] }
+ I3[P any] interface{ *I3 /* ERROR interface contains type constraints */ [P] }
+)
