src/cmd/compile/internal/types2/context.go     | 7 ++++---
 src/cmd/compile/internal/types2/instantiate.go | 3 ++-
 src/go/types/context.go                        | 7 ++++---
 src/go/types/instantiate.go                    | 3 ++-

diff --git a/src/cmd/compile/internal/types2/context.go b/src/cmd/compile/internal/types2/context.go
index 7abea6b654b34dd738a707c21c3cd11a3ee48669..2d790fe5dddbbf30aa025241daeadfb3a7c2c595 100644
--- a/src/cmd/compile/internal/types2/context.go
+++ b/src/cmd/compile/internal/types2/context.go
@@ -12,11 +12,12 @@ 	"strings"
 	"sync"
 )
 
-// An Context is an opaque type checking context. It may be used to share
+// A Context is an opaque type checking context. It may be used to share
 // identical type instances across type-checked packages or calls to
-// Instantiate.
+// Instantiate. Contexts are safe for concurrent use.
 //
-// It is safe for concurrent use.
+// The use of a shared context does not guarantee that identical instances are
+// deduplicated in all cases.
 type Context struct {
 	mu        sync.Mutex
 	typeMap   map[string][]ctxtEntry // type hash -> instances entries
diff --git a/src/cmd/compile/internal/types2/instantiate.go b/src/cmd/compile/internal/types2/instantiate.go
index 9eced489dcf114a190838f93258faa1c7a8cd707..2dc82d852e0fa794d4e40fc620d7b8a29ed1b6b9 100644
--- a/src/cmd/compile/internal/types2/instantiate.go
+++ b/src/cmd/compile/internal/types2/instantiate.go
@@ -24,7 +24,8 @@ // If ctxt is non-nil, it may be used to de-duplicate the instance against
 // previous instances with the same identity. As a special case, generic
 // *Signature origin types are only considered identical if they are pointer
 // equivalent, so that instantiating distinct (but possibly identical)
-// signatures will yield different instances.
+// signatures will yield different instances. The use of a shared context does
+// not guarantee that identical instances are deduplicated in all cases.
 //
 // If validate is set, Instantiate verifies that the number of type arguments
 // and parameters match, and that the type arguments satisfy their
diff --git a/src/go/types/context.go b/src/go/types/context.go
index ff4bf89f3cb0076abca2a199c2288bee980276a9..692b3a66828a9c593432c1a8a4ad92fc9be0f626 100644
--- a/src/go/types/context.go
+++ b/src/go/types/context.go
@@ -12,11 +12,12 @@ 	"strings"
 	"sync"
 )
 
-// An Context is an opaque type checking context. It may be used to share
+// A Context is an opaque type checking context. It may be used to share
 // identical type instances across type-checked packages or calls to
-// Instantiate.
+// Instantiate. Contexts are safe for concurrent use.
 //
-// It is safe for concurrent use.
+// The use of a shared context does not guarantee that identical instances are
+// deduplicated in all cases.
 type Context struct {
 	mu        sync.Mutex
 	typeMap   map[string][]ctxtEntry // type hash -> instances entries
diff --git a/src/go/types/instantiate.go b/src/go/types/instantiate.go
index a48174665739f8206504b17a8e93024c708be83e..8813217eca2ff1361c95c5492e38000a05d1d56e 100644
--- a/src/go/types/instantiate.go
+++ b/src/go/types/instantiate.go
@@ -24,7 +24,8 @@ // If ctxt is non-nil, it may be used to de-duplicate the instance against
 // previous instances with the same identity. As a special case, generic
 // *Signature origin types are only considered identical if they are pointer
 // equivalent, so that instantiating distinct (but possibly identical)
-// signatures will yield different instances.
+// signatures will yield different instances. The use of a shared context does
+// not guarantee that identical instances are deduplicated in all cases.
 //
 // If validate is set, Instantiate verifies that the number of type arguments
 // and parameters match, and that the type arguments satisfy their