diff --git a/src/go/types/NOTES b/src/go/types/NOTES
index 389d10d2f7..87bbbec6e9 100644
--- a/src/go/types/NOTES
+++ b/src/go/types/NOTES
@@ -11,7 +11,6 @@ TODO
 - use []*TypeParam for tparams in subst? (unclear)
 - should we use nil instead of &emptyInterface for no type bounds (as an optimization)?
 - TBD: in prose, should we use "generic" or "parameterized" (try to be consistent)
-- don't apply receiver type identifier substitution in place (typexpr.go)
 
 ----------------------------------------------------------------------------------------------------
 KNOWN ISSUES
diff --git a/src/go/types/expr.go b/src/go/types/expr.go
index 1261f06dfb..46b899be71 100644
--- a/src/go/types/expr.go
+++ b/src/go/types/expr.go
@@ -1522,9 +1522,14 @@ func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
 		if x.mode == invalid {
 			goto Error
 		}
-		xtyp, _ := x.typ.Underlying().(*Interface)
-		if xtyp == nil {
-			check.invalidOp(x.pos(), "%s is not an interface", x)
+		var xtyp *Interface
+		switch t := x.typ.Underlying().(type) {
+		case *Interface:
+			xtyp = t
+		case *TypeParam:
+			xtyp = t.Interface()
+		default:
+			check.invalidOp(x.pos(), "%s is not an interface or generic type", x)
 			goto Error
 		}
 		// x.(type) expressions are handled explicitly in type switches
diff --git a/src/go/types/stmt.go b/src/go/types/stmt.go
index ad86bd5a82..fb4e9ed741 100644
--- a/src/go/types/stmt.go
+++ b/src/go/types/stmt.go
@@ -599,7 +599,7 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 			return
 		}
 
-		// rhs must be of the form: expr.(type) and expr must be an interface
+		// rhs must be of the form: expr.(type) and expr must be an interface or generic type
 		expr, _ := rhs.(*ast.TypeAssertExpr)
 		if expr == nil || expr.Type != nil {
 			check.invalidAST(s.Pos(), "incorrect form of type switch guard")
@@ -610,9 +610,14 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 		if x.mode == invalid {
 			return
 		}
-		xtyp, _ := x.typ.Underlying().(*Interface)
-		if xtyp == nil {
-			check.errorf(x.pos(), "%s is not an interface", &x)
+		var xtyp *Interface
+		switch t := x.typ.Underlying().(type) {
+		case *Interface:
+			xtyp = t
+		case *TypeParam:
+			xtyp = t.Interface()
+		default:
+			check.errorf(x.pos(), "%s is not an interface or generic type", &x)
 			return
 		}
 
diff --git a/src/go/types/testdata/todos.go2 b/src/go/types/testdata/todos.go2
index 675385a51d..7d200c4de5 100644
--- a/src/go/types/testdata/todos.go2
+++ b/src/go/types/testdata/todos.go2
@@ -32,12 +32,6 @@ func _(type T interface{ type *int })(p T) {
 	_ = *p /* ERROR cannot indirect */
 }
 
-// type assertions over generic types are not yet supported
-func _(type T interface{ type int })(x T) {
-	_ = T /* ERROR not an expression */ .(int)
-	_ = x /* ERROR not an interface */ .(int)
-}
-
 // calling of a generic variable is not yet supported
 func _(type T interface{ type func() })(f T) {
 	f /* ERROR cannot call */ ()
diff --git a/src/go/types/testdata/typeparams.go2 b/src/go/types/testdata/typeparams.go2
index 970db54674..e2ed36d6f8 100644
--- a/src/go/types/testdata/typeparams.go2
+++ b/src/go/types/testdata/typeparams.go2
@@ -4,6 +4,8 @@
 
 package p
 
+import "io" // for type assertion tests
+
 func identity(type T)(x T) T { return x }
 
 func _(type)(x int) int
@@ -314,4 +316,27 @@ var _ I2(int, float32) = R2(int, float32){}
 type R2(type P, Q) struct{}
 
 func (_ R2(X, Y)) m1(X)
-func (_ R2(X, Y)) m2(X) Y
\ No newline at end of file
+func (_ R2(X, Y)) m2(X) Y
+
+// type assertions and type switches over generic types
+
+// ReadByte1 corresponds to the ReadByte example in the contracts draft design.
+func ReadByte1(type T io.Reader)(r T) (byte, error) {
+	if br, ok := r.(io.ByteReader); ok {
+		return br.ReadByte()
+	}
+	var b [1]byte
+	_, err := r.Read(b[:])
+	return b[0], err
+}
+
+// ReadBytes2 is like ReadByte1 but uses a type switch instead.
+func ReadByte2(type T io.Reader)(r T) (byte, error) {
+        switch br := r.(type) {
+        case io.ByteReader:
+                return br.ReadByte()
+        }
+	var b [1]byte
+	_, err := r.Read(b[:])
+	return b[0], err
+}