add bugs section in readme for type parameter switch statements

README.md

@@ -15,6 +15,12 @@ The package provides an `Analyzer` that follows the guidelines in the
 [`go/analysis`][3] package; this should make it possible to integrate
 exhaustive with your own analysis driver program.
 
+## Bugs
+
+`exhaustive` does not report missing cases if the switch statement
+switches on a type parameterized type. See [this
+issue](https://github.com/nishanths/exhaustive/issues/31) for details.
+
 ## Example
 
 Given the enum

testdata/xxx/typeparam/main.go

@@ -0,0 +1,32 @@
+package typeparam
+
+// Testing instructions:
+//  $ go build ./cmd/exhaustive
+//  $ ./exhaustive ./testdata/xxx/typeparam
+
+type M int
+
+const (
+	A M = iota
+	B
+)
+
+type N uint
+
+const (
+	C N = iota
+	D
+)
+
+func foo[T M](v T) {
+	switch v {
+	case T(A):
+	}
+}
+
+func bar[T M | N](v T) {
+	switch v {
+	case T(A):
+	case T(D):
+	}
+}