diff --git a/src/cmd/compile/internal/types2/infer.go b/src/cmd/compile/internal/types2/infer.go
index ed11ae8e4c..ee2bcf79e4 100644
--- a/src/cmd/compile/internal/types2/infer.go
+++ b/src/cmd/compile/internal/types2/infer.go
@@ -694,17 +694,13 @@ func (w *cycleFinder) varList(list []*Var) {
 	}
 }
 
-// If tpar is a type parameter in list, tparamIndex returns the type parameter index.
-// Otherwise, the result is < 0. tpar must not be nil.
+// If tpar is a type parameter in list, tparamIndex returns the index
+// of the type parameter in list. Otherwise the result is < 0.
 func tparamIndex(list []*TypeParam, tpar *TypeParam) int {
-	// Once a type parameter is bound its index is >= 0. However, there are some
-	// code paths (namely tracing and type hashing) by which it is possible to
-	// arrive here with a type parameter that has not been bound, hence the check
-	// for 0 <= i below.
-	// TODO(rfindley): investigate a better approach for guarding against using
-	// unbound type parameters.
-	if i := tpar.index; 0 <= i && i < len(list) && list[i] == tpar {
-		return i
+	for i, p := range list {
+		if p == tpar {
+			return i
+		}
 	}
 	return -1
 }
diff --git a/src/go/types/infer.go b/src/go/types/infer.go
index c2138f4a36..0f8e7aeddc 100644
--- a/src/go/types/infer.go
+++ b/src/go/types/infer.go
@@ -696,17 +696,13 @@ func (w *cycleFinder) varList(list []*Var) {
 	}
 }
 
-// If tpar is a type parameter in list, tparamIndex returns the type parameter index.
-// Otherwise, the result is < 0. tpar must not be nil.
+// If tpar is a type parameter in list, tparamIndex returns the index
+// of the type parameter in list. Otherwise the result is < 0.
 func tparamIndex(list []*TypeParam, tpar *TypeParam) int {
-	// Once a type parameter is bound its index is >= 0. However, there are some
-	// code paths (namely tracing and type hashing) by which it is possible to
-	// arrive here with a type parameter that has not been bound, hence the check
-	// for 0 <= i below.
-	// TODO(rfindley): investigate a better approach for guarding against using
-	// unbound type parameters.
-	if i := tpar.index; 0 <= i && i < len(list) && list[i] == tpar {
-		return i
+	for i, p := range list {
+		if p == tpar {
+			return i
+		}
 	}
 	return -1
 }