diff --git a/src/cmd/vet/copylock.go b/src/cmd/vet/copylock.go
index e8f94fc685..31c1257a47 100644
--- a/src/cmd/vet/copylock.go
+++ b/src/cmd/vet/copylock.go
@@ -61,10 +61,7 @@ func checkCopyLocksGenDecl(f *File, gd *ast.GenDecl) {
 		return
 	}
 	for _, spec := range gd.Specs {
-		valueSpec, ok := spec.(*ast.ValueSpec)
-		if !ok {
-			continue
-		}
+		valueSpec := spec.(*ast.ValueSpec)
 		for i, x := range valueSpec.Values {
 			if path := lockPathRhs(f, x); path != nil {
 				f.Badf(x.Pos(), "variable declaration copies lock value to %v: %v", valueSpec.Names[i].Name, path)
diff --git a/src/cmd/vet/shadow.go b/src/cmd/vet/shadow.go
index 764129d94c..29c952fd88 100644
--- a/src/cmd/vet/shadow.go
+++ b/src/cmd/vet/shadow.go
@@ -188,7 +188,8 @@ func checkShadowDecl(f *File, d *ast.GenDecl) {
 	for _, spec := range d.Specs {
 		valueSpec, ok := spec.(*ast.ValueSpec)
 		if !ok {
-			continue
+			f.Badf(spec.Pos(), "invalid AST: var GenDecl not ValueSpec")
+			return
 		}
 		// Don't complain about deliberate redeclarations of the form
 		//	var i = i
diff --git a/src/cmd/vet/testdata/copylock.go b/src/cmd/vet/testdata/copylock.go
index 52ac29c47c..35ed766f1d 100644
--- a/src/cmd/vet/testdata/copylock.go
+++ b/src/cmd/vet/testdata/copylock.go
@@ -1,7 +1,6 @@
 package testdata
 
 import (
-	"runtime"
 	"sync"
 	"sync/atomic"
 )
@@ -157,11 +156,3 @@ func AtomicTypesCheck() {
 	vP := &vX
 	vZ := &atomic.Value{}
 }
-
-// ensure we don't crash when we encounter aliases; issue 17755
-
-var _ => runtime.MemProfileRate
-
-const _ => runtime.Compiler
-
-type _ => sync.Mutex