Update and fix staticcheck

vendor/honnef.co/go/tools/functions/stub.go

@@ -0,0 +1,32 @@
+package functions
+
+import (
+	"honnef.co/go/tools/ir"
+)
+
+// IsStub reports whether a function is a stub. A function is
+// considered a stub if it has no instructions or if all it does is
+// return a constant value.
+func IsStub(fn *ir.Function) bool {
+	for _, b := range fn.Blocks {
+		for _, instr := range b.Instrs {
+			switch instr.(type) {
+			case *ir.Const:
+				// const naturally has no side-effects
+			case *ir.Panic:
+				// panic is a stub if it only uses constants
+			case *ir.Return:
+				// return is a stub if it only uses constants
+			case *ir.DebugRef:
+			case *ir.Jump:
+				// if there are no disallowed instructions, then we're
+				// only jumping to the exit block (or possibly
+				// somewhere else that's stubby?)
+			default:
+				// all other instructions are assumed to do actual work
+				return false
+			}
+		}
+	}
+	return true
+}