mirror of
https://github.com/golang/go
synced 2024-11-18 23:34:45 -07:00
f895b43688
This removes much of the AST logic out of main.go, and makes it easier to build custom vet binaries The trade-off in this change is for flexibility. There's very little change in the per-check files, a lot less code in main.go (specifically the AST walking logic has shrunk), and it makes it much easier to build custom vet binaries simply by dropping new source files in the directory. LGTM=josharian, r R=r, josharian, kamil.kisiel CC=golang-codereviews https://golang.org/cl/83400043
69 lines
1.4 KiB
Go
69 lines
1.4 KiB
Go
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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/*
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This file contains the code to check for useless function comparisons.
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A useless comparison is one like f == nil as opposed to f() == nil.
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*/
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package main
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import (
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"go/ast"
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"go/token"
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"code.google.com/p/go.tools/go/types"
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)
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func init() {
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register("nilfunc",
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"check for comparisons between functions and nil",
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checkNilFuncComparison,
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binaryExpr)
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}
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func checkNilFuncComparison(f *File, node ast.Node) {
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e := node.(*ast.BinaryExpr)
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// Only want == or != comparisons.
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if e.Op != token.EQL && e.Op != token.NEQ {
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return
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}
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// Only want comparisons with a nil identifier on one side.
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var e2 ast.Expr
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switch {
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case f.isNil(e.X):
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e2 = e.Y
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case f.isNil(e.Y):
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e2 = e.X
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default:
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return
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}
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// Only want identifiers or selector expressions.
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var obj types.Object
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switch v := e2.(type) {
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case *ast.Ident:
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obj = f.pkg.uses[v]
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case *ast.SelectorExpr:
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obj = f.pkg.uses[v.Sel]
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default:
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return
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}
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// Only want functions.
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if _, ok := obj.(*types.Func); !ok {
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return
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}
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f.Badf(e.Pos(), "comparison of function %v %v nil is always %v", obj.Name(), e.Op, e.Op == token.NEQ)
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}
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// isNil reports whether the provided expression is the built-in nil
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// identifier.
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func (f *File) isNil(e ast.Expr) bool {
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return f.pkg.types[e].Type == types.Typ[types.UntypedNil]
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}
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