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gofmt: simplify "x, _ = range y" to "x = range y"

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(inspired by CL 3529041 by hitchmanr@gmail.com)

R=rsc
CC=golang-dev
https://golang.org/cl/3527042
This commit is contained in:
Robert Griesemer 2010-12-09 10:11:57 -08:00
parent 2bdb2e78fe
commit e2da3b6498
1 changed files with 18 additions and 8 deletions
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26
src/cmd/gofmt/simplify.go
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@ -10,11 +10,13 @@ import (
) )
type compositeLitFinder struct{} type simplifier struct{}
func (f *compositeLitFinder) Visit(node interface{}) ast.Visitor { func (s *simplifier) Visit(node interface{}) ast.Visitor {
if outer, ok := node.(*ast.CompositeLit); ok { switch n := node.(type) {
case *ast.CompositeLit:
// array, slice, and map composite literals may be simplified // array, slice, and map composite literals may be simplified
outer := n
var eltType ast.Expr var eltType ast.Expr
switch typ := outer.Type.(type) { switch typ := outer.Type.(type) {
case *ast.ArrayType: case *ast.ArrayType:
@ -41,17 +43,25 @@ func (f *compositeLitFinder) Visit(node interface{}) ast.Visitor {
} }
} }
// node was simplified - stop walk // node was simplified - stop walk (there are no subnodes to simplify)
return nil return nil
} }
case *ast.RangeStmt:
// range of the form: for x, _ = range v {...}
// can be simplified to: for x = range v {...}
if n.Value != nil {
if ident, ok := n.Value.(*ast.Ident); ok && ident.Name == "_" {
n.Value = nil
}
}
} }
// not a composite literal or not simplified - continue walk return s
return f
} }
func simplify(node interface{}) { func simplify(node interface{}) {
var f compositeLitFinder var s simplifier
ast.Walk(&f, node) ast.Walk(&s, node)
} }