example_test.go

Documentation: go/token

		 1  // Copyright 2018 The Go Authors. All rights reserved.
		 2  // Use of this source code is governed by a BSD-style
		 3  // license that can be found in the LICENSE file.
		 4  
		 5  package token_test
		 6  
		 7  import (
		 8  	"fmt"
		 9  	"go/ast"
		10  	"go/parser"
		11  	"go/token"
		12  )
		13  
		14  func Example_retrievePositionInfo() {
		15  	fset := token.NewFileSet()
		16  
		17  	const src = `package main
		18  
		19  import "fmt"
		20  
		21  import "go/token"
		22  
		23  //line :1:5
		24  type p = token.Pos
		25  
		26  const bad = token.NoPos
		27  
		28  //line fake.go:42:11
		29  func ok(pos p) bool {
		30  	return pos != bad
		31  }
		32  
		33  /*line :7:9*/func main() {
		34  	fmt.Println(ok(bad) == bad.IsValid())
		35  }
		36  `
		37  
		38  	f, err := parser.ParseFile(fset, "main.go", src, 0)
		39  	if err != nil {
		40  		fmt.Println(err)
		41  		return
		42  	}
		43  
		44  	// Print the location and kind of each declaration in f.
		45  	for _, decl := range f.Decls {
		46  		// Get the filename, line, and column back via the file set.
		47  		// We get both the relative and absolute position.
		48  		// The relative position is relative to the last line directive.
		49  		// The absolute position is the exact position in the source.
		50  		pos := decl.Pos()
		51  		relPosition := fset.Position(pos)
		52  		absPosition := fset.PositionFor(pos, false)
		53  
		54  		// Either a FuncDecl or GenDecl, since we exit on error.
		55  		kind := "func"
		56  		if gen, ok := decl.(*ast.GenDecl); ok {
		57  			kind = gen.Tok.String()
		58  		}
		59  
		60  		// If the relative and absolute positions differ, show both.
		61  		fmtPosition := relPosition.String()
		62  		if relPosition != absPosition {
		63  			fmtPosition += "[" + absPosition.String() + "]"
		64  		}
		65  
		66  		fmt.Printf("%s: %s\n", fmtPosition, kind)
		67  	}
		68  
		69  	//Output:
		70  	//
		71  	// main.go:3:1: import
		72  	// main.go:5:1: import
		73  	// main.go:1:5[main.go:8:1]: type
		74  	// main.go:3:1[main.go:10:1]: const
		75  	// fake.go:42:11[main.go:13:1]: func
		76  	// fake.go:7:9[main.go:17:14]: func
		77  }
		78
View as plain text