diff options
| author | Dmitry Vyukov <dvyukov@google.com> | 2020-07-04 11:12:55 +0200 |
|---|---|---|
| committer | Dmitry Vyukov <dvyukov@google.com> | 2020-07-04 15:05:30 +0200 |
| commit | c7d7f10bdff703e4a3c0414e8a33d4e45c91eb35 (patch) | |
| tree | 0dff0ee1f98dbfa3ad8776112053a450d176592b /vendor/github.com/go-toolsmith/astcast/README.md | |
| parent | 9573094ce235bd9afe88f5da27a47dd6bcc1e13b (diff) | |
go.mod: vendor golangci-lint
Diffstat (limited to 'vendor/github.com/go-toolsmith/astcast/README.md')
| -rw-r--r-- | vendor/github.com/go-toolsmith/astcast/README.md | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/vendor/github.com/go-toolsmith/astcast/README.md b/vendor/github.com/go-toolsmith/astcast/README.md new file mode 100644 index 000000000..b618da461 --- /dev/null +++ b/vendor/github.com/go-toolsmith/astcast/README.md @@ -0,0 +1,86 @@ +[](https://goreportcard.com/report/github.com/go-toolsmith/astcast) +[](https://godoc.org/github.com/go-toolsmith/astcast) + +# astcast + +Package astcast wraps type assertion operations in such way that you don't have +to worry about nil pointer results anymore. + +## Installation + +```bash +go get -v github.com/go-toolsmith/astcast +``` + +## Example + +```go +package main + +import ( + "fmt" + + "github.com/go-toolsmith/astcast" + "github.com/go-toolsmith/strparse" +) + +func main() { + x := strparse.Expr(`(foo * bar) + 1`) + + // x type is ast.Expr, we want to access bar operand + // that is a RHS of the LHS of the addition. + // Note that addition LHS (X field) is has parenthesis, + // so we have to remove them too. + + add := astcast.ToBinaryExpr(x) + mul := astcast.ToBinaryExpr(astcast.ToParenExpr(add.X).X) + bar := astcast.ToIdent(mul.Y) + fmt.Printf("%T %s\n", bar, bar.Name) // => *ast.Ident bar + + // If argument has different dynamic type, + // non-nil sentinel object of requested type is returned. + // Those sentinel objects are exported so if you need + // to know whether it was a nil interface value of + // failed type assertion, you can compare returned + // object with such a sentinel. + + y := astcast.ToCallExpr(strparse.Expr(`x`)) + if y == astcast.NilCallExpr { + fmt.Println("it is a sentinel, type assertion failed") + } +} +``` + +Without `astcast`, you would have to do a lots of type assertions: + +```go +package main + +import ( + "fmt" + + "github.com/go-toolsmith/strparse" +) + +func main() { + x := strparse.Expr(`(foo * bar) + 1`) + + add, ok := x.(*ast.BinaryExpr) + if !ok || add == nil { + return + } + additionLHS, ok := add.X.(*ast.ParenExpr) + if !ok || additionLHS == nil { + return + } + mul, ok := additionLHS.X.(*ast.BinaryExpr) + if !ok || mul == nil { + return + } + bar, ok := mul.Y.(*ast.Ident) + if !ok || bar == nil { + return + } + fmt.Printf("%T %s\n", bar, bar.Name) +} +``` |
