lsp/source: create zero value ast.Exprs
In support of https://golang.org/cl/224960, add utility functions that
create zero value expressions for a given types.Type. There are probably
some bugs here but they pass the basic tests in that CL.
Known problems: it skips through type aliases, and can't handle
anonymous structs/interfaces. Hopefully it's pretty unusual to return
those.
Change-Id: I69a388d9ce9bd60bc230e4a3d2b30f581ec25698
Reviewed-on: https://go-review.googlesource.com/c/tools/+/225177
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rohan Challa <rohan@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
diff --git a/internal/lsp/source/util.go b/internal/lsp/source/util.go
index 09f3569..407169c 100644
--- a/internal/lsp/source/util.go
+++ b/internal/lsp/source/util.go
@@ -16,6 +16,7 @@
"sort"
"strings"
+ "golang.org/x/tools/go/ast/astutil"
"golang.org/x/tools/internal/lsp/protocol"
"golang.org/x/tools/internal/span"
errors "golang.org/x/xerrors"
@@ -774,3 +775,81 @@
return types.TypeString(T, qf) + "{}"
}
}
+
+func zeroValue(fset *token.FileSet, f *ast.File, pkg *types.Package, typ types.Type) ast.Expr {
+ under := typ
+ if n, ok := typ.(*types.Named); ok {
+ under = n.Underlying()
+ }
+ switch u := under.(type) {
+ case *types.Basic:
+ switch {
+ case u.Info()&types.IsNumeric != 0:
+ return &ast.BasicLit{Kind: token.INT, Value: "0"}
+ case u.Info()&types.IsBoolean != 0:
+ return &ast.Ident{Name: "false"}
+ case u.Info()&types.IsString != 0:
+ return &ast.BasicLit{Kind: token.STRING, Value: `""`}
+ default:
+ panic("unknown basic type")
+ }
+ case *types.Chan, *types.Interface, *types.Map, *types.Pointer, *types.Signature, *types.Slice:
+ return ast.NewIdent("nil")
+ case *types.Struct:
+ texpr := typeExpr(fset, f, pkg, typ) // typ because we want the name here.
+ if texpr == nil {
+ return nil
+ }
+ return &ast.CompositeLit{
+ Type: texpr,
+ }
+ case *types.Array:
+ texpr := typeExpr(fset, f, pkg, u.Elem())
+ if texpr == nil {
+ return nil
+ }
+ return &ast.CompositeLit{
+ Type: &ast.ArrayType{
+ Elt: texpr,
+ Len: &ast.BasicLit{Kind: token.INT, Value: fmt.Sprintf("%v", u.Len())},
+ },
+ }
+ }
+ return nil
+}
+
+func typeExpr(fset *token.FileSet, f *ast.File, pkg *types.Package, typ types.Type) ast.Expr {
+ switch t := typ.(type) {
+ case *types.Basic:
+ switch t.Kind() {
+ case types.UnsafePointer:
+ return &ast.SelectorExpr{X: ast.NewIdent("unsafe"), Sel: ast.NewIdent("Pointer")}
+ default:
+ return ast.NewIdent(t.Name())
+ }
+ case *types.Named:
+ if t.Obj().Pkg() == pkg {
+ return ast.NewIdent(t.Obj().Name())
+ }
+ pkgName := t.Obj().Pkg().Name()
+ // If the file already imports the package under another name, use that.
+ for _, group := range astutil.Imports(fset, f) {
+ for _, cand := range group {
+ if strings.Trim(cand.Path.Value, `"`) == t.Obj().Pkg().Path() {
+ if cand.Name != nil && cand.Name.Name != "" {
+ pkgName = cand.Name.Name
+ }
+ }
+ }
+ }
+ if pkgName == "." {
+ return ast.NewIdent(t.Obj().Name())
+ }
+ return &ast.SelectorExpr{
+ X: ast.NewIdent(pkgName),
+ Sel: ast.NewIdent(t.Obj().Name()),
+ }
+ default:
+ return nil // TODO: anonymous structs, but who does that
+ }
+}
