unpack.go

     1  // Copyright 2023 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 astutil
     6  
     7  import (
     8  	"go/ast"
     9  
    10  	"golang.org/x/tools/internal/typeparams"
    11  )
    12  
    13  // UnpackRecv unpacks a receiver type expression, reporting whether it is a
    14  // pointer receiver, along with the type name identifier and any receiver type
    15  // parameter identifiers.
    16  //
    17  // Copied (with modifications) from go/types.
    18  func UnpackRecv(rtyp ast.Expr) (ptr bool, rname *ast.Ident, tparams []*ast.Ident) {
    19  L: // unpack receiver type
    20  	// This accepts invalid receivers such as ***T and does not
    21  	// work for other invalid receivers, but we don't care. The
    22  	// validity of receiver expressions is checked elsewhere.
    23  	for {
    24  		switch t := rtyp.(type) {
    25  		case *ast.ParenExpr:
    26  			rtyp = t.X
    27  		case *ast.StarExpr:
    28  			ptr = true
    29  			rtyp = t.X
    30  		default:
    31  			break L
    32  		}
    33  	}
    34  
    35  	// unpack type parameters, if any
    36  	switch rtyp.(type) {
    37  	case *ast.IndexExpr, *ast.IndexListExpr:
    38  		var indices []ast.Expr
    39  		rtyp, _, indices, _ = typeparams.UnpackIndexExpr(rtyp)
    40  		for _, arg := range indices {
    41  			var par *ast.Ident
    42  			switch arg := arg.(type) {
    43  			case *ast.Ident:
    44  				par = arg
    45  			default:
    46  				// ignore errors
    47  			}
    48  			if par == nil {
    49  				par = &ast.Ident{NamePos: arg.Pos(), Name: "_"}
    50  			}
    51  			tparams = append(tparams, par)
    52  		}
    53  	}
    54  
    55  	// unpack receiver name
    56  	if name, _ := rtyp.(*ast.Ident); name != nil {
    57  		rname = name
    58  	}
    59  
    60  	return
    61  }
    62
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