github.com/jd-ly/tools@v0.5.7/go/ssa/util.go (about)

     1  // Copyright 2013 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 ssa
     6  
     7  // This file defines a number of miscellaneous utility functions.
     8  
     9  import (
    10  	"fmt"
    11  	"go/ast"
    12  	"go/token"
    13  	"go/types"
    14  	"io"
    15  	"os"
    16  
    17  	"github.com/jd-ly/tools/go/ast/astutil"
    18  )
    19  
    20  //// AST utilities
    21  
    22  func unparen(e ast.Expr) ast.Expr { return astutil.Unparen(e) }
    23  
    24  // isBlankIdent returns true iff e is an Ident with name "_".
    25  // They have no associated types.Object, and thus no type.
    26  //
    27  func isBlankIdent(e ast.Expr) bool {
    28  	id, ok := e.(*ast.Ident)
    29  	return ok && id.Name == "_"
    30  }
    31  
    32  //// Type utilities.  Some of these belong in go/types.
    33  
    34  // isPointer returns true for types whose underlying type is a pointer.
    35  func isPointer(typ types.Type) bool {
    36  	_, ok := typ.Underlying().(*types.Pointer)
    37  	return ok
    38  }
    39  
    40  func isInterface(T types.Type) bool { return types.IsInterface(T) }
    41  
    42  // deref returns a pointer's element type; otherwise it returns typ.
    43  func deref(typ types.Type) types.Type {
    44  	if p, ok := typ.Underlying().(*types.Pointer); ok {
    45  		return p.Elem()
    46  	}
    47  	return typ
    48  }
    49  
    50  // recvType returns the receiver type of method obj.
    51  func recvType(obj *types.Func) types.Type {
    52  	return obj.Type().(*types.Signature).Recv().Type()
    53  }
    54  
    55  // logStack prints the formatted "start" message to stderr and
    56  // returns a closure that prints the corresponding "end" message.
    57  // Call using 'defer logStack(...)()' to show builder stack on panic.
    58  // Don't forget trailing parens!
    59  //
    60  func logStack(format string, args ...interface{}) func() {
    61  	msg := fmt.Sprintf(format, args...)
    62  	io.WriteString(os.Stderr, msg)
    63  	io.WriteString(os.Stderr, "\n")
    64  	return func() {
    65  		io.WriteString(os.Stderr, msg)
    66  		io.WriteString(os.Stderr, " end\n")
    67  	}
    68  }
    69  
    70  // newVar creates a 'var' for use in a types.Tuple.
    71  func newVar(name string, typ types.Type) *types.Var {
    72  	return types.NewParam(token.NoPos, nil, name, typ)
    73  }
    74  
    75  // anonVar creates an anonymous 'var' for use in a types.Tuple.
    76  func anonVar(typ types.Type) *types.Var {
    77  	return newVar("", typ)
    78  }
    79  
    80  var lenResults = types.NewTuple(anonVar(tInt))
    81  
    82  // makeLen returns the len builtin specialized to type func(T)int.
    83  func makeLen(T types.Type) *Builtin {
    84  	lenParams := types.NewTuple(anonVar(T))
    85  	return &Builtin{
    86  		name: "len",
    87  		sig:  types.NewSignature(nil, lenParams, lenResults, false),
    88  	}
    89  }