quirks.go

     1  // Copyright 2021 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 noder
     6  
     7  import (
     8  	"fmt"
     9  
    10  	"cmd/compile/internal/syntax"
    11  )
    12  
    13  // typeExprEndPos returns the position that noder would leave base.Pos
    14  // after parsing the given type expression.
    15  //
    16  // Deprecated: This function exists to emulate position semantics from
    17  // Go 1.17, necessary for compatibility with the backend DWARF
    18  // generation logic that assigns variables to their appropriate scope.
    19  func typeExprEndPos(expr0 syntax.Expr) syntax.Pos {
    20  	for {
    21  		switch expr := expr0.(type) {
    22  		case *syntax.Name:
    23  			return expr.Pos()
    24  		case *syntax.SelectorExpr:
    25  			return expr.X.Pos()
    26  
    27  		case *syntax.ParenExpr:
    28  			expr0 = expr.X
    29  
    30  		case *syntax.Operation:
    31  			assert(expr.Op == syntax.Mul)
    32  			assert(expr.Y == nil)
    33  			expr0 = expr.X
    34  
    35  		case *syntax.ArrayType:
    36  			expr0 = expr.Elem
    37  		case *syntax.ChanType:
    38  			expr0 = expr.Elem
    39  		case *syntax.DotsType:
    40  			expr0 = expr.Elem
    41  		case *syntax.MapType:
    42  			expr0 = expr.Value
    43  		case *syntax.SliceType:
    44  			expr0 = expr.Elem
    45  
    46  		case *syntax.StructType:
    47  			return expr.Pos()
    48  
    49  		case *syntax.InterfaceType:
    50  			expr0 = lastFieldType(expr.MethodList)
    51  			if expr0 == nil {
    52  				return expr.Pos()
    53  			}
    54  
    55  		case *syntax.FuncType:
    56  			expr0 = lastFieldType(expr.ResultList)
    57  			if expr0 == nil {
    58  				expr0 = lastFieldType(expr.ParamList)
    59  				if expr0 == nil {
    60  					return expr.Pos()
    61  				}
    62  			}
    63  
    64  		case *syntax.IndexExpr: // explicit type instantiation
    65  			targs := syntax.UnpackListExpr(expr.Index)
    66  			expr0 = targs[len(targs)-1]
    67  
    68  		default:
    69  			panic(fmt.Sprintf("%s: unexpected type expression %v", expr.Pos(), syntax.String(expr)))
    70  		}
    71  	}
    72  }
    73  
    74  func lastFieldType(fields []*syntax.Field) syntax.Expr {
    75  	if len(fields) == 0 {
    76  		return nil
    77  	}
    78  	return fields[len(fields)-1].Type
    79  }
    80
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