github.com/goplusjs/gopherjs@v1.2.6-0.20211206034512-f187917453b8/compiler/analysis/escape.go (about)

     1  package analysis
     2  
     3  import (
     4  	"go/ast"
     5  	"go/token"
     6  	"go/types"
     7  )
     8  
     9  func EscapingObjects(n ast.Node, info *types.Info) []*types.Var {
    10  	v := escapeAnalysis{
    11  		info:         info,
    12  		escaping:     make(map[*types.Var]bool),
    13  		topScope:     info.Scopes[n],
    14  		bottomScopes: make(map[*types.Scope]bool),
    15  	}
    16  	ast.Walk(&v, n)
    17  	var list []*types.Var
    18  	for obj := range v.escaping {
    19  		list = append(list, obj)
    20  	}
    21  	return list
    22  }
    23  
    24  type escapeAnalysis struct {
    25  	info         *types.Info
    26  	escaping     map[*types.Var]bool
    27  	topScope     *types.Scope
    28  	bottomScopes map[*types.Scope]bool
    29  }
    30  
    31  func (v *escapeAnalysis) Visit(node ast.Node) (w ast.Visitor) {
    32  	// huge overapproximation
    33  	switch n := node.(type) {
    34  	case *ast.UnaryExpr:
    35  		if n.Op == token.AND {
    36  			if _, ok := n.X.(*ast.Ident); ok {
    37  				return &escapingObjectCollector{v}
    38  			}
    39  		}
    40  	case *ast.FuncLit:
    41  		v.bottomScopes[v.info.Scopes[n.Type]] = true
    42  		return &escapingObjectCollector{v}
    43  	case *ast.ForStmt:
    44  		v.bottomScopes[v.info.Scopes[n.Body]] = true
    45  	case *ast.RangeStmt:
    46  		v.bottomScopes[v.info.Scopes[n.Body]] = true
    47  	}
    48  	return v
    49  }
    50  
    51  type escapingObjectCollector struct {
    52  	analysis *escapeAnalysis
    53  }
    54  
    55  func (v *escapingObjectCollector) Visit(node ast.Node) (w ast.Visitor) {
    56  	if id, ok := node.(*ast.Ident); ok {
    57  		if obj, ok := v.analysis.info.Uses[id].(*types.Var); ok {
    58  			for s := obj.Parent(); s != nil; s = s.Parent() {
    59  				if s == v.analysis.topScope {
    60  					v.analysis.escaping[obj] = true
    61  					break
    62  				}
    63  				if v.analysis.bottomScopes[s] {
    64  					break
    65  				}
    66  			}
    67  		}
    68  	}
    69  	return v
    70  }