don't hoist local closure variables to parent function

Signed-off-by: Achille Roussel <[email protected]>

compiler/compile.go

@@ -337,7 +337,7 @@ func (c *compiler) compileFunction(p *packages.Package, fn *ast.FuncDecl, color
 	// declarations to the function prologue. We downgrade inline var decls and
 	// assignments that use := to assignments that use =. Constant decls are
 	// hoisted and also have their value assigned in the function prologue.
-	decls := extractDecls(fn, p.TypesInfo)
+	decls := extractDecls(fn.Body, p.TypesInfo)
 	renameObjects(fn, p.TypesInfo, decls)
 	for _, decl := range decls {
 		gen.Body.List = append(gen.Body.List, &ast.DeclStmt{Decl: decl})

compiler/decls.go

@@ -21,9 +21,13 @@ import (
 // Note that declarations are extracted from all nested scopes within the
 // function body, so there may be duplicate identifiers. Identifiers can be
 // disambiguated using (*types.Info).ObjectOf(ident).
-func extractDecls(fn *ast.FuncDecl, info *types.Info) (decls []*ast.GenDecl) {
-	ast.Inspect(fn.Body, func(node ast.Node) bool {
+func extractDecls(tree ast.Node, info *types.Info) (decls []*ast.GenDecl) {
+	ast.Inspect(tree, func(node ast.Node) bool {
 		switch n := node.(type) {
+		case *ast.FuncLit:
+			// Stop when we encounter a function listeral so we don't hoist its
+			// local variables into the scope of its parent function.
+			return false
 		case *ast.GenDecl: // const, var, type
 			if n.Tok == token.TYPE || n.Tok == token.CONST {
 				decls = append(decls, n)
@@ -135,6 +139,8 @@ func renameObjects(tree ast.Node, info *types.Info, decls []*ast.GenDecl) {
 func removeDecls(tree ast.Node) {
 	astutil.Apply(tree, func(cursor *astutil.Cursor) bool {
 		switch n := cursor.Node().(type) {
+		case *ast.FuncLit:
+			return false
 		case *ast.AssignStmt:
 			if n.Tok == token.DEFINE {
 				if _, ok := cursor.Parent().(*ast.TypeSwitchStmt); ok {