go/src/cmd/compile/internal/types2/labels.go

// labels checks correct label use in body.
func (check *Checker) labels(body *syntax.BlockStmt) { … }

type block …

// insert records a new label declaration for the current block.
// The label must not have been declared before in any block.
func (b *block) insert(s *syntax.LabeledStmt) { … }

// gotoTarget returns the labeled statement in the current
// or an enclosing block with the given label name, or nil.
func (b *block) gotoTarget(name string) *syntax.LabeledStmt { … }

// enclosingTarget returns the innermost enclosing labeled
// statement with the given label name, or nil.
func (b *block) enclosingTarget(name string) *syntax.LabeledStmt { … }

// blockBranches processes a block's statement list and returns the set of outgoing forward jumps.
// all is the scope of all declared labels, parent the set of labels declared in the immediately
// enclosing block, and lstmt is the labeled statement this block is associated with (or nil).
func (check *Checker) blockBranches(all *Scope, parent *block, lstmt *syntax.LabeledStmt, list []syntax.Stmt) []*syntax.BranchStmt { … }