Initialize module and dependencies

vendor/golang.org/x/vuln/internal/vulncheck/slicing.go

@@ -0,0 +1,46 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package vulncheck
+
+import (
+	"golang.org/x/tools/go/callgraph"
+	"golang.org/x/tools/go/ssa"
+)
+
+// forwardSlice computes the transitive closure of functions forward reachable
+// via calls in cg or referred to in an instruction starting from `sources`.
+func forwardSlice(sources map[*ssa.Function]bool, cg *callgraph.Graph) map[*ssa.Function]bool {
+	seen := make(map[*ssa.Function]bool)
+	var visit func(f *ssa.Function)
+	visit = func(f *ssa.Function) {
+		if seen[f] {
+			return
+		}
+		seen[f] = true
+
+		if n := cg.Nodes[f]; n != nil {
+			for _, e := range n.Out {
+				if e.Site != nil {
+					visit(e.Callee.Func)
+				}
+			}
+		}
+
+		var buf [10]*ssa.Value // avoid alloc in common case
+		for _, b := range f.Blocks {
+			for _, instr := range b.Instrs {
+				for _, op := range instr.Operands(buf[:0]) {
+					if fn, ok := (*op).(*ssa.Function); ok {
+						visit(fn)
+					}
+				}
+			}
+		}
+	}
+	for source := range sources {
+		visit(source)
+	}
+	return seen
+}