package unused import ( "fmt" "go/ast" "go/token" "go/types" "io" "strings" "sync" "sync/atomic" "golang.org/x/tools/go/analysis" "honnef.co/go/tools/go/types/typeutil" "honnef.co/go/tools/internal/passes/buildssa" "honnef.co/go/tools/lint" "honnef.co/go/tools/lint/lintdsl" "honnef.co/go/tools/ssa" ) // The graph we construct omits nodes along a path that do not // contribute any new information to the solution. For example, the // full graph for a function with a receiver would be Func -> // Signature -> Var -> Type. However, since signatures cannot be // unused, and receivers are always considered used, we can compact // the graph down to Func -> Type. This makes the graph smaller, but // harder to debug. // TODO(dh): conversions between structs mark fields as used, but the // conversion itself isn't part of that subgraph. even if the function // containing the conversion is unused, the fields will be marked as // used. // TODO(dh): we cannot observe function calls in assembly files. /* - packages use: - (1.1) exported named types (unless in package main) - (1.2) exported functions (unless in package main) - (1.3) exported variables (unless in package main) - (1.4) exported constants (unless in package main) - (1.5) init functions - (1.6) functions exported to cgo - (1.7) the main function iff in the main package - (1.8) symbols linked via go:linkname - named types use: - (2.1) exported methods - (2.2) the type they're based on - (2.3) all their aliases. we can't easily track uses of aliases because go/types turns them into uses of the aliased types. assume that if a type is used, so are all of its aliases. - (2.4) the pointer type. this aids with eagerly implementing interfaces. if a method that implements an interface is defined on a pointer receiver, and the pointer type is never used, but the named type is, then we still want to mark the method as used. - variables and constants use: - their types - functions use: - (4.1) all their arguments, return parameters and receivers - (4.2) anonymous functions defined beneath them - (4.3) closures and bound methods. this implements a simplified model where a function is used merely by being referenced, even if it is never called. that way we don't have to keep track of closures escaping functions. - (4.4) functions they return. we assume that someone else will call the returned function - (4.5) functions/interface methods they call - types they instantiate or convert to - (4.7) fields they access - (4.8) types of all instructions - (4.9) package-level variables they assign to iff in tests (sinks for benchmarks) - conversions use: - (5.1) when converting between two equivalent structs, the fields in either struct use each other. the fields are relevant for the conversion, but only if the fields are also accessed outside the conversion. - (5.2) when converting to or from unsafe.Pointer, mark all fields as used. - structs use: - (6.1) fields of type NoCopy sentinel - (6.2) exported fields - (6.3) embedded fields that help implement interfaces (either fully implements it, or contributes required methods) (recursively) - (6.4) embedded fields that have exported methods (recursively) - (6.5) embedded structs that have exported fields (recursively) - (7.1) field accesses use fields - (7.2) fields use their types - (8.0) How we handle interfaces: - (8.1) We do not technically care about interfaces that only consist of exported methods. Exported methods on concrete types are always marked as used. - Any concrete type implements all known interfaces. Even if it isn't assigned to any interfaces in our code, the user may receive a value of the type and expect to pass it back to us through an interface. Concrete types use their methods that implement interfaces. If the type is used, it uses those methods. Otherwise, it doesn't. This way, types aren't incorrectly marked reachable through the edge from method to type. - (8.3) All interface methods are marked as used, even if they never get called. This is to accomodate sum types (unexported interface method that must exist but never gets called.) - (8.4) All embedded interfaces are marked as used. This is an extension of 8.3, but we have to explicitly track embedded interfaces because in a chain C->B->A, B wouldn't be marked as used by 8.3 just because it contributes A's methods to C. - Inherent uses: - thunks and other generated wrappers call the real function - (9.2) variables use their types - (9.3) types use their underlying and element types - (9.4) conversions use the type they convert to - (9.5) instructions use their operands - (9.6) instructions use their operands' types - (9.7) variable _reads_ use variables, writes do not, except in tests - (9.8) runtime functions that may be called from user code via the compiler - const groups: (10.1) if one constant out of a block of constants is used, mark all of them used. a lot of the time, unused constants exist for the sake of completeness. See also https://github.com/dominikh/go-tools/issues/365 - (11.1) anonymous struct types use all their fields. we cannot deduplicate struct types, as that leads to order-dependent reportings. we can't not deduplicate struct types while still tracking fields, because then each instance of the unnamed type in the data flow chain will get its own fields, causing false positives. Thus, we only accurately track fields of named struct types, and assume that unnamed struct types use all their fields. - Differences in whole program mode: - (e2) types aim to implement all exported interfaces from all packages - (e3) exported identifiers aren't automatically used. for fields and methods this poses extra issues due to reflection. We assume that all exported fields are used. We also maintain a list of known reflection-based method callers. */ func assert(b bool) { if !b { panic("failed assertion") } } func typString(obj types.Object) string { switch obj := obj.(type) { case *types.Func: return "func" case *types.Var: if obj.IsField() { return "field" } return "var" case *types.Const: return "const" case *types.TypeName: return "type" default: return "identifier" } } // /usr/lib/go/src/runtime/proc.go:433:6: func badmorestackg0 is unused (U1000) // Functions defined in the Go runtime that may be called through // compiler magic or via assembly. var runtimeFuncs = map[string]bool{ // The first part of the list is copied from // cmd/compile/internal/gc/builtin.go, var runtimeDecls "newobject": true, "panicindex": true, "panicslice": true, "panicdivide": true, "panicmakeslicelen": true, "throwinit": true, "panicwrap": true, "gopanic": true, "gorecover": true, "goschedguarded": true, "printbool": true, "printfloat": true, "printint": true, "printhex": true, "printuint": true, "printcomplex": true, "printstring": true, "printpointer": true, "printiface": true, "printeface": true, "printslice": true, "printnl": true, "printsp": true, "printlock": true, "printunlock": true, "concatstring2": true, "concatstring3": true, "concatstring4": true, "concatstring5": true, "concatstrings": true, "cmpstring": true, "intstring": true, "slicebytetostring": true, "slicebytetostringtmp": true, "slicerunetostring": true, "stringtoslicebyte": true, "stringtoslicerune": true, "slicecopy": true, "slicestringcopy": true, "decoderune": true, "countrunes": true, "convI2I": true, "convT16": true, "convT32": true, "convT64": true, "convTstring": true, "convTslice": true, "convT2E": true, "convT2Enoptr": true, "convT2I": true, "convT2Inoptr": true, "assertE2I": true, "assertE2I2": true, "assertI2I": true, "assertI2I2": true, "panicdottypeE": true, "panicdottypeI": true, "panicnildottype": true, "ifaceeq": true, "efaceeq": true, "fastrand": true, "makemap64": true, "makemap": true, "makemap_small": true, "mapaccess1": true, "mapaccess1_fast32": true, "mapaccess1_fast64": true, "mapaccess1_faststr": true, "mapaccess1_fat": true, "mapaccess2": true, "mapaccess2_fast32": true, "mapaccess2_fast64": true, "mapaccess2_faststr": true, "mapaccess2_fat": true, "mapassign": true, "mapassign_fast32": true, "mapassign_fast32ptr": true, "mapassign_fast64": true, "mapassign_fast64ptr": true, "mapassign_faststr": true, "mapiterinit": true, "mapdelete": true, "mapdelete_fast32": true, "mapdelete_fast64": true, "mapdelete_faststr": true, "mapiternext": true, "mapclear": true, "makechan64": true, "makechan": true, "chanrecv1": true, "chanrecv2": true, "chansend1": true, "closechan": true, "writeBarrier": true, "typedmemmove": true, "typedmemclr": true, "typedslicecopy": true, "selectnbsend": true, "selectnbrecv": true, "selectnbrecv2": true, "selectsetpc": true, "selectgo": true, "block": true, "makeslice": true, "makeslice64": true, "growslice": true, "memmove": true, "memclrNoHeapPointers": true, "memclrHasPointers": true, "memequal": true, "memequal8": true, "memequal16": true, "memequal32": true, "memequal64": true, "memequal128": true, "int64div": true, "uint64div": true, "int64mod": true, "uint64mod": true, "float64toint64": true, "float64touint64": true, "float64touint32": true, "int64tofloat64": true, "uint64tofloat64": true, "uint32tofloat64": true, "complex128div": true, "racefuncenter": true, "racefuncenterfp": true, "racefuncexit": true, "raceread": true, "racewrite": true, "racereadrange": true, "racewriterange": true, "msanread": true, "msanwrite": true, "x86HasPOPCNT": true, "x86HasSSE41": true, "arm64HasATOMICS": true, // The second part of the list is extracted from assembly code in // the standard library, with the exception of the runtime package itself "abort": true, "aeshashbody": true, "args": true, "asminit": true, "badctxt": true, "badmcall2": true, "badmcall": true, "badmorestackg0": true, "badmorestackgsignal": true, "badsignal2": true, "callbackasm1": true, "callCfunction": true, "cgocallback_gofunc": true, "cgocallbackg": true, "checkgoarm": true, "check": true, "debugCallCheck": true, "debugCallWrap": true, "emptyfunc": true, "entersyscall": true, "exit": true, "exits": true, "exitsyscall": true, "externalthreadhandler": true, "findnull": true, "goexit1": true, "gostring": true, "i386_set_ldt": true, "_initcgo": true, "init_thread_tls": true, "ldt0setup": true, "libpreinit": true, "load_g": true, "morestack": true, "mstart": true, "nacl_sysinfo": true, "nanotimeQPC": true, "nanotime": true, "newosproc0": true, "newproc": true, "newstack": true, "noted": true, "nowQPC": true, "osinit": true, "printf": true, "racecallback": true, "reflectcallmove": true, "reginit": true, "rt0_go": true, "save_g": true, "schedinit": true, "setldt": true, "settls": true, "sighandler": true, "sigprofNonGo": true, "sigtrampgo": true, "_sigtramp": true, "sigtramp": true, "stackcheck": true, "syscall_chdir": true, "syscall_chroot": true, "syscall_close": true, "syscall_dup2": true, "syscall_execve": true, "syscall_exit": true, "syscall_fcntl": true, "syscall_forkx": true, "syscall_gethostname": true, "syscall_getpid": true, "syscall_ioctl": true, "syscall_pipe": true, "syscall_rawsyscall6": true, "syscall_rawSyscall6": true, "syscall_rawsyscall": true, "syscall_RawSyscall": true, "syscall_rawsysvicall6": true, "syscall_setgid": true, "syscall_setgroups": true, "syscall_setpgid": true, "syscall_setsid": true, "syscall_setuid": true, "syscall_syscall6": true, "syscall_syscall": true, "syscall_Syscall": true, "syscall_sysvicall6": true, "syscall_wait4": true, "syscall_write": true, "traceback": true, "tstart": true, "usplitR0": true, "wbBufFlush": true, "write": true, } type pkg struct { Fset *token.FileSet Files []*ast.File Pkg *types.Package TypesInfo *types.Info TypesSizes types.Sizes SSA *ssa.Package SrcFuncs []*ssa.Function } type Checker struct { WholeProgram bool Debug io.Writer mu sync.Mutex initialPackages map[*types.Package]struct{} allPackages map[*types.Package]struct{} graph *Graph } func NewChecker(wholeProgram bool) *Checker { return &Checker{ initialPackages: map[*types.Package]struct{}{}, allPackages: map[*types.Package]struct{}{}, WholeProgram: wholeProgram, } } func (c *Checker) Analyzer() *analysis.Analyzer { name := "U1000" if c.WholeProgram { name = "U1001" } return &analysis.Analyzer{ Name: name, Doc: "Unused code", Run: c.Run, Requires: []*analysis.Analyzer{buildssa.Analyzer}, } } func (c *Checker) Run(pass *analysis.Pass) (interface{}, error) { c.mu.Lock() if c.graph == nil { c.graph = NewGraph() c.graph.wholeProgram = c.WholeProgram c.graph.fset = pass.Fset } var visit func(pkg *types.Package) visit = func(pkg *types.Package) { if _, ok := c.allPackages[pkg]; ok { return } c.allPackages[pkg] = struct{}{} for _, imp := range pkg.Imports() { visit(imp) } } visit(pass.Pkg) c.initialPackages[pass.Pkg] = struct{}{} c.mu.Unlock() ssapkg := pass.ResultOf[buildssa.Analyzer].(*buildssa.SSA) pkg := &pkg{ Fset: pass.Fset, Files: pass.Files, Pkg: pass.Pkg, TypesInfo: pass.TypesInfo, TypesSizes: pass.TypesSizes, SSA: ssapkg.Pkg, SrcFuncs: ssapkg.SrcFuncs, } c.processPkg(c.graph, pkg) return nil, nil } func (c *Checker) ProblemObject(fset *token.FileSet, obj types.Object) lint.Problem { name := obj.Name() if sig, ok := obj.Type().(*types.Signature); ok && sig.Recv() != nil { switch sig.Recv().Type().(type) { case *types.Named, *types.Pointer: typ := types.TypeString(sig.Recv().Type(), func(*types.Package) string { return "" }) if len(typ) > 0 && typ[0] == '*' { name = fmt.Sprintf("(%s).%s", typ, obj.Name()) } else if len(typ) > 0 { name = fmt.Sprintf("%s.%s", typ, obj.Name()) } } } checkName := "U1000" if c.WholeProgram { checkName = "U1001" } return lint.Problem{ Pos: lint.DisplayPosition(fset, obj.Pos()), Message: fmt.Sprintf("%s %s is unused", typString(obj), name), Check: checkName, } } func (c *Checker) Result() []types.Object { out := c.results() out2 := make([]types.Object, 0, len(out)) for _, v := range out { if _, ok := c.initialPackages[v.Pkg()]; !ok { continue } out2 = append(out2, v) } return out2 } func (c *Checker) debugf(f string, v ...interface{}) { if c.Debug != nil { fmt.Fprintf(c.Debug, f, v...) } } func (graph *Graph) quieten(node *Node) { if node.seen { return } switch obj := node.obj.(type) { case *types.Named: for i := 0; i < obj.NumMethods(); i++ { m := obj.Method(i) if node, ok := graph.nodeMaybe(m); ok { node.quiet = true } } case *types.Struct: for i := 0; i < obj.NumFields(); i++ { if node, ok := graph.nodeMaybe(obj.Field(i)); ok { node.quiet = true } } case *types.Interface: for i := 0; i < obj.NumExplicitMethods(); i++ { m := obj.ExplicitMethod(i) if node, ok := graph.nodeMaybe(m); ok { node.quiet = true } } } } func (c *Checker) results() []types.Object { if c.graph == nil { // We never analyzed any packages return nil } var out []types.Object if c.WholeProgram { var ifaces []*types.Interface var notIfaces []types.Type // implement as many interfaces as possible c.graph.seenTypes.Iterate(func(t types.Type, _ interface{}) { switch t := t.(type) { case *types.Interface: if t.NumMethods() > 0 { ifaces = append(ifaces, t) } default: if _, ok := t.Underlying().(*types.Interface); !ok { notIfaces = append(notIfaces, t) } } }) for pkg := range c.allPackages { for _, iface := range interfacesFromExportData(pkg) { if iface.NumMethods() > 0 { ifaces = append(ifaces, iface) } } } ctx := &context{ g: c.graph, seenTypes: &c.graph.seenTypes, } // (8.0) handle interfaces // (e2) types aim to implement all exported interfaces from all packages for _, t := range notIfaces { // OPT(dh): it is unfortunate that we do not have access // to a populated method set at this point. ms := types.NewMethodSet(t) for _, iface := range ifaces { if sels, ok := c.graph.implements(t, iface, ms); ok { for _, sel := range sels { c.graph.useMethod(ctx, t, sel, t, edgeImplements) } } } } } if c.Debug != nil { debugNode := func(node *Node) { if node.obj == nil { c.debugf("n%d [label=\"Root\"];\n", node.id) } else { c.debugf("n%d [label=%q];\n", node.id, fmt.Sprintf("(%T) %s", node.obj, node.obj)) } for _, e := range node.used { for i := edgeKind(1); i < 64; i++ { if e.kind.is(1 << i) { c.debugf("n%d -> n%d [label=%q];\n", node.id, e.node.id, edgeKind(1< 1 { cg := &ConstGroup{} ctx.see(cg) for _, spec := range specs { for _, name := range spec.(*ast.ValueSpec).Names { obj := pkg.TypesInfo.ObjectOf(name) // (10.1) const groups ctx.seeAndUse(obj, cg, edgeConstGroup) ctx.use(cg, obj, edgeConstGroup) } } } } case token.VAR: for _, spec := range n.Specs { v := spec.(*ast.ValueSpec) for _, name := range v.Names { T := pkg.TypesInfo.TypeOf(name) if fn != nil { ctx.seeAndUse(T, fn, edgeVarDecl) } else { // TODO(dh): we likely want to make // the type used by the variable, not // the package containing the // variable. But then we have to take // special care of blank identifiers. ctx.seeAndUse(T, nil, edgeVarDecl) } g.typ(ctx, T, nil) } } case token.TYPE: for _, spec := range n.Specs { // go/types doesn't provide a way to go from a // types.Named to the named type it was based on // (the t1 in type t2 t1). Therefore we walk the // AST and process GenDecls. // // (2.2) named types use the type they're based on v := spec.(*ast.TypeSpec) T := pkg.TypesInfo.TypeOf(v.Type) obj := pkg.TypesInfo.ObjectOf(v.Name) ctx.see(obj) ctx.see(T) ctx.use(T, obj, edgeType) g.typ(ctx, obj.Type(), nil) g.typ(ctx, T, nil) if v.Assign != 0 { aliasFor := obj.(*types.TypeName).Type() // (2.3) named types use all their aliases. we can't easily track uses of aliases if isIrrelevant(aliasFor) { // We do not track the type this is an // alias for (for example builtins), so // just mark the alias used. // // FIXME(dh): what about aliases declared inside functions? ctx.use(obj, nil, edgeAlias) } else { ctx.see(aliasFor) ctx.seeAndUse(obj, aliasFor, edgeAlias) } } } } } return true }) } for _, m := range pkg.SSA.Members { switch m := m.(type) { case *ssa.NamedConst: // nothing to do, we collect all constants from Defs case *ssa.Global: if m.Object() != nil { ctx.see(m.Object()) if g.trackExportedIdentifier(ctx, m.Object()) { // (1.3) packages use exported variables (unless in package main) ctx.use(m.Object(), nil, edgeExportedVariable) } } case *ssa.Function: mObj := owningObject(m) if mObj != nil { ctx.see(mObj) } //lint:ignore SA9003 handled implicitly if m.Name() == "init" { // (1.5) packages use init functions // // This is handled implicitly. The generated init // function has no object, thus everything in it will // be owned by the package. } // This branch catches top-level functions, not methods. if m.Object() != nil && g.trackExportedIdentifier(ctx, m.Object()) { // (1.2) packages use exported functions (unless in package main) ctx.use(mObj, nil, edgeExportedFunction) } if m.Name() == "main" && pkg.Pkg.Name() == "main" { // (1.7) packages use the main function iff in the main package ctx.use(mObj, nil, edgeMainFunction) } if pkg.Pkg.Path() == "runtime" && runtimeFuncs[m.Name()] { // (9.8) runtime functions that may be called from user code via the compiler ctx.use(mObj, nil, edgeRuntimeFunction) } if m.Syntax() != nil { doc := m.Syntax().(*ast.FuncDecl).Doc if doc != nil { for _, cmt := range doc.List { if strings.HasPrefix(cmt.Text, "//go:cgo_export_") { // (1.6) packages use functions exported to cgo ctx.use(mObj, nil, edgeCgoExported) } } } } g.function(ctx, m) case *ssa.Type: if m.Object() != nil { ctx.see(m.Object()) if g.trackExportedIdentifier(ctx, m.Object()) { // (1.1) packages use exported named types (unless in package main) ctx.use(m.Object(), nil, edgeExportedType) } } g.typ(ctx, m.Type(), nil) default: panic(fmt.Sprintf("unreachable: %T", m)) } } if !g.wholeProgram { // When not in whole program mode we reset seenTypes after each package, // which means g.seenTypes only contains types of // interest to us. In whole program mode, we're better off // processing all interfaces at once, globally, both for // performance reasons and because in whole program mode we // actually care about all interfaces, not just the subset // that has unexported methods. var ifaces []*types.Interface var notIfaces []types.Type ctx.seenTypes.Iterate(func(t types.Type, _ interface{}) { switch t := t.(type) { case *types.Interface: // OPT(dh): (8.1) we only need interfaces that have unexported methods ifaces = append(ifaces, t) default: if _, ok := t.Underlying().(*types.Interface); !ok { notIfaces = append(notIfaces, t) } } }) // (8.0) handle interfaces for _, t := range notIfaces { ms := pkg.SSA.Prog.MethodSets.MethodSet(t) for _, iface := range ifaces { if sels, ok := g.implements(t, iface, ms); ok { for _, sel := range sels { g.useMethod(ctx, t, sel, t, edgeImplements) } } } } } } func (g *Graph) useMethod(ctx *context, t types.Type, sel *types.Selection, by interface{}, kind edgeKind) { obj := sel.Obj() path := sel.Index() assert(obj != nil) if len(path) > 1 { base := lintdsl.Dereference(t).Underlying().(*types.Struct) for _, idx := range path[:len(path)-1] { next := base.Field(idx) // (6.3) structs use embedded fields that help implement interfaces ctx.see(base) ctx.seeAndUse(next, base, edgeProvidesMethod) base, _ = lintdsl.Dereference(next.Type()).Underlying().(*types.Struct) } } ctx.seeAndUse(obj, by, kind) } func owningObject(fn *ssa.Function) types.Object { if fn.Object() != nil { return fn.Object() } if fn.Parent() != nil { return owningObject(fn.Parent()) } return nil } func (g *Graph) function(ctx *context, fn *ssa.Function) { if fn.Package() != nil && fn.Package() != ctx.pkg.SSA { return } name := fn.RelString(nil) if _, ok := ctx.seenFns[name]; ok { return } ctx.seenFns[name] = struct{}{} // (4.1) functions use all their arguments, return parameters and receivers g.signature(ctx, fn.Signature, owningObject(fn)) g.instructions(ctx, fn) for _, anon := range fn.AnonFuncs { // (4.2) functions use anonymous functions defined beneath them // // This fact is expressed implicitly. Anonymous functions have // no types.Object, so their owner is the surrounding // function. g.function(ctx, anon) } } func (g *Graph) typ(ctx *context, t types.Type, parent types.Type) { if g.wholeProgram { g.mu.Lock() } if ctx.seenTypes.At(t) != nil { if g.wholeProgram { g.mu.Unlock() } return } if g.wholeProgram { g.mu.Unlock() } if t, ok := t.(*types.Named); ok && t.Obj().Pkg() != nil { if t.Obj().Pkg() != ctx.pkg.Pkg { return } } if g.wholeProgram { g.mu.Lock() } ctx.seenTypes.Set(t, struct{}{}) if g.wholeProgram { g.mu.Unlock() } if isIrrelevant(t) { return } ctx.see(t) switch t := t.(type) { case *types.Struct: for i := 0; i < t.NumFields(); i++ { ctx.see(t.Field(i)) if t.Field(i).Exported() { // (6.2) structs use exported fields ctx.use(t.Field(i), t, edgeExportedField) } else if t.Field(i).Name() == "_" { ctx.use(t.Field(i), t, edgeBlankField) } else if isNoCopyType(t.Field(i).Type()) { // (6.1) structs use fields of type NoCopy sentinel ctx.use(t.Field(i), t, edgeNoCopySentinel) } else if parent == nil { // (11.1) anonymous struct types use all their fields. ctx.use(t.Field(i), t, edgeAnonymousStruct) } if t.Field(i).Anonymous() { // (e3) exported identifiers aren't automatically used. if !g.wholeProgram { // does the embedded field contribute exported methods to the method set? T := t.Field(i).Type() if _, ok := T.Underlying().(*types.Pointer); !ok { // An embedded field is addressable, so check // the pointer type to get the full method set T = types.NewPointer(T) } ms := ctx.pkg.SSA.Prog.MethodSets.MethodSet(T) for j := 0; j < ms.Len(); j++ { if ms.At(j).Obj().Exported() { // (6.4) structs use embedded fields that have exported methods (recursively) ctx.use(t.Field(i), t, edgeExtendsExportedMethodSet) break } } } seen := map[*types.Struct]struct{}{} var hasExportedField func(t types.Type) bool hasExportedField = func(T types.Type) bool { t, ok := lintdsl.Dereference(T).Underlying().(*types.Struct) if !ok { return false } if _, ok := seen[t]; ok { return false } seen[t] = struct{}{} for i := 0; i < t.NumFields(); i++ { field := t.Field(i) if field.Exported() { return true } if field.Embedded() && hasExportedField(field.Type()) { return true } } return false } // does the embedded field contribute exported fields? if hasExportedField(t.Field(i).Type()) { // (6.5) structs use embedded structs that have exported fields (recursively) ctx.use(t.Field(i), t, edgeExtendsExportedFields) } } g.variable(ctx, t.Field(i)) } case *types.Basic: // Nothing to do case *types.Named: // (9.3) types use their underlying and element types ctx.seeAndUse(t.Underlying(), t, edgeUnderlyingType) ctx.seeAndUse(t.Obj(), t, edgeTypeName) ctx.seeAndUse(t, t.Obj(), edgeNamedType) // (2.4) named types use the pointer type if _, ok := t.Underlying().(*types.Interface); !ok && t.NumMethods() > 0 { ctx.seeAndUse(types.NewPointer(t), t, edgePointerType) } for i := 0; i < t.NumMethods(); i++ { ctx.see(t.Method(i)) // don't use trackExportedIdentifier here, we care about // all exported methods, even in package main or in tests. if t.Method(i).Exported() && !g.wholeProgram { // (2.1) named types use exported methods ctx.use(t.Method(i), t, edgeExportedMethod) } g.function(ctx, ctx.pkg.SSA.Prog.FuncValue(t.Method(i))) } g.typ(ctx, t.Underlying(), t) case *types.Slice: // (9.3) types use their underlying and element types ctx.seeAndUse(t.Elem(), t, edgeElementType) g.typ(ctx, t.Elem(), nil) case *types.Map: // (9.3) types use their underlying and element types ctx.seeAndUse(t.Elem(), t, edgeElementType) // (9.3) types use their underlying and element types ctx.seeAndUse(t.Key(), t, edgeKeyType) g.typ(ctx, t.Elem(), nil) g.typ(ctx, t.Key(), nil) case *types.Signature: g.signature(ctx, t, nil) case *types.Interface: for i := 0; i < t.NumMethods(); i++ { m := t.Method(i) // (8.3) All interface methods are marked as used ctx.seeAndUse(m, t, edgeInterfaceMethod) ctx.seeAndUse(m.Type().(*types.Signature), m, edgeSignature) g.signature(ctx, m.Type().(*types.Signature), nil) } for i := 0; i < t.NumEmbeddeds(); i++ { tt := t.EmbeddedType(i) // (8.4) All embedded interfaces are marked as used ctx.seeAndUse(tt, t, edgeEmbeddedInterface) } case *types.Array: // (9.3) types use their underlying and element types ctx.seeAndUse(t.Elem(), t, edgeElementType) g.typ(ctx, t.Elem(), nil) case *types.Pointer: // (9.3) types use their underlying and element types ctx.seeAndUse(t.Elem(), t, edgeElementType) g.typ(ctx, t.Elem(), nil) case *types.Chan: // (9.3) types use their underlying and element types ctx.seeAndUse(t.Elem(), t, edgeElementType) g.typ(ctx, t.Elem(), nil) case *types.Tuple: for i := 0; i < t.Len(); i++ { // (9.3) types use their underlying and element types ctx.seeAndUse(t.At(i).Type(), t, edgeTupleElement|edgeType) g.typ(ctx, t.At(i).Type(), nil) } default: panic(fmt.Sprintf("unreachable: %T", t)) } } func (g *Graph) variable(ctx *context, v *types.Var) { // (9.2) variables use their types ctx.seeAndUse(v.Type(), v, edgeType) g.typ(ctx, v.Type(), nil) } func (g *Graph) signature(ctx *context, sig *types.Signature, fn types.Object) { var user interface{} = fn if fn == nil { user = sig ctx.see(sig) } if sig.Recv() != nil { ctx.seeAndUse(sig.Recv().Type(), user, edgeReceiver|edgeType) g.typ(ctx, sig.Recv().Type(), nil) } for i := 0; i < sig.Params().Len(); i++ { param := sig.Params().At(i) ctx.seeAndUse(param.Type(), user, edgeFunctionArgument|edgeType) g.typ(ctx, param.Type(), nil) } for i := 0; i < sig.Results().Len(); i++ { param := sig.Results().At(i) ctx.seeAndUse(param.Type(), user, edgeFunctionResult|edgeType) g.typ(ctx, param.Type(), nil) } } func (g *Graph) instructions(ctx *context, fn *ssa.Function) { fnObj := owningObject(fn) for _, b := range fn.Blocks { for _, instr := range b.Instrs { ops := instr.Operands(nil) switch instr.(type) { case *ssa.Store: // (9.7) variable _reads_ use variables, writes do not ops = ops[1:] case *ssa.DebugRef: ops = nil } for _, arg := range ops { walkPhi(*arg, func(v ssa.Value) { switch v := v.(type) { case *ssa.Function: // (4.3) functions use closures and bound methods. // (4.5) functions use functions they call // (9.5) instructions use their operands // (4.4) functions use functions they return. we assume that someone else will call the returned function if owningObject(v) != nil { ctx.seeAndUse(owningObject(v), fnObj, edgeInstructionOperand) } g.function(ctx, v) case *ssa.Const: // (9.6) instructions use their operands' types ctx.seeAndUse(v.Type(), fnObj, edgeType) g.typ(ctx, v.Type(), nil) case *ssa.Global: if v.Object() != nil { // (9.5) instructions use their operands ctx.seeAndUse(v.Object(), fnObj, edgeInstructionOperand) } } }) } if v, ok := instr.(ssa.Value); ok { if _, ok := v.(*ssa.Range); !ok { // See https://github.com/golang/go/issues/19670 // (4.8) instructions use their types // (9.4) conversions use the type they convert to ctx.seeAndUse(v.Type(), fnObj, edgeType) g.typ(ctx, v.Type(), nil) } } switch instr := instr.(type) { case *ssa.Field: st := instr.X.Type().Underlying().(*types.Struct) field := st.Field(instr.Field) // (4.7) functions use fields they access ctx.seeAndUse(field, fnObj, edgeFieldAccess) case *ssa.FieldAddr: st := lintdsl.Dereference(instr.X.Type()).Underlying().(*types.Struct) field := st.Field(instr.Field) // (4.7) functions use fields they access ctx.seeAndUse(field, fnObj, edgeFieldAccess) case *ssa.Store: // nothing to do, handled generically by operands case *ssa.Call: c := instr.Common() if !c.IsInvoke() { // handled generically as an instruction operand if g.wholeProgram { // (e3) special case known reflection-based method callers switch lintdsl.CallName(c) { case "net/rpc.Register", "net/rpc.RegisterName", "(*net/rpc.Server).Register", "(*net/rpc.Server).RegisterName": var arg ssa.Value switch lintdsl.CallName(c) { case "net/rpc.Register": arg = c.Args[0] case "net/rpc.RegisterName": arg = c.Args[1] case "(*net/rpc.Server).Register": arg = c.Args[1] case "(*net/rpc.Server).RegisterName": arg = c.Args[2] } walkPhi(arg, func(v ssa.Value) { if v, ok := v.(*ssa.MakeInterface); ok { walkPhi(v.X, func(vv ssa.Value) { ms := ctx.pkg.SSA.Prog.MethodSets.MethodSet(vv.Type()) for i := 0; i < ms.Len(); i++ { if ms.At(i).Obj().Exported() { g.useMethod(ctx, vv.Type(), ms.At(i), fnObj, edgeNetRPCRegister) } } }) } }) } } } else { // (4.5) functions use functions/interface methods they call ctx.seeAndUse(c.Method, fnObj, edgeInterfaceCall) } case *ssa.Return: // nothing to do, handled generically by operands case *ssa.ChangeType: // conversion type handled generically s1, ok1 := lintdsl.Dereference(instr.Type()).Underlying().(*types.Struct) s2, ok2 := lintdsl.Dereference(instr.X.Type()).Underlying().(*types.Struct) if ok1 && ok2 { // Converting between two structs. The fields are // relevant for the conversion, but only if the // fields are also used outside of the conversion. // Mark fields as used by each other. assert(s1.NumFields() == s2.NumFields()) for i := 0; i < s1.NumFields(); i++ { ctx.see(s1.Field(i)) ctx.see(s2.Field(i)) // (5.1) when converting between two equivalent structs, the fields in // either struct use each other. the fields are relevant for the // conversion, but only if the fields are also accessed outside the // conversion. ctx.seeAndUse(s1.Field(i), s2.Field(i), edgeStructConversion) ctx.seeAndUse(s2.Field(i), s1.Field(i), edgeStructConversion) } } case *ssa.MakeInterface: // nothing to do, handled generically by operands case *ssa.Slice: // nothing to do, handled generically by operands case *ssa.RunDefers: // nothing to do, the deferred functions are already marked use by defering them. case *ssa.Convert: // to unsafe.Pointer if typ, ok := instr.Type().(*types.Basic); ok && typ.Kind() == types.UnsafePointer { if ptr, ok := instr.X.Type().Underlying().(*types.Pointer); ok { if st, ok := ptr.Elem().Underlying().(*types.Struct); ok { for i := 0; i < st.NumFields(); i++ { // (5.2) when converting to or from unsafe.Pointer, mark all fields as used. ctx.seeAndUse(st.Field(i), fnObj, edgeUnsafeConversion) } } } } // from unsafe.Pointer if typ, ok := instr.X.Type().(*types.Basic); ok && typ.Kind() == types.UnsafePointer { if ptr, ok := instr.Type().Underlying().(*types.Pointer); ok { if st, ok := ptr.Elem().Underlying().(*types.Struct); ok { for i := 0; i < st.NumFields(); i++ { // (5.2) when converting to or from unsafe.Pointer, mark all fields as used. ctx.seeAndUse(st.Field(i), fnObj, edgeUnsafeConversion) } } } } case *ssa.TypeAssert: // nothing to do, handled generically by instruction // type (possibly a tuple, which contains the asserted // to type). redundantly handled by the type of // ssa.Extract, too case *ssa.MakeClosure: // nothing to do, handled generically by operands case *ssa.Alloc: // nothing to do case *ssa.UnOp: // nothing to do case *ssa.BinOp: // nothing to do case *ssa.If: // nothing to do case *ssa.Jump: // nothing to do case *ssa.IndexAddr: // nothing to do case *ssa.Extract: // nothing to do case *ssa.Panic: // nothing to do case *ssa.DebugRef: // nothing to do case *ssa.BlankStore: // nothing to do case *ssa.Phi: // nothing to do case *ssa.MakeMap: // nothing to do case *ssa.MapUpdate: // nothing to do case *ssa.Lookup: // nothing to do case *ssa.MakeSlice: // nothing to do case *ssa.Send: // nothing to do case *ssa.MakeChan: // nothing to do case *ssa.Range: // nothing to do case *ssa.Next: // nothing to do case *ssa.Index: // nothing to do case *ssa.Select: // nothing to do case *ssa.ChangeInterface: // nothing to do case *ssa.Go: // nothing to do, handled generically by operands case *ssa.Defer: // nothing to do, handled generically by operands default: panic(fmt.Sprintf("unreachable: %T", instr)) } } } } // isNoCopyType reports whether a type represents the NoCopy sentinel // type. The NoCopy type is a named struct with no fields and exactly // one method `func Lock()` that is empty. // // FIXME(dh): currently we're not checking that the function body is // empty. func isNoCopyType(typ types.Type) bool { st, ok := typ.Underlying().(*types.Struct) if !ok { return false } if st.NumFields() != 0 { return false } named, ok := typ.(*types.Named) if !ok { return false } if named.NumMethods() != 1 { return false } meth := named.Method(0) if meth.Name() != "Lock" { return false } sig := meth.Type().(*types.Signature) if sig.Params().Len() != 0 || sig.Results().Len() != 0 { return false } return true } func walkPhi(v ssa.Value, fn func(v ssa.Value)) { phi, ok := v.(*ssa.Phi) if !ok { fn(v) return } seen := map[ssa.Value]struct{}{} var impl func(v *ssa.Phi) impl = func(v *ssa.Phi) { if _, ok := seen[v]; ok { return } seen[v] = struct{}{} for _, e := range v.Edges { if ev, ok := e.(*ssa.Phi); ok { impl(ev) } else { fn(e) } } } impl(phi) } func interfacesFromExportData(pkg *types.Package) []*types.Interface { var out []*types.Interface scope := pkg.Scope() for _, name := range scope.Names() { obj := scope.Lookup(name) out = append(out, interfacesFromObject(obj)...) } return out } func interfacesFromObject(obj types.Object) []*types.Interface { var out []*types.Interface switch obj := obj.(type) { case *types.Func: sig := obj.Type().(*types.Signature) for i := 0; i < sig.Results().Len(); i++ { out = append(out, interfacesFromObject(sig.Results().At(i))...) } for i := 0; i < sig.Params().Len(); i++ { out = append(out, interfacesFromObject(sig.Params().At(i))...) } case *types.TypeName: if named, ok := obj.Type().(*types.Named); ok { for i := 0; i < named.NumMethods(); i++ { out = append(out, interfacesFromObject(named.Method(i))...) } if iface, ok := named.Underlying().(*types.Interface); ok { out = append(out, iface) } } case *types.Var: // No call to Underlying here. We want unnamed interfaces // only. Named interfaces are gotten directly from the // package's scope. if iface, ok := obj.Type().(*types.Interface); ok { out = append(out, iface) } case *types.Const: case *types.Builtin: default: panic(fmt.Sprintf("unhandled type: %T", obj)) } return out }