// describe describes the syntax node denoted by the query position,
// including:
// - its syntactic category
// - the definition of its referent (for identifiers) [now redundant]
// - its type and method set (for an expression or type expression)
//
func describe(o *Oracle, qpos *QueryPos) (queryResult, error) {
if false { // debugging
fprintf(os.Stderr, o.fset, qpos.path[0], "you selected: %s %s",
astutil.NodeDescription(qpos.path[0]), pathToString(qpos.path))
}
path, action := findInterestingNode(qpos.info, qpos.path)
switch action {
case actionExpr:
return describeValue(o, qpos, path)
case actionType:
return describeType(o, qpos, path)
case actionPackage:
return describePackage(o, qpos, path)
case actionStmt:
return describeStmt(o, qpos, path)
case actionUnknown:
return &describeUnknownResult{path[0]}, nil
default:
panic(action) // unreachable
}
}
func (r *whatResult) display(printf printfFunc) {
for _, n := range r.path {
printf(n, "%s", astutil.NodeDescription(n))
}
printf(nil, "modes: %s", r.modes)
printf(nil, "srcdir: %s", r.srcdir)
printf(nil, "import path: %s", r.importPath)
}
// pointsto runs the pointer analysis on the selected expression,
// and reports its points-to set (for a pointer-like expression)
// or its dynamic types (for an interface, reflect.Value, or
// reflect.Type expression) and their points-to sets.
//
// All printed sets are sorted to ensure determinism.
//
func pointsto(o *Oracle, qpos *QueryPos) (queryResult, error) {
path, action := findInterestingNode(qpos.info, qpos.path)
if action != actionExpr {
return nil, fmt.Errorf("pointer analysis wants an expression; got %s",
astutil.NodeDescription(qpos.path[0]))
}
var expr ast.Expr
var obj types.Object
switch n := path[0].(type) {
case *ast.ValueSpec:
// ambiguous ValueSpec containing multiple names
return nil, fmt.Errorf("multiple value specification")
case *ast.Ident:
obj = qpos.info.ObjectOf(n)
expr = n
case ast.Expr:
expr = n
default:
// TODO(adonovan): is this reachable?
return nil, fmt.Errorf("unexpected AST for expr: %T", n)
}
// Reject non-pointerlike types (includes all constants---except nil).
// TODO(adonovan): reject nil too.
typ := qpos.info.TypeOf(expr)
if !pointer.CanPoint(typ) {
return nil, fmt.Errorf("pointer analysis wants an expression of reference type; got %s", typ)
}
// Determine the ssa.Value for the expression.
var value ssa.Value
var isAddr bool
var err error
if obj != nil {
// def/ref of func/var object
value, isAddr, err = ssaValueForIdent(o.prog, qpos.info, obj, path)
} else {
value, isAddr, err = ssaValueForExpr(o.prog, qpos.info, path)
}
if err != nil {
return nil, err // e.g. trivially dead code
}
// Run the pointer analysis.
ptrs, err := runPTA(o, value, isAddr)
if err != nil {
return nil, err // e.g. analytically unreachable
}
return &pointstoResult{
qpos: qpos,
typ: typ,
ptrs: ptrs,
}, nil
}
func (r *whatResult) toSerial(res *serial.Result, fset *token.FileSet) {
var enclosing []serial.SyntaxNode
for _, n := range r.path {
enclosing = append(enclosing, serial.SyntaxNode{
Description: astutil.NodeDescription(n),
Start: fset.Position(n.Pos()).Offset,
End: fset.Position(n.End()).Offset,
})
}
res.What = &serial.What{
Modes: r.modes,
SrcDir: r.srcdir,
ImportPath: r.importPath,
Enclosing: enclosing,
}
}
func describeStmt(o *Oracle, qpos *QueryPos, path []ast.Node) (*describeStmtResult, error) {
var description string
switch n := path[0].(type) {
case *ast.Ident:
if qpos.info.Defs[n] != nil {
description = "labelled statement"
} else {
description = "reference to labelled statement"
}
default:
// Nothing much to say about statements.
description = astutil.NodeDescription(n)
}
return &describeStmtResult{o.fset, path[0], description}, nil
}
// ParseQueryPos parses the source query position pos.
// If needExact, it must identify a single AST subtree;
// this is appropriate for queries that allow fairly arbitrary syntax,
// e.g. "describe".
//
func ParseQueryPos(iprog *loader.Program, posFlag string, needExact bool) (*QueryPos, error) {
filename, startOffset, endOffset, err := parsePosFlag(posFlag)
if err != nil {
return nil, err
}
start, end, err := findQueryPos(iprog.Fset, filename, startOffset, endOffset)
if err != nil {
return nil, err
}
info, path, exact := iprog.PathEnclosingInterval(start, end)
if path == nil {
return nil, fmt.Errorf("no syntax here")
}
if needExact && !exact {
return nil, fmt.Errorf("ambiguous selection within %s", astutil.NodeDescription(path[0]))
}
return &QueryPos{iprog.Fset, start, end, path, exact, info}, nil
}
func (r *describeValueResult) toSerial(res *serial.Result, fset *token.FileSet) {
var value, objpos string
if r.constVal != nil {
value = r.constVal.String()
}
if r.obj != nil {
objpos = fset.Position(r.obj.Pos()).String()
}
res.Describe = &serial.Describe{
Desc: astutil.NodeDescription(r.expr),
Pos: fset.Position(r.expr.Pos()).String(),
Detail: "value",
Value: &serial.DescribeValue{
Type: r.qpos.TypeString(r.typ),
Value: value,
ObjPos: objpos,
},
}
}
func (r *describeValueResult) display(printf printfFunc) {
var prefix, suffix string
if r.constVal != nil {
suffix = fmt.Sprintf(" of constant value %s", r.constVal)
}
switch obj := r.obj.(type) {
case *types.Func:
if recv := obj.Type().(*types.Signature).Recv(); recv != nil {
if _, ok := recv.Type().Underlying().(*types.Interface); ok {
prefix = "interface method "
} else {
prefix = "method "
}
}
}
// Describe the expression.
if r.obj != nil {
if r.obj.Pos() == r.expr.Pos() {
// defining ident
printf(r.expr, "definition of %s%s%s", prefix, r.qpos.ObjectString(r.obj), suffix)
} else {
// referring ident
printf(r.expr, "reference to %s%s%s", prefix, r.qpos.ObjectString(r.obj), suffix)
if def := r.obj.Pos(); def != token.NoPos {
printf(def, "defined here")
}
}
} else {
desc := astutil.NodeDescription(r.expr)
if suffix != "" {
// constant expression
printf(r.expr, "%s%s", desc, suffix)
} else {
// non-constant expression
printf(r.expr, "%s of type %s", desc, r.qpos.TypeString(r.typ))
}
}
}
// whicherrs takes an position to an error and tries to find all types, constants
// and global value which a given error can point to and which can be checked from the
// scope where the error lives.
// In short, it returns a list of things that can be checked against in order to handle
// an error properly.
//
// TODO(dmorsing): figure out if fields in errors like *os.PathError.Err
// can be queried recursively somehow.
func whicherrs(o *Oracle, qpos *QueryPos) (queryResult, error) {
path, action := findInterestingNode(qpos.info, qpos.path)
if action != actionExpr {
return nil, fmt.Errorf("whicherrs wants an expression; got %s",
astutil.NodeDescription(qpos.path[0]))
}
var expr ast.Expr
var obj types.Object
switch n := path[0].(type) {
case *ast.ValueSpec:
// ambiguous ValueSpec containing multiple names
return nil, fmt.Errorf("multiple value specification")
case *ast.Ident:
obj = qpos.info.ObjectOf(n)
expr = n
case ast.Expr:
expr = n
default:
return nil, fmt.Errorf("unexpected AST for expr: %T", n)
}
typ := qpos.info.TypeOf(expr)
if !types.Identical(typ, builtinErrorType) {
return nil, fmt.Errorf("selection is not an expression of type 'error'")
}
// Determine the ssa.Value for the expression.
var value ssa.Value
var err error
if obj != nil {
// def/ref of func/var object
value, _, err = ssaValueForIdent(o.prog, qpos.info, obj, path)
} else {
value, _, err = ssaValueForExpr(o.prog, qpos.info, path)
}
if err != nil {
return nil, err // e.g. trivially dead code
}
buildSSA(o)
globals := findVisibleErrs(o.prog, qpos)
constants := findVisibleConsts(o.prog, qpos)
res := &whicherrsResult{
qpos: qpos,
errpos: expr.Pos(),
}
// Find the instruction which initialized the
// global error. If more than one instruction has stored to the global
// remove the global from the set of values that we want to query.
allFuncs := ssautil.AllFunctions(o.prog)
for fn := range allFuncs {
for _, b := range fn.Blocks {
for _, instr := range b.Instrs {
store, ok := instr.(*ssa.Store)
if !ok {
continue
}
gval, ok := store.Addr.(*ssa.Global)
if !ok {
continue
}
gbl, ok := globals[gval]
if !ok {
continue
}
// we already found a store to this global
// The normal error define is just one store in the init
// so we just remove this global from the set we want to query
if gbl != nil {
delete(globals, gval)
}
globals[gval] = store.Val
}
}
}
o.ptaConfig.AddQuery(value)
for _, v := range globals {
o.ptaConfig.AddQuery(v)
}
ptares := ptrAnalysis(o)
valueptr := ptares.Queries[value]
for g, v := range globals {
ptr, ok := ptares.Queries[v]
if !ok {
continue
}
if !ptr.MayAlias(valueptr) {
continue
}
res.globals = append(res.globals, g)
}
pts := valueptr.PointsTo()
dedup := make(map[*ssa.NamedConst]bool)
for _, label := range pts.Labels() {
// These values are either MakeInterfaces or reflect
// generated interfaces. For the purposes of this
// analysis, we don't care about reflect generated ones
makeiface, ok := label.Value().(*ssa.MakeInterface)
if !ok {
continue
}
constval, ok := makeiface.X.(*ssa.Const)
if !ok {
continue
}
c := constants[*constval]
if c != nil && !dedup[c] {
dedup[c] = true
res.consts = append(res.consts, c)
}
}
concs := pts.DynamicTypes()
concs.Iterate(func(conc types.Type, _ interface{}) {
// go/types is a bit annoying here.
// We want to find all the types that we can
// typeswitch or assert to. This means finding out
// if the type pointed to can be seen by us.
//
// For the purposes of this analysis, the type is always
// either a Named type or a pointer to one.
// There are cases where error can be implemented
// by unnamed types, but in that case, we can't assert to
// it, so we don't care about it for this analysis.
var name *types.TypeName
switch t := conc.(type) {
case *types.Pointer:
named, ok := t.Elem().(*types.Named)
if !ok {
return
}
name = named.Obj()
case *types.Named:
name = t.Obj()
default:
return
}
if !isAccessibleFrom(name, qpos.info.Pkg) {
return
}
res.types = append(res.types, &errorType{conc, name})
})
sort.Sort(membersByPosAndString(res.globals))
sort.Sort(membersByPosAndString(res.consts))
sort.Sort(sorterrorType(res.types))
return res, nil
}
func (r *describeUnknownResult) toSerial(res *serial.Result, fset *token.FileSet) {
res.Describe = &serial.Describe{
Desc: astutil.NodeDescription(r.node),
Pos: fset.Position(r.node.Pos()).String(),
}
}
func (r *describeUnknownResult) display(printf printfFunc) {
// Nothing much to say about misc syntax.
printf(r.node, "%s", astutil.NodeDescription(r.node))
}