Esempio n. 1
0
// builtin type-checks a call to the built-in specified by id and
// returns true if the call is valid, with *x holding the result;
// but x.expr is not set. If the call is invalid, the result is
// false, and *x is undefined.
//
func (check *checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ bool) {
	// append is the only built-in that permits the use of ... for the last argument
	bin := predeclaredFuncs[id]
	if call.Ellipsis.IsValid() && id != _Append {
		check.invalidOp(call.Ellipsis, "invalid use of ... with built-in %s", bin.name)
		check.use(call.Args)
		return
	}

	// determine actual arguments
	var arg getter
	nargs := len(call.Args)
	switch id {
	default:
		// make argument getter
		arg, nargs, _ = unpack(func(x *operand, i int) { check.expr(x, call.Args[i]) }, nargs, false)
		// evaluate first argument, if present
		if nargs > 0 {
			arg(x, 0)
			if x.mode == invalid {
				return
			}
		}
	case _Make, _New, _Offsetof, _Trace:
		// arguments require special handling
	}

	// check argument count
	{
		msg := ""
		if nargs < bin.nargs {
			msg = "not enough"
		} else if !bin.variadic && nargs > bin.nargs {
			msg = "too many"
		}
		if msg != "" {
			check.invalidOp(call.Rparen, "%s arguments for %s (expected %d, found %d)", msg, call, bin.nargs, nargs)
			return
		}
	}

	switch id {
	case _Append:
		// append(s S, x ...T) S, where T is the element type of S
		// spec: "The variadic function append appends zero or more values x to s of type
		// S, which must be a slice type, and returns the resulting slice, also of type S.
		// The values x are passed to a parameter of type ...T where T is the element type
		// of S and the respective parameter passing rules apply."
		S := x.typ
		var T Type
		if s, _ := S.Underlying().(*Slice); s != nil {
			T = s.Elem
		} else {
			check.invalidArg(x.pos(), "%s is not a slice", x)
			return
		}

		// remember arguments that have been evaluated already
		alist := []operand{*x}

		// spec: "As a special case, append also accepts a first argument assignable
		// to type []byte with a second argument of string type followed by ... .
		// This form appends the bytes of the string.
		if nargs == 2 && call.Ellipsis.IsValid() && x.isAssignableTo(check.conf, NewSlice(universeByte)) {
			arg(x, 1)
			if x.mode == invalid {
				return
			}
			if isString(x.typ) {
				if check.Types != nil {
					sig := makeSig(S, S, NewSlice(universeByte))
					sig.IsVariadic = true
					check.recordBuiltinType(call.Fun, sig)
				}
				x.mode = value
				x.typ = S
				break
			}
			alist = append(alist, *x)
			// fallthrough
		}

		// check general case by creating custom signature
		sig := makeSig(S, S, NewSlice(T)) // []T required for variadic signature
		sig.IsVariadic = true
		check.arguments(x, call, sig, func(x *operand, i int) {
			// only evaluate arguments that have not been evaluated before
			if i < len(alist) {
				*x = alist[i]
				return
			}
			arg(x, i)
		}, nargs)
		// ok to continue even if check.arguments reported errors

		x.mode = value
		x.typ = S
		if check.Types != nil {
			check.recordBuiltinType(call.Fun, sig)
		}

	case _Cap, _Len:
		// cap(x)
		// len(x)
		mode := invalid
		var typ Type
		var val exact.Value
		switch typ = implicitArrayDeref(x.typ.Underlying()); t := typ.(type) {
		case *Basic:
			if isString(t) && id == _Len {
				if x.mode == constant {
					mode = constant
					val = exact.MakeInt64(int64(len(exact.StringVal(x.val))))
				} else {
					mode = value
				}
			}

		case *Array:
			mode = value
			// spec: "The expressions len(s) and cap(s) are constants
			// if the type of s is an array or pointer to an array and
			// the expression s does not contain channel receives or
			// function calls; in this case s is not evaluated."
			if !check.containsCallsOrReceives(x.expr) {
				mode = constant
				val = exact.MakeInt64(t.Len)
			}

		case *Slice, *Chan:
			mode = value

		case *Map:
			if id == _Len {
				mode = value
			}
		}

		if mode == invalid {
			check.invalidArg(x.pos(), "%s for %s", x, bin.name)
			return
		}

		x.mode = mode
		x.typ = Typ[Int]
		x.val = val
		if check.Types != nil && mode != constant {
			check.recordBuiltinType(call.Fun, makeSig(x.typ, typ))
		}

	case _Close:
		// close(c)
		c, _ := x.typ.Underlying().(*Chan)
		if c == nil {
			check.invalidArg(x.pos(), "%s is not a channel", x)
			return
		}
		if c.Dir == RecvOnly {
			check.invalidArg(x.pos(), "%s must not be a receive-only channel", x)
			return
		}

		x.mode = novalue
		if check.Types != nil {
			check.recordBuiltinType(call.Fun, makeSig(nil, c))
		}

	case _Complex:
		// complex(x, y realT) complexT
		if !check.complexArg(x) {
			return
		}

		var y operand
		arg(&y, 1)
		if y.mode == invalid {
			return
		}
		if !check.complexArg(&y) {
			return
		}

		check.convertUntyped(x, y.typ)
		if x.mode == invalid {
			return
		}
		check.convertUntyped(&y, x.typ)
		if y.mode == invalid {
			return
		}

		if !IsIdentical(x.typ, y.typ) {
			check.invalidArg(x.pos(), "mismatched types %s and %s", x.typ, y.typ)
			return
		}

		if x.mode == constant && y.mode == constant {
			x.val = exact.BinaryOp(x.val, token.ADD, exact.MakeImag(y.val))
		} else {
			x.mode = value
		}

		realT := x.typ
		complexT := Typ[Invalid]
		switch realT.Underlying().(*Basic).Kind {
		case Float32:
			complexT = Typ[Complex64]
		case Float64:
			complexT = Typ[Complex128]
		case UntypedInt, UntypedRune, UntypedFloat:
			if x.mode == constant {
				realT = defaultType(realT).(*Basic)
				complexT = Typ[UntypedComplex]
			} else {
				// untyped but not constant; probably because one
				// operand is a non-constant shift of untyped lhs
				realT = Typ[Float64]
				complexT = Typ[Complex128]
			}
		default:
			check.invalidArg(x.pos(), "float32 or float64 arguments expected")
			return
		}

		x.typ = complexT
		if check.Types != nil && x.mode != constant {
			check.recordBuiltinType(call.Fun, makeSig(complexT, realT, realT))
		}

		if x.mode != constant {
			// The arguments have now their final types, which at run-
			// time will be materialized. Update the expression trees.
			// If the current types are untyped, the materialized type
			// is the respective default type.
			// (If the result is constant, the arguments are never
			// materialized and there is nothing to do.)
			check.updateExprType(x.expr, realT, true)
			check.updateExprType(y.expr, realT, true)
		}

	case _Copy:
		// copy(x, y []T) int
		var dst Type
		if t, _ := x.typ.Underlying().(*Slice); t != nil {
			dst = t.Elem
		}

		var y operand
		arg(&y, 1)
		if y.mode == invalid {
			return
		}
		var src Type
		switch t := y.typ.Underlying().(type) {
		case *Basic:
			if isString(y.typ) {
				src = universeByte
			}
		case *Slice:
			src = t.Elem
		}

		if dst == nil || src == nil {
			check.invalidArg(x.pos(), "copy expects slice arguments; found %s and %s", x, &y)
			return
		}

		if !IsIdentical(dst, src) {
			check.invalidArg(x.pos(), "arguments to copy %s and %s have different element types %s and %s", x, &y, dst, src)
			return
		}

		x.mode = value
		x.typ = Typ[Int]
		if check.Types != nil {
			S := NewSlice(dst)
			check.recordBuiltinType(call.Fun, makeSig(x.typ, S, S))
		}

	case _Delete:
		// delete(m, k)
		m, _ := x.typ.Underlying().(*Map)
		if m == nil {
			check.invalidArg(x.pos(), "%s is not a map", x)
			return
		}
		arg(x, 1) // k
		if x.mode == invalid {
			return
		}

		if !x.isAssignableTo(check.conf, m.Key) {
			check.invalidArg(x.pos(), "%s is not assignable to %s", x, m.Key)
			return
		}

		x.mode = novalue
		if check.Types != nil {
			check.recordBuiltinType(call.Fun, makeSig(nil, m, m.Key))
		}

	case _Imag, _Real:
		// imag(complexT) realT
		// real(complexT) realT
		if !isComplex(x.typ) {
			check.invalidArg(x.pos(), "%s must be a complex number", x)
			return
		}
		if x.mode == constant {
			if id == _Real {
				x.val = exact.Real(x.val)
			} else {
				x.val = exact.Imag(x.val)
			}
		} else {
			x.mode = value
		}
		var k BasicKind
		switch x.typ.Underlying().(*Basic).Kind {
		case Complex64:
			k = Float32
		case Complex128:
			k = Float64
		case UntypedComplex:
			k = UntypedFloat
		default:
			unreachable()
		}

		if check.Types != nil && x.mode != constant {
			check.recordBuiltinType(call.Fun, makeSig(Typ[k], x.typ))
		}
		x.typ = Typ[k]

	case _Make:
		// make(T, n)
		// make(T, n, m)
		// (no argument evaluated yet)
		arg0 := call.Args[0]
		T := check.typ(arg0, nil, false)
		if T == Typ[Invalid] {
			return
		}
		var min int // minimum number of arguments
		switch T.Underlying().(type) {
		case *Slice:
			min = 2
		case *Map, *Chan:
			min = 1
		default:
			check.invalidArg(arg0.Pos(), "cannot make %s; type must be slice, map, or channel", arg0)
			return
		}
		if nargs < min || min+1 < nargs {
			check.errorf(call.Pos(), "%s expects %d or %d arguments; found %d", call, min, min+1, nargs)
			return
		}
		var sizes []int64 // constant integer arguments, if any
		for _, arg := range call.Args[1:] {
			if s, ok := check.index(arg, -1); ok && s >= 0 {
				sizes = append(sizes, s)
			}
		}
		if len(sizes) == 2 && sizes[0] > sizes[1] {
			check.invalidArg(call.Args[1].Pos(), "length and capacity swapped")
			// safe to continue
		}
		x.mode = variable
		x.typ = T
		if check.Types != nil {
			params := [...]Type{T, Typ[Int], Typ[Int]}
			check.recordBuiltinType(call.Fun, makeSig(x.typ, params[:1+len(sizes)]...))
		}

	case _New:
		// new(T)
		// (no argument evaluated yet)
		T := check.typ(call.Args[0], nil, false)
		if T == Typ[Invalid] {
			return
		}

		x.mode = variable
		x.typ = &Pointer{Elem: T}
		if check.Types != nil {
			check.recordBuiltinType(call.Fun, makeSig(x.typ, T))
		}

	case _Panic:
		// panic(x)
		T := new(Interface)
		if !check.assignment(x, T) {
			assert(x.mode == invalid)
			return
		}

		x.mode = novalue
		if check.Types != nil {
			check.recordBuiltinType(call.Fun, makeSig(nil, T))
		}

	case _Print, _Println:
		// print(x, y, ...)
		// println(x, y, ...)
		var params []Type
		if nargs > 0 {
			params = make([]Type, nargs)
			for i := 0; i < nargs; i++ {
				if i > 0 {
					arg(x, i) // first argument already evaluated
				}
				if !check.assignment(x, nil) {
					assert(x.mode == invalid)
					return
				}
				params[i] = x.typ
			}
		}

		x.mode = novalue
		if check.Types != nil {
			check.recordBuiltinType(call.Fun, makeSig(nil, params...))
		}

	case _Recover:
		// recover() interface{}
		x.mode = value
		x.typ = new(Interface)
		if check.Types != nil {
			check.recordBuiltinType(call.Fun, makeSig(x.typ))
		}

	case _Alignof:
		// unsafe.Alignof(x T) uintptr
		if !check.assignment(x, nil) {
			assert(x.mode == invalid)
			return
		}

		x.mode = constant
		x.val = exact.MakeInt64(check.conf.alignof(x.typ))
		x.typ = Typ[Uintptr]
		// result is constant - no need to record signature

	case _Offsetof:
		// unsafe.Offsetof(x T) uintptr, where x must be a selector
		// (no argument evaluated yet)
		arg0 := call.Args[0]
		selx, _ := unparen(arg0).(*ast.SelectorExpr)
		if selx == nil {
			check.invalidArg(arg0.Pos(), "%s is not a selector expression", arg0)
			check.rawExpr(x, arg0, nil) // evaluate to avoid spurious "declared but not used" errors
			return
		}
		check.expr(x, selx.X)
		if x.mode == invalid {
			return
		}
		base := derefStructPtr(x.typ)
		sel := selx.Sel.Name
		obj, index, indirect := LookupFieldOrMethod(base, check.pkg, sel)
		switch obj.(type) {
		case nil:
			check.invalidArg(x.pos(), "%s has no single field %s", base, sel)
			return
		case *Func:
			check.invalidArg(arg0.Pos(), "%s is a method value", arg0)
			return
		}
		if indirect {
			check.invalidArg(x.pos(), "field %s is embedded via a pointer in %s", sel, base)
			return
		}

		// TODO(gri) Should we pass x.typ instead of base (and indirect report if derefStructPtr indirected)?
		check.recordSelection(selx, FieldVal, base, obj, index, false)

		offs := check.conf.offsetof(base, index)
		x.mode = constant
		x.val = exact.MakeInt64(offs)
		x.typ = Typ[Uintptr]
		// result is constant - no need to record signature

	case _Sizeof:
		// unsafe.Sizeof(x T) uintptr
		if !check.assignment(x, nil) {
			assert(x.mode == invalid)
			return
		}

		x.mode = constant
		x.val = exact.MakeInt64(check.conf.sizeof(x.typ))
		x.typ = Typ[Uintptr]
		// result is constant - no need to record signature

	case _Assert:
		// assert(pred) causes a typechecker error if pred is false.
		// The result of assert is the value of pred if there is no error.
		// Note: assert is only available in self-test mode.
		if x.mode != constant || !isBoolean(x.typ) {
			check.invalidArg(x.pos(), "%s is not a boolean constant", x)
			return
		}
		if x.val.Kind() != exact.Bool {
			check.errorf(x.pos(), "internal error: value of %s should be a boolean constant", x)
			return
		}
		if !exact.BoolVal(x.val) {
			check.errorf(call.Pos(), "%s failed", call)
			// compile-time assertion failure - safe to continue
		}
		// result is constant - no need to record signature

	case _Trace:
		// trace(x, y, z, ...) dumps the positions, expressions, and
		// values of its arguments. The result of trace is the value
		// of the first argument.
		// Note: trace is only available in self-test mode.
		// (no argument evaluated yet)
		if nargs == 0 {
			check.dump("%s: trace() without arguments", call.Pos())
			x.mode = novalue
			break
		}
		var t operand
		x1 := x
		for _, arg := range call.Args {
			check.rawExpr(x1, arg, nil) // permit trace for types, e.g.: new(trace(T))
			check.dump("%s: %s", x1.pos(), x1)
			x1 = &t // use incoming x only for first argument
		}
		// trace is only available in test mode - no need to record signature

	default:
		unreachable()
	}

	return true
}
Esempio n. 2
0
func (check *checker) resolveFiles(files []*ast.File) {
	pkg := check.pkg

	// Phase 1: Pre-declare all package-level objects so that they can be found
	//          independent of source order. Associate methods with receiver
	//          base type names.

	var (
		objList []Object                     // list of package-level objects, in source order
		objMap  = make(map[Object]*declInfo) // corresponding declaration info
		initMap = make(map[Object]*declInfo) // declaration info for variables with initializers
	)

	// declare declares obj in the package scope, records its ident -> obj mapping,
	// and updates objList and objMap. The object must not be a function or method.
	declare := func(ident *ast.Ident, obj Object, d *declInfo) {
		assert(ident.Name == obj.GetName())

		// spec: "A package-scope or file-scope identifier with name init
		// may only be declared to be a function with this (func()) signature."
		if ident.Name == "init" {
			check.errorf(ident.Pos(), "cannot declare init - must be func")
			return
		}

		check.declare(pkg.scope, ident, obj)
		objList = append(objList, obj)
		objMap[obj] = d
	}

	importer := check.conf.Import
	if importer == nil {
		if DefaultImport == nil {
			panic(`no Config.Import or DefaultImport (missing import _ "golang.org/x/tools/go/gcimporter"?)`)
		}
		importer = DefaultImport
	}

	var (
		seenPkgs   = make(map[*Package]bool) // imported packages that have been seen already
		fileScopes []*Scope                  // file scope for each file
		dotImports []map[*Package]token.Pos  // positions of dot-imports for each file
	)

	for _, file := range files {
		// The package identifier denotes the current package,
		// but there is no corresponding package object.
		check.recordObject(file.Name, nil)

		fileScope := NewScope(pkg.scope)
		check.recordScope(file, fileScope)
		fileScopes = append(fileScopes, fileScope)
		dotImports = append(dotImports, nil) // element (map) is lazily allocated

		for _, decl := range file.Decls {
			switch d := decl.(type) {
			case *ast.BadDecl:
				// ignore

			case *ast.GenDecl:
				var last *ast.ValueSpec // last ValueSpec with type or init exprs seen
				for iota, spec := range d.Specs {
					switch s := spec.(type) {
					case *ast.ImportSpec:
						// import package
						var imp *Package
						path, err := check.validatedImportPath(s.Path.Value)
						if err != nil {
							check.errorf(s.Path.Pos(), "invalid import path (%s)", err)
							continue
						}
						if path == "C" && check.conf.FakeImportC {
							// TODO(gri) shouldn't create a new one each time
							imp = NewPackage("C", "C", NewScope(nil))
							imp.fake = true
						} else {
							var err error
							imp, err = importer(check.conf.Packages, path)
							if imp == nil && err == nil {
								err = errors.New("Config.Import returned nil but no error")
							}
							if err != nil {
								check.errorf(s.Path.Pos(), "could not import %s (%s)", path, err)
								continue
							}
						}

						// add package to list of explicit imports
						// (this functionality is provided as a convenience
						// for clients; it is not needed for type-checking)
						if !seenPkgs[imp] {
							seenPkgs[imp] = true
							if imp != Unsafe {
								pkg.Imports = append(pkg.Imports, imp)
							}
						}

						// local name overrides imported package name
						name := imp.Name
						if s.Name != nil {
							name = s.Name.Name
							if name == "init" {
								check.errorf(s.Name.Pos(), "cannot declare init - must be func")
								continue
							}
						}

						obj := NewPkgName(s.Pos(), imp, name)
						if s.Name != nil {
							// in a dot-import, the dot represents the package
							check.recordObject(s.Name, obj)
						} else {
							check.recordImplicit(s, obj)
						}

						// add import to file scope
						if name == "." {
							// merge imported scope with file scope
							for _, obj := range imp.scope.Objects {
								// A package scope may contain non-exported objects,
								// do not import them!
								if obj.IsExported() {
									// Note: This will change each imported object's scope!
									//       May be an issue for type aliases.
									check.declare(fileScope, nil, obj)
									check.recordImplicit(s, obj)
								}
							}
							// add position to set of dot-import positions for this file
							// (this is only needed for "imported but not used" errors)
							posSet := dotImports[len(dotImports)-1]
							if posSet == nil {
								posSet = make(map[*Package]token.Pos)
								dotImports[len(dotImports)-1] = posSet
							}
							posSet[imp] = s.Pos()
						} else {
							// declare imported package object in file scope
							check.declare(fileScope, nil, obj)
						}

					case *ast.ValueSpec:
						switch d.Tok {
						case token.CONST:
							// determine which initialization expressions to use
							switch {
							case s.Type != nil || len(s.Values) > 0:
								last = s
							case last == nil:
								last = new(ast.ValueSpec) // make sure last exists
							}

							// declare all constants
							for i, name := range s.Names {
								obj := NewConst(name.Pos(), pkg, name.Name, nil, exact.MakeInt64(int64(iota)))

								var init ast.Expr
								if i < len(last.Values) {
									init = last.Values[i]
								}

								declare(name, obj, &declInfo{file: fileScope, typ: last.Type, init: init})
							}

							check.arityMatch(s, last)

						case token.VAR:
							lhs := make([]*Var, len(s.Names))
							// If there's exactly one rhs initializer, use
							// the same declInfo d1 for all lhs variables
							// so that each lhs variable depends on the same
							// rhs initializer (n:1 var declaration).
							var d1 *declInfo
							if len(s.Values) == 1 {
								// The lhs elements are only set up after the foor loop below,
								// but that's ok because declareVar only collects the declInfo
								// for a later phase.
								d1 = &declInfo{file: fileScope, lhs: lhs, typ: s.Type, init: s.Values[0]}
							}

							// declare all variables
							for i, name := range s.Names {
								obj := NewVar(name.Pos(), pkg, name.Name, nil)
								lhs[i] = obj

								d := d1
								var init ast.Expr
								if d == nil {
									// individual assignments
									if i < len(s.Values) {
										init = s.Values[i]
									}
									d = &declInfo{file: fileScope, typ: s.Type, init: init}
								}

								declare(name, obj, d)

								// remember obj if it has an initializer
								if d1 != nil || init != nil {
									initMap[obj] = d
								}
							}

							check.arityMatch(s, nil)

						default:
							check.invalidAST(s.Pos(), "invalid token %s", d.Tok)
						}

					case *ast.TypeSpec:
						obj := NewTypeName(s.Name.Pos(), pkg, s.Name.Name, nil)
						declare(s.Name, obj, &declInfo{file: fileScope, typ: s.Type})

					default:
						check.invalidAST(s.Pos(), "unknown ast.Spec node %T", s)
					}
				}

			case *ast.FuncDecl:
				name := d.Name.Name
				obj := NewFunc(d.Name.Pos(), pkg, name, nil)
				if d.Recv == nil {
					// regular function
					if name == "init" {
						// don't declare init functions in the package scope - they are invisible
						obj.parent = pkg.scope
						check.recordObject(d.Name, obj)
						// init functions must have a body
						if d.Body == nil {
							check.errorf(obj.pos, "missing function body")
							// ok to continue
						}
					} else {
						check.declare(pkg.scope, d.Name, obj)
					}
				} else {
					// Associate method with receiver base type name, if possible.
					// Ignore methods that have an invalid receiver, or a blank _
					// receiver name. They will be type-checked later, with regular
					// functions.
					if list := d.Recv.List; len(list) > 0 {
						typ := list[0].Type
						if ptr, _ := typ.(*ast.StarExpr); ptr != nil {
							typ = ptr.X
						}
						if base, _ := typ.(*ast.Ident); base != nil && base.Name != "_" {
							check.methods[base.Name] = append(check.methods[base.Name], obj)
						}
					}
				}
				objList = append(objList, obj)
				info := &declInfo{file: fileScope, fdecl: d}
				objMap[obj] = info
				// remember obj if it has a body (= initializer)
				if d.Body != nil {
					initMap[obj] = info
				}

			default:
				check.invalidAST(d.Pos(), "unknown ast.Decl node %T", d)
			}
		}
	}
	seenPkgs = nil // not needed anymore

	// Phase 2: Verify that objects in package and file scopes have different names.

	for _, scope := range fileScopes {
		for _, obj := range scope.Objects {
			if alt := pkg.scope.Lookup(obj.GetName()); alt != nil {
				check.errorf(alt.Pos(), "%s already declared in this file through import of package %s", obj.GetName(), obj.GetPkg().Name)
			}
		}
	}

	// Phase 3: Typecheck all objects in objList, but not function bodies.

	check.objMap = objMap // indicate that we are checking package-level declarations (objects may not have a type yet)
	check.initMap = initMap
	for _, obj := range objList {
		if obj.GetType() == nil {
			check.objDecl(obj, nil, false)
		}
	}
	check.objMap = nil // done with package-level declarations

	// At this point we may have a non-empty check.methods map; this means that not all
	// entries were deleted at the end of typeDecl because the respective receiver base
	// types were not declared. In that case, an error was reported when declaring those
	// methods. We can now safely discard this map.
	check.methods = nil

	// Phase 4: Typecheck all functions bodies.

	for _, f := range check.funcList {
		check.decl = f.info
		check.funcBody(f.name, f.sig, f.body)
	}

	// Phase 5: Check initialization dependencies.
	// Note: must happen after checking all functions because function bodies
	// may introduce dependencies

	// For source order and reproducible error messages,
	// iterate through objList rather than initMap.
	for _, obj := range objList {
		if obj, _ := obj.(*Var); obj != nil {
			if init := initMap[obj]; init != nil {
				// provide non-nil path for re-use of underlying array
				check.dependencies(obj, init, make([]Object, 0, 8))
			}
		}
	}
	objList = nil       // not needed anymore
	check.initMap = nil // not needed anymore

	// Phase 6: Check for declared but not used packages and function variables.
	// Note: must happen after checking all functions because function bodies
	// may introduce package uses

	// If function bodies are not checked, packages' uses are likely missing,
	// and there are no unused function variables. Nothing left to do.
	if check.conf.IgnoreFuncBodies {
		return
	}

	// spec: "It is illegal (...) to directly import a package without referring to
	// any of its exported identifiers. To import a package solely for its side-effects
	// (initialization), use the blank identifier as explicit package name."
	for i, scope := range fileScopes {
		var usedDotImports map[*Package]bool // lazily allocated
		for _, obj := range scope.Objects {
			switch obj := obj.(type) {
			case *PkgName:
				// Unused "blank imports" are automatically ignored
				// since _ identifiers are not entered into scopes.
				if !obj.used {
					check.errorf(obj.pos, "%q imported but not used", obj.Pkg.Path)
				}
			default:
				// All other objects in the file scope must be dot-
				// imported. If an object was used, mark its package
				// as used.
				if obj.isUsed() {
					if usedDotImports == nil {
						usedDotImports = make(map[*Package]bool)
					}
					usedDotImports[obj.GetPkg()] = true
				}
			}
		}
		// Iterate through all dot-imports for this file and
		// check if the corresponding package was used.
		for pkg, pos := range dotImports[i] {
			if !usedDotImports[pkg] {
				check.errorf(pos, "%q imported but not used", pkg.Path)
			}
		}
	}
}
Esempio n. 3
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func (check *checker) declStmt(decl ast.Decl) {
	pkg := check.pkg

	switch d := decl.(type) {
	case *ast.BadDecl:
		// ignore

	case *ast.GenDecl:
		var last *ast.ValueSpec // last ValueSpec with type or init exprs seen
		for iota, spec := range d.Specs {
			switch s := spec.(type) {
			case *ast.ValueSpec:
				switch d.Tok {
				case token.CONST:
					// determine which init exprs to use
					switch {
					case s.Type != nil || len(s.Values) > 0:
						last = s
					case last == nil:
						last = new(ast.ValueSpec) // make sure last exists
					}

					// declare all constants
					lhs := make([]*Const, len(s.Names))
					for i, name := range s.Names {
						obj := NewConst(name.Pos(), pkg, name.Name, nil, exact.MakeInt64(int64(iota)))
						lhs[i] = obj

						var init ast.Expr
						if i < len(last.Values) {
							init = last.Values[i]
						}

						check.constDecl(obj, last.Type, init)
					}

					check.arityMatch(s, last)

					for i, name := range s.Names {
						check.declare(check.topScope, name, lhs[i])
					}

				case token.VAR:
					lhs0 := make([]*Var, len(s.Names))
					for i, name := range s.Names {
						lhs0[i] = NewVar(name.Pos(), pkg, name.Name, nil)
					}

					// initialize all variables
					for i, obj := range lhs0 {
						var lhs []*Var
						var init ast.Expr
						switch len(s.Values) {
						case len(s.Names):
							// lhs and rhs match
							init = s.Values[i]
						case 1:
							// rhs is expected to be a multi-valued expression
							lhs = lhs0
							init = s.Values[0]
						default:
							if i < len(s.Values) {
								init = s.Values[i]
							}
						}
						check.varDecl(obj, lhs, s.Type, init)
					}

					check.arityMatch(s, nil)

					// declare all variables
					// (only at this point are the variable scopes (parents) set)
					for i, name := range s.Names {
						check.declare(check.topScope, name, lhs0[i])
					}

				default:
					check.invalidAST(s.Pos(), "invalid token %s", d.Tok)
				}

			case *ast.TypeSpec:
				obj := NewTypeName(s.Name.Pos(), pkg, s.Name.Name, nil)
				check.declare(check.topScope, s.Name, obj)
				check.typeDecl(obj, s.Type, nil, false)

			default:
				check.invalidAST(s.Pos(), "const, type, or var declaration expected")
			}
		}

	default:
		check.invalidAST(d.Pos(), "unknown ast.Decl node %T", d)
	}
}
Esempio n. 4
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	res := NewVar(token.NoPos, nil, "", Typ[String])
	sig := &Signature{Results: []*Var{res}}
	err := NewFunc(token.NoPos, nil, "Error", sig)
	typ := &Named{UnderlyingT: NewInterface([]*Func{err}, nil), complete: true}
	sig.Recv = NewVar(token.NoPos, nil, "", typ)
	def(NewTypeName(token.NoPos, nil, "error", typ))
}

var predeclaredConsts = [...]struct {
	name string
	kind BasicKind
	val  exact.Value
}{
	{"true", UntypedBool, exact.MakeBool(true)},
	{"false", UntypedBool, exact.MakeBool(false)},
	{"iota", UntypedInt, exact.MakeInt64(0)},
}

func defPredeclaredConsts() {
	for _, c := range predeclaredConsts {
		def(NewConst(token.NoPos, nil, c.name, Typ[c.kind], c.val))
	}
}

func defPredeclaredNil() {
	def(&Nil{object{Name: "nil", Type: Typ[UntypedNil]}})
}

// A builtinId is the id of a builtin function.
type builtinId int