check.go

Documentation: go/types

		 1  // Copyright 2011 The Go Authors. All rights reserved.
		 2  // Use of this source code is governed by a BSD-style
		 3  // license that can be found in the LICENSE file.
		 4  
		 5  // This file implements the Check function, which drives type-checking.
		 6  
		 7  package types
		 8  
		 9  import (
		10  	"errors"
		11  	"fmt"
		12  	"go/ast"
		13  	"go/constant"
		14  	"go/token"
		15  )
		16  
		17  // debugging/development support
		18  const (
		19  	debug = false // leave on during development
		20  	trace = false // turn on for detailed type resolution traces
		21  )
		22  
		23  // If forceStrict is set, the type-checker enforces additional
		24  // rules not specified by the Go 1 spec, but which will
		25  // catch guaranteed run-time errors if the respective
		26  // code is executed. In other words, programs passing in
		27  // strict mode are Go 1 compliant, but not all Go 1 programs
		28  // will pass in strict mode. The additional rules are:
		29  //
		30  // - A type assertion x.(T) where T is an interface type
		31  //	 is invalid if any (statically known) method that exists
		32  //	 for both x and T have different signatures.
		33  //
		34  const forceStrict = false
		35  
		36  // exprInfo stores information about an untyped expression.
		37  type exprInfo struct {
		38  	isLhs bool // expression is lhs operand of a shift with delayed type-check
		39  	mode	operandMode
		40  	typ	 *Basic
		41  	val	 constant.Value // constant value; or nil (if not a constant)
		42  }
		43  
		44  // A context represents the context within which an object is type-checked.
		45  type context struct {
		46  	decl					*declInfo							// package-level declaration whose init expression/function body is checked
		47  	scope				 *Scope								 // top-most scope for lookups
		48  	pos					 token.Pos							// if valid, identifiers are looked up as if at position pos (used by Eval)
		49  	iota					constant.Value				 // value of iota in a constant declaration; nil otherwise
		50  	errpos				positioner						 // if set, identifier position of a constant with inherited initializer
		51  	sig					 *Signature						 // function signature if inside a function; nil otherwise
		52  	isPanic			 map[*ast.CallExpr]bool // set of panic call expressions (used for termination check)
		53  	hasLabel			bool									 // set if a function makes use of labels (only ~1% of functions); unused outside functions
		54  	hasCallOrRecv bool									 // set if an expression contains a function call or channel receive operation
		55  }
		56  
		57  // lookup looks up name in the current context and returns the matching object, or nil.
		58  func (ctxt *context) lookup(name string) Object {
		59  	_, obj := ctxt.scope.LookupParent(name, ctxt.pos)
		60  	return obj
		61  }
		62  
		63  // An importKey identifies an imported package by import path and source directory
		64  // (directory containing the file containing the import). In practice, the directory
		65  // may always be the same, or may not matter. Given an (import path, directory), an
		66  // importer must always return the same package (but given two different import paths,
		67  // an importer may still return the same package by mapping them to the same package
		68  // paths).
		69  type importKey struct {
		70  	path, dir string
		71  }
		72  
		73  // A dotImportKey describes a dot-imported object in the given scope.
		74  type dotImportKey struct {
		75  	scope *Scope
		76  	obj	 Object
		77  }
		78  
		79  // A Checker maintains the state of the type checker.
		80  // It must be created with NewChecker.
		81  type Checker struct {
		82  	// package information
		83  	// (initialized by NewChecker, valid for the life-time of checker)
		84  	conf *Config
		85  	fset *token.FileSet
		86  	pkg	*Package
		87  	*Info
		88  	version version										// accepted language version
		89  	objMap	map[Object]*declInfo			 // maps package-level objects and (non-interface) methods to declaration info
		90  	impMap	map[importKey]*Package		 // maps (import path, source directory) to (complete or fake) package
		91  	posMap	map[*Interface][]token.Pos // maps interface types to lists of embedded interface positions
		92  	typMap	map[string]*Named					// maps an instantiated named type hash to a *Named type
		93  
		94  	// pkgPathMap maps package names to the set of distinct import paths we've
		95  	// seen for that name, anywhere in the import graph. It is used for
		96  	// disambiguating package names in error messages.
		97  	//
		98  	// pkgPathMap is allocated lazily, so that we don't pay the price of building
		99  	// it on the happy path. seenPkgMap tracks the packages that we've already
	 100  	// walked.
	 101  	pkgPathMap map[string]map[string]bool
	 102  	seenPkgMap map[*Package]bool
	 103  
	 104  	// information collected during type-checking of a set of package files
	 105  	// (initialized by Files, valid only for the duration of check.Files;
	 106  	// maps and lists are allocated on demand)
	 107  	files				[]*ast.File							 // package files
	 108  	imports			[]*PkgName								// list of imported packages
	 109  	dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
	 110  
	 111  	firstErr error								 // first error encountered
	 112  	methods	map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
	 113  	untyped	map[ast.Expr]exprInfo // map of expressions without final type
	 114  	delayed	[]func()							// stack of delayed action segments; segments are processed in FIFO order
	 115  	objPath	[]Object							// path of object dependencies during type inference (for cycle reporting)
	 116  
	 117  	// context within which the current object is type-checked
	 118  	// (valid only for the duration of type-checking a specific object)
	 119  	context
	 120  
	 121  	// debugging
	 122  	indent int // indentation for tracing
	 123  }
	 124  
	 125  // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
	 126  func (check *Checker) addDeclDep(to Object) {
	 127  	from := check.decl
	 128  	if from == nil {
	 129  		return // not in a package-level init expression
	 130  	}
	 131  	if _, found := check.objMap[to]; !found {
	 132  		return // to is not a package-level object
	 133  	}
	 134  	from.addDep(to)
	 135  }
	 136  
	 137  func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
	 138  	m := check.untyped
	 139  	if m == nil {
	 140  		m = make(map[ast.Expr]exprInfo)
	 141  		check.untyped = m
	 142  	}
	 143  	m[e] = exprInfo{lhs, mode, typ, val}
	 144  }
	 145  
	 146  // later pushes f on to the stack of actions that will be processed later;
	 147  // either at the end of the current statement, or in case of a local constant
	 148  // or variable declaration, before the constant or variable is in scope
	 149  // (so that f still sees the scope before any new declarations).
	 150  func (check *Checker) later(f func()) {
	 151  	check.delayed = append(check.delayed, f)
	 152  }
	 153  
	 154  // push pushes obj onto the object path and returns its index in the path.
	 155  func (check *Checker) push(obj Object) int {
	 156  	check.objPath = append(check.objPath, obj)
	 157  	return len(check.objPath) - 1
	 158  }
	 159  
	 160  // pop pops and returns the topmost object from the object path.
	 161  func (check *Checker) pop() Object {
	 162  	i := len(check.objPath) - 1
	 163  	obj := check.objPath[i]
	 164  	check.objPath[i] = nil
	 165  	check.objPath = check.objPath[:i]
	 166  	return obj
	 167  }
	 168  
	 169  // NewChecker returns a new Checker instance for a given package.
	 170  // Package files may be added incrementally via checker.Files.
	 171  func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Checker {
	 172  	// make sure we have a configuration
	 173  	if conf == nil {
	 174  		conf = new(Config)
	 175  	}
	 176  
	 177  	// make sure we have an info struct
	 178  	if info == nil {
	 179  		info = new(Info)
	 180  	}
	 181  
	 182  	version, err := parseGoVersion(conf.goVersion)
	 183  	if err != nil {
	 184  		panic(fmt.Sprintf("invalid Go version %q (%v)", conf.goVersion, err))
	 185  	}
	 186  
	 187  	return &Checker{
	 188  		conf:		conf,
	 189  		fset:		fset,
	 190  		pkg:		 pkg,
	 191  		Info:		info,
	 192  		version: version,
	 193  		objMap:	make(map[Object]*declInfo),
	 194  		impMap:	make(map[importKey]*Package),
	 195  		posMap:	make(map[*Interface][]token.Pos),
	 196  		typMap:	make(map[string]*Named),
	 197  	}
	 198  }
	 199  
	 200  // initFiles initializes the files-specific portion of checker.
	 201  // The provided files must all belong to the same package.
	 202  func (check *Checker) initFiles(files []*ast.File) {
	 203  	// start with a clean slate (check.Files may be called multiple times)
	 204  	check.files = nil
	 205  	check.imports = nil
	 206  	check.dotImportMap = nil
	 207  
	 208  	check.firstErr = nil
	 209  	check.methods = nil
	 210  	check.untyped = nil
	 211  	check.delayed = nil
	 212  
	 213  	// determine package name and collect valid files
	 214  	pkg := check.pkg
	 215  	for _, file := range files {
	 216  		switch name := file.Name.Name; pkg.name {
	 217  		case "":
	 218  			if name != "_" {
	 219  				pkg.name = name
	 220  			} else {
	 221  				check.errorf(file.Name, _BlankPkgName, "invalid package name _")
	 222  			}
	 223  			fallthrough
	 224  
	 225  		case name:
	 226  			check.files = append(check.files, file)
	 227  
	 228  		default:
	 229  			check.errorf(atPos(file.Package), _MismatchedPkgName, "package %s; expected %s", name, pkg.name)
	 230  			// ignore this file
	 231  		}
	 232  	}
	 233  }
	 234  
	 235  // A bailout panic is used for early termination.
	 236  type bailout struct{}
	 237  
	 238  func (check *Checker) handleBailout(err *error) {
	 239  	switch p := recover().(type) {
	 240  	case nil, bailout:
	 241  		// normal return or early exit
	 242  		*err = check.firstErr
	 243  	default:
	 244  		// re-panic
	 245  		panic(p)
	 246  	}
	 247  }
	 248  
	 249  // Files checks the provided files as part of the checker's package.
	 250  func (check *Checker) Files(files []*ast.File) error { return check.checkFiles(files) }
	 251  
	 252  var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
	 253  
	 254  func (check *Checker) checkFiles(files []*ast.File) (err error) {
	 255  	if check.conf.FakeImportC && check.conf.go115UsesCgo {
	 256  		return errBadCgo
	 257  	}
	 258  
	 259  	defer check.handleBailout(&err)
	 260  
	 261  	check.initFiles(files)
	 262  
	 263  	check.collectObjects()
	 264  
	 265  	check.packageObjects()
	 266  
	 267  	check.processDelayed(0) // incl. all functions
	 268  
	 269  	check.initOrder()
	 270  
	 271  	if !check.conf.DisableUnusedImportCheck {
	 272  		check.unusedImports()
	 273  	}
	 274  
	 275  	check.recordUntyped()
	 276  
	 277  	if check.Info != nil {
	 278  		sanitizeInfo(check.Info)
	 279  	}
	 280  
	 281  	check.pkg.complete = true
	 282  
	 283  	// no longer needed - release memory
	 284  	check.imports = nil
	 285  	check.dotImportMap = nil
	 286  	check.pkgPathMap = nil
	 287  	check.seenPkgMap = nil
	 288  
	 289  	// TODO(rFindley) There's more memory we should release at this point.
	 290  
	 291  	return
	 292  }
	 293  
	 294  // processDelayed processes all delayed actions pushed after top.
	 295  func (check *Checker) processDelayed(top int) {
	 296  	// If each delayed action pushes a new action, the
	 297  	// stack will continue to grow during this loop.
	 298  	// However, it is only processing functions (which
	 299  	// are processed in a delayed fashion) that may
	 300  	// add more actions (such as nested functions), so
	 301  	// this is a sufficiently bounded process.
	 302  	for i := top; i < len(check.delayed); i++ {
	 303  		check.delayed[i]() // may append to check.delayed
	 304  	}
	 305  	assert(top <= len(check.delayed)) // stack must not have shrunk
	 306  	check.delayed = check.delayed[:top]
	 307  }
	 308  
	 309  func (check *Checker) record(x *operand) {
	 310  	// convert x into a user-friendly set of values
	 311  	// TODO(gri) this code can be simplified
	 312  	var typ Type
	 313  	var val constant.Value
	 314  	switch x.mode {
	 315  	case invalid:
	 316  		typ = Typ[Invalid]
	 317  	case novalue:
	 318  		typ = (*Tuple)(nil)
	 319  	case constant_:
	 320  		typ = x.typ
	 321  		val = x.val
	 322  	default:
	 323  		typ = x.typ
	 324  	}
	 325  	assert(x.expr != nil && typ != nil)
	 326  
	 327  	if isUntyped(typ) {
	 328  		// delay type and value recording until we know the type
	 329  		// or until the end of type checking
	 330  		check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
	 331  	} else {
	 332  		check.recordTypeAndValue(x.expr, x.mode, typ, val)
	 333  	}
	 334  }
	 335  
	 336  func (check *Checker) recordUntyped() {
	 337  	if !debug && check.Types == nil {
	 338  		return // nothing to do
	 339  	}
	 340  
	 341  	for x, info := range check.untyped {
	 342  		if debug && isTyped(info.typ) {
	 343  			check.dump("%v: %s (type %s) is typed", x.Pos(), x, info.typ)
	 344  			unreachable()
	 345  		}
	 346  		check.recordTypeAndValue(x, info.mode, info.typ, info.val)
	 347  	}
	 348  }
	 349  
	 350  func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) {
	 351  	assert(x != nil)
	 352  	assert(typ != nil)
	 353  	if mode == invalid {
	 354  		return // omit
	 355  	}
	 356  	if mode == constant_ {
	 357  		assert(val != nil)
	 358  		// We check is(typ, IsConstType) here as constant expressions may be
	 359  		// recorded as type parameters.
	 360  		assert(typ == Typ[Invalid] || is(typ, IsConstType))
	 361  	}
	 362  	if m := check.Types; m != nil {
	 363  		m[x] = TypeAndValue{mode, typ, val}
	 364  	}
	 365  }
	 366  
	 367  func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) {
	 368  	// f must be a (possibly parenthesized, possibly qualified)
	 369  	// identifier denoting a built-in (including unsafe's non-constant
	 370  	// functions Add and Slice): record the signature for f and possible
	 371  	// children.
	 372  	for {
	 373  		check.recordTypeAndValue(f, builtin, sig, nil)
	 374  		switch p := f.(type) {
	 375  		case *ast.Ident, *ast.SelectorExpr:
	 376  			return // we're done
	 377  		case *ast.ParenExpr:
	 378  			f = p.X
	 379  		default:
	 380  			unreachable()
	 381  		}
	 382  	}
	 383  }
	 384  
	 385  func (check *Checker) recordCommaOkTypes(x ast.Expr, a [2]Type) {
	 386  	assert(x != nil)
	 387  	if a[0] == nil || a[1] == nil {
	 388  		return
	 389  	}
	 390  	assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
	 391  	if m := check.Types; m != nil {
	 392  		for {
	 393  			tv := m[x]
	 394  			assert(tv.Type != nil) // should have been recorded already
	 395  			pos := x.Pos()
	 396  			tv.Type = NewTuple(
	 397  				NewVar(pos, check.pkg, "", a[0]),
	 398  				NewVar(pos, check.pkg, "", a[1]),
	 399  			)
	 400  			m[x] = tv
	 401  			// if x is a parenthesized expression (p.X), update p.X
	 402  			p, _ := x.(*ast.ParenExpr)
	 403  			if p == nil {
	 404  				break
	 405  			}
	 406  			x = p.X
	 407  		}
	 408  	}
	 409  }
	 410  
	 411  func (check *Checker) recordInferred(call ast.Expr, targs []Type, sig *Signature) {
	 412  	assert(call != nil)
	 413  	assert(sig != nil)
	 414  	if m := getInferred(check.Info); m != nil {
	 415  		m[call] = _Inferred{targs, sig}
	 416  	}
	 417  }
	 418  
	 419  func (check *Checker) recordDef(id *ast.Ident, obj Object) {
	 420  	assert(id != nil)
	 421  	if m := check.Defs; m != nil {
	 422  		m[id] = obj
	 423  	}
	 424  }
	 425  
	 426  func (check *Checker) recordUse(id *ast.Ident, obj Object) {
	 427  	assert(id != nil)
	 428  	assert(obj != nil)
	 429  	if m := check.Uses; m != nil {
	 430  		m[id] = obj
	 431  	}
	 432  }
	 433  
	 434  func (check *Checker) recordImplicit(node ast.Node, obj Object) {
	 435  	assert(node != nil)
	 436  	assert(obj != nil)
	 437  	if m := check.Implicits; m != nil {
	 438  		m[node] = obj
	 439  	}
	 440  }
	 441  
	 442  func (check *Checker) recordSelection(x *ast.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
	 443  	assert(obj != nil && (recv == nil || len(index) > 0))
	 444  	check.recordUse(x.Sel, obj)
	 445  	if m := check.Selections; m != nil {
	 446  		m[x] = &Selection{kind, recv, obj, index, indirect}
	 447  	}
	 448  }
	 449  
	 450  func (check *Checker) recordScope(node ast.Node, scope *Scope) {
	 451  	assert(node != nil)
	 452  	assert(scope != nil)
	 453  	if m := check.Scopes; m != nil {
	 454  		m[node] = scope
	 455  	}
	 456  }
	 457
View as plain text