| // Copyright 2012 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. |
| |
| // This file implements commonly used type predicates. |
| |
| package types2 |
| |
| // The isX predicates below report whether t is an X. |
| // If t is a type parameter the result is false; i.e., |
| // these predicates don't look inside a type parameter. |
| |
| func isBoolean(t Type) bool { return isBasic(t, IsBoolean) } |
| func isInteger(t Type) bool { return isBasic(t, IsInteger) } |
| func isUnsigned(t Type) bool { return isBasic(t, IsUnsigned) } |
| func isFloat(t Type) bool { return isBasic(t, IsFloat) } |
| func isComplex(t Type) bool { return isBasic(t, IsComplex) } |
| func isNumeric(t Type) bool { return isBasic(t, IsNumeric) } |
| func isString(t Type) bool { return isBasic(t, IsString) } |
| func isIntegerOrFloat(t Type) bool { return isBasic(t, IsInteger|IsFloat) } |
| func isConstType(t Type) bool { return isBasic(t, IsConstType) } |
| |
| // isBasic reports whether under(t) is a basic type with the specified info. |
| // If t is a type parameter the result is false; i.e., |
| // isBasic does not look inside a type parameter. |
| func isBasic(t Type, info BasicInfo) bool { |
| u, _ := under(t).(*Basic) |
| return u != nil && u.info&info != 0 |
| } |
| |
| // The allX predicates below report whether t is an X. |
| // If t is a type parameter the result is true if isX is true |
| // for all specified types of the type parameter's type set. |
| // allX is an optimized version of isX(coreType(t)) (which |
| // is the same as underIs(t, isX)). |
| |
| func allBoolean(t Type) bool { return allBasic(t, IsBoolean) } |
| func allInteger(t Type) bool { return allBasic(t, IsInteger) } |
| func allUnsigned(t Type) bool { return allBasic(t, IsUnsigned) } |
| func allNumeric(t Type) bool { return allBasic(t, IsNumeric) } |
| func allString(t Type) bool { return allBasic(t, IsString) } |
| func allOrdered(t Type) bool { return allBasic(t, IsOrdered) } |
| func allNumericOrString(t Type) bool { return allBasic(t, IsNumeric|IsString) } |
| |
| // allBasic reports whether under(t) is a basic type with the specified info. |
| // If t is a type parameter, the result is true if isBasic(t, info) is true |
| // for all specific types of the type parameter's type set. |
| // allBasic(t, info) is an optimized version of isBasic(coreType(t), info). |
| func allBasic(t Type, info BasicInfo) bool { |
| if tpar, _ := t.(*TypeParam); tpar != nil { |
| return tpar.is(func(t *term) bool { return t != nil && isBasic(t.typ, info) }) |
| } |
| return isBasic(t, info) |
| } |
| |
| // hasName reports whether t has a name. This includes |
| // predeclared types, defined types, and type parameters. |
| // hasName may be called with types that are not fully set up. |
| func hasName(t Type) bool { |
| switch t.(type) { |
| case *Basic, *Named, *TypeParam: |
| return true |
| } |
| return false |
| } |
| |
| // isTypeLit reports whether t is a type literal. |
| // This includes all non-defined types, but also basic types. |
| // isTypeLit may be called with types that are not fully set up. |
| func isTypeLit(t Type) bool { |
| switch t.(type) { |
| case *Named, *TypeParam: |
| return false |
| } |
| return true |
| } |
| |
| // isTyped reports whether t is typed; i.e., not an untyped |
| // constant or boolean. isTyped may be called with types that |
| // are not fully set up. |
| func isTyped(t Type) bool { |
| // isTyped is called with types that are not fully |
| // set up. Must not call under()! |
| b, _ := t.(*Basic) |
| return b == nil || b.info&IsUntyped == 0 |
| } |
| |
| // isUntyped(t) is the same as !isTyped(t). |
| func isUntyped(t Type) bool { |
| return !isTyped(t) |
| } |
| |
| // IsInterface reports whether t is an interface type. |
| func IsInterface(t Type) bool { |
| _, ok := under(t).(*Interface) |
| return ok |
| } |
| |
| // isNonTypeParamInterface reports whether t is an interface type but not a type parameter. |
| func isNonTypeParamInterface(t Type) bool { |
| return !isTypeParam(t) && IsInterface(t) |
| } |
| |
| // isTypeParam reports whether t is a type parameter. |
| func isTypeParam(t Type) bool { |
| _, ok := t.(*TypeParam) |
| return ok |
| } |
| |
| // hasEmptyTypeset reports whether t is a type parameter with an empty type set. |
| // The function does not force the computation of the type set and so is safe to |
| // use anywhere, but it may report a false negative if the type set has not been |
| // computed yet. |
| func hasEmptyTypeset(t Type) bool { |
| if tpar, _ := t.(*TypeParam); tpar != nil && tpar.bound != nil { |
| iface, _ := safeUnderlying(tpar.bound).(*Interface) |
| return iface != nil && iface.tset != nil && iface.tset.IsEmpty() |
| } |
| return false |
| } |
| |
| // isGeneric reports whether a type is a generic, uninstantiated type |
| // (generic signatures are not included). |
| // TODO(gri) should we include signatures or assert that they are not present? |
| func isGeneric(t Type) bool { |
| // A parameterized type is only generic if it doesn't have an instantiation already. |
| named, _ := t.(*Named) |
| return named != nil && named.obj != nil && named.inst == nil && named.TypeParams().Len() > 0 |
| } |
| |
| // Comparable reports whether values of type T are comparable. |
| func Comparable(T Type) bool { |
| return comparable(T, true, nil, nil) |
| } |
| |
| // If dynamic is set, non-type parameter interfaces are always comparable. |
| // If reportf != nil, it may be used to report why T is not comparable. |
| func comparable(T Type, dynamic bool, seen map[Type]bool, reportf func(string, ...interface{})) bool { |
| if seen[T] { |
| return true |
| } |
| if seen == nil { |
| seen = make(map[Type]bool) |
| } |
| seen[T] = true |
| |
| switch t := under(T).(type) { |
| case *Basic: |
| // assume invalid types to be comparable |
| // to avoid follow-up errors |
| return t.kind != UntypedNil |
| case *Pointer, *Chan: |
| return true |
| case *Struct: |
| for _, f := range t.fields { |
| if !comparable(f.typ, dynamic, seen, nil) { |
| if reportf != nil { |
| reportf("struct containing %s cannot be compared", f.typ) |
| } |
| return false |
| } |
| } |
| return true |
| case *Array: |
| if !comparable(t.elem, dynamic, seen, nil) { |
| if reportf != nil { |
| reportf("%s cannot be compared", t) |
| } |
| return false |
| } |
| return true |
| case *Interface: |
| if dynamic && !isTypeParam(T) || t.typeSet().IsComparable(seen) { |
| return true |
| } |
| if reportf != nil { |
| if t.typeSet().IsEmpty() { |
| reportf("empty type set") |
| } else { |
| reportf("incomparable types in type set") |
| } |
| } |
| // fallthrough |
| } |
| return false |
| } |
| |
| // hasNil reports whether type t includes the nil value. |
| func hasNil(t Type) bool { |
| switch u := under(t).(type) { |
| case *Basic: |
| return u.kind == UnsafePointer |
| case *Slice, *Pointer, *Signature, *Map, *Chan: |
| return true |
| case *Interface: |
| return !isTypeParam(t) || u.typeSet().underIs(func(u Type) bool { |
| return u != nil && hasNil(u) |
| }) |
| } |
| return false |
| } |
| |
| // An ifacePair is a node in a stack of interface type pairs compared for identity. |
| type ifacePair struct { |
| x, y *Interface |
| prev *ifacePair |
| } |
| |
| func (p *ifacePair) identical(q *ifacePair) bool { |
| return p.x == q.x && p.y == q.y || p.x == q.y && p.y == q.x |
| } |
| |
| // A comparer is used to compare types. |
| type comparer struct { |
| ignoreTags bool // if set, identical ignores struct tags |
| ignoreInvalids bool // if set, identical treats an invalid type as identical to any type |
| } |
| |
| // For changes to this code the corresponding changes should be made to unifier.nify. |
| func (c *comparer) identical(x, y Type, p *ifacePair) bool { |
| if x == y { |
| return true |
| } |
| |
| if c.ignoreInvalids && (x == Typ[Invalid] || y == Typ[Invalid]) { |
| return true |
| } |
| |
| switch x := x.(type) { |
| case *Basic: |
| // Basic types are singletons except for the rune and byte |
| // aliases, thus we cannot solely rely on the x == y check |
| // above. See also comment in TypeName.IsAlias. |
| if y, ok := y.(*Basic); ok { |
| return x.kind == y.kind |
| } |
| |
| case *Array: |
| // Two array types are identical if they have identical element types |
| // and the same array length. |
| if y, ok := y.(*Array); ok { |
| // If one or both array lengths are unknown (< 0) due to some error, |
| // assume they are the same to avoid spurious follow-on errors. |
| return (x.len < 0 || y.len < 0 || x.len == y.len) && c.identical(x.elem, y.elem, p) |
| } |
| |
| case *Slice: |
| // Two slice types are identical if they have identical element types. |
| if y, ok := y.(*Slice); ok { |
| return c.identical(x.elem, y.elem, p) |
| } |
| |
| case *Struct: |
| // Two struct types are identical if they have the same sequence of fields, |
| // and if corresponding fields have the same names, and identical types, |
| // and identical tags. Two embedded fields are considered to have the same |
| // name. Lower-case field names from different packages are always different. |
| if y, ok := y.(*Struct); ok { |
| if x.NumFields() == y.NumFields() { |
| for i, f := range x.fields { |
| g := y.fields[i] |
| if f.embedded != g.embedded || |
| !c.ignoreTags && x.Tag(i) != y.Tag(i) || |
| !f.sameId(g.pkg, g.name) || |
| !c.identical(f.typ, g.typ, p) { |
| return false |
| } |
| } |
| return true |
| } |
| } |
| |
| case *Pointer: |
| // Two pointer types are identical if they have identical base types. |
| if y, ok := y.(*Pointer); ok { |
| return c.identical(x.base, y.base, p) |
| } |
| |
| case *Tuple: |
| // Two tuples types are identical if they have the same number of elements |
| // and corresponding elements have identical types. |
| if y, ok := y.(*Tuple); ok { |
| if x.Len() == y.Len() { |
| if x != nil { |
| for i, v := range x.vars { |
| w := y.vars[i] |
| if !c.identical(v.typ, w.typ, p) { |
| return false |
| } |
| } |
| } |
| return true |
| } |
| } |
| |
| case *Signature: |
| y, _ := y.(*Signature) |
| if y == nil { |
| return false |
| } |
| |
| // Two function types are identical if they have the same number of |
| // parameters and result values, corresponding parameter and result types |
| // are identical, and either both functions are variadic or neither is. |
| // Parameter and result names are not required to match, and type |
| // parameters are considered identical modulo renaming. |
| |
| if x.TypeParams().Len() != y.TypeParams().Len() { |
| return false |
| } |
| |
| // In the case of generic signatures, we will substitute in yparams and |
| // yresults. |
| yparams := y.params |
| yresults := y.results |
| |
| if x.TypeParams().Len() > 0 { |
| // We must ignore type parameter names when comparing x and y. The |
| // easiest way to do this is to substitute x's type parameters for y's. |
| xtparams := x.TypeParams().list() |
| ytparams := y.TypeParams().list() |
| |
| var targs []Type |
| for i := range xtparams { |
| targs = append(targs, x.TypeParams().At(i)) |
| } |
| smap := makeSubstMap(ytparams, targs) |
| |
| var check *Checker // ok to call subst on a nil *Checker |
| ctxt := NewContext() // need a non-nil Context for the substitution below |
| |
| // Constraints must be pair-wise identical, after substitution. |
| for i, xtparam := range xtparams { |
| ybound := check.subst(nopos, ytparams[i].bound, smap, nil, ctxt) |
| if !c.identical(xtparam.bound, ybound, p) { |
| return false |
| } |
| } |
| |
| yparams = check.subst(nopos, y.params, smap, nil, ctxt).(*Tuple) |
| yresults = check.subst(nopos, y.results, smap, nil, ctxt).(*Tuple) |
| } |
| |
| return x.variadic == y.variadic && |
| c.identical(x.params, yparams, p) && |
| c.identical(x.results, yresults, p) |
| |
| case *Union: |
| if y, _ := y.(*Union); y != nil { |
| // TODO(rfindley): can this be reached during type checking? If so, |
| // consider passing a type set map. |
| unionSets := make(map[*Union]*_TypeSet) |
| xset := computeUnionTypeSet(nil, unionSets, nopos, x) |
| yset := computeUnionTypeSet(nil, unionSets, nopos, y) |
| return xset.terms.equal(yset.terms) |
| } |
| |
| case *Interface: |
| // Two interface types are identical if they describe the same type sets. |
| // With the existing implementation restriction, this simplifies to: |
| // |
| // Two interface types are identical if they have the same set of methods with |
| // the same names and identical function types, and if any type restrictions |
| // are the same. Lower-case method names from different packages are always |
| // different. The order of the methods is irrelevant. |
| if y, ok := y.(*Interface); ok { |
| xset := x.typeSet() |
| yset := y.typeSet() |
| if xset.comparable != yset.comparable { |
| return false |
| } |
| if !xset.terms.equal(yset.terms) { |
| return false |
| } |
| a := xset.methods |
| b := yset.methods |
| if len(a) == len(b) { |
| // Interface types are the only types where cycles can occur |
| // that are not "terminated" via named types; and such cycles |
| // can only be created via method parameter types that are |
| // anonymous interfaces (directly or indirectly) embedding |
| // the current interface. Example: |
| // |
| // type T interface { |
| // m() interface{T} |
| // } |
| // |
| // If two such (differently named) interfaces are compared, |
| // endless recursion occurs if the cycle is not detected. |
| // |
| // If x and y were compared before, they must be equal |
| // (if they were not, the recursion would have stopped); |
| // search the ifacePair stack for the same pair. |
| // |
| // This is a quadratic algorithm, but in practice these stacks |
| // are extremely short (bounded by the nesting depth of interface |
| // type declarations that recur via parameter types, an extremely |
| // rare occurrence). An alternative implementation might use a |
| // "visited" map, but that is probably less efficient overall. |
| q := &ifacePair{x, y, p} |
| for p != nil { |
| if p.identical(q) { |
| return true // same pair was compared before |
| } |
| p = p.prev |
| } |
| if debug { |
| assertSortedMethods(a) |
| assertSortedMethods(b) |
| } |
| for i, f := range a { |
| g := b[i] |
| if f.Id() != g.Id() || !c.identical(f.typ, g.typ, q) { |
| return false |
| } |
| } |
| return true |
| } |
| } |
| |
| case *Map: |
| // Two map types are identical if they have identical key and value types. |
| if y, ok := y.(*Map); ok { |
| return c.identical(x.key, y.key, p) && c.identical(x.elem, y.elem, p) |
| } |
| |
| case *Chan: |
| // Two channel types are identical if they have identical value types |
| // and the same direction. |
| if y, ok := y.(*Chan); ok { |
| return x.dir == y.dir && c.identical(x.elem, y.elem, p) |
| } |
| |
| case *Named: |
| // Two named types are identical if their type names originate |
| // in the same type declaration; if they are instantiated they |
| // must have identical type argument lists. |
| if y, ok := y.(*Named); ok { |
| // check type arguments before origins to match unifier |
| // (for correct source code we need to do all checks so |
| // order doesn't matter) |
| xargs := x.TypeArgs().list() |
| yargs := y.TypeArgs().list() |
| if len(xargs) != len(yargs) { |
| return false |
| } |
| for i, xarg := range xargs { |
| if !Identical(xarg, yargs[i]) { |
| return false |
| } |
| } |
| return indenticalOrigin(x, y) |
| } |
| |
| case *TypeParam: |
| // nothing to do (x and y being equal is caught in the very beginning of this function) |
| |
| case nil: |
| // avoid a crash in case of nil type |
| |
| default: |
| unreachable() |
| } |
| |
| return false |
| } |
| |
| // identicalOrigin reports whether x and y originated in the same declaration. |
| func indenticalOrigin(x, y *Named) bool { |
| // TODO(gri) is this correct? |
| return x.Origin().obj == y.Origin().obj |
| } |
| |
| // identicalInstance reports if two type instantiations are identical. |
| // Instantiations are identical if their origin and type arguments are |
| // identical. |
| func identicalInstance(xorig Type, xargs []Type, yorig Type, yargs []Type) bool { |
| if len(xargs) != len(yargs) { |
| return false |
| } |
| |
| for i, xa := range xargs { |
| if !Identical(xa, yargs[i]) { |
| return false |
| } |
| } |
| |
| return Identical(xorig, yorig) |
| } |
| |
| // Default returns the default "typed" type for an "untyped" type; |
| // it returns the incoming type for all other types. The default type |
| // for untyped nil is untyped nil. |
| func Default(t Type) Type { |
| if t, ok := t.(*Basic); ok { |
| switch t.kind { |
| case UntypedBool: |
| return Typ[Bool] |
| case UntypedInt: |
| return Typ[Int] |
| case UntypedRune: |
| return universeRune // use 'rune' name |
| case UntypedFloat: |
| return Typ[Float64] |
| case UntypedComplex: |
| return Typ[Complex128] |
| case UntypedString: |
| return Typ[String] |
| } |
| } |
| return t |
| } |
| |
| // maxType returns the "largest" type that encompasses both x and y. |
| // If x and y are different untyped numeric types, the result is the type of x or y |
| // that appears later in this list: integer, rune, floating-point, complex. |
| // Otherwise, if x != y, the result is nil. |
| func maxType(x, y Type) Type { |
| // We only care about untyped types (for now), so == is good enough. |
| // TODO(gri) investigate generalizing this function to simplify code elsewhere |
| if x == y { |
| return x |
| } |
| if isUntyped(x) && isUntyped(y) && isNumeric(x) && isNumeric(y) { |
| // untyped types are basic types |
| if x.(*Basic).kind > y.(*Basic).kind { |
| return x |
| } |
| return y |
| } |
| return nil |
| } |