| // 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. |
| |
| // Package types declares the data types and implements |
| // the algorithms for type-checking of Go packages. Use |
| // Config.Check to invoke the type checker for a package. |
| // Alternatively, create a new type checker with NewChecker |
| // and invoke it incrementally by calling Checker.Files. |
| // |
| // Type-checking consists of several interdependent phases: |
| // |
| // Name resolution maps each identifier (syntax.Name) in the program to the |
| // language object (Object) it denotes. |
| // Use Info.{Defs,Uses,Implicits} for the results of name resolution. |
| // |
| // Constant folding computes the exact constant value (constant.Value) |
| // for every expression (syntax.Expr) that is a compile-time constant. |
| // Use Info.Types[expr].Value for the results of constant folding. |
| // |
| // Type inference computes the type (Type) of every expression (syntax.Expr) |
| // and checks for compliance with the language specification. |
| // Use Info.Types[expr].Type for the results of type inference. |
| // |
| package types2 |
| |
| import ( |
| "bytes" |
| "cmd/compile/internal/syntax" |
| "fmt" |
| "go/constant" |
| ) |
| |
| // An Error describes a type-checking error; it implements the error interface. |
| // A "soft" error is an error that still permits a valid interpretation of a |
| // package (such as "unused variable"); "hard" errors may lead to unpredictable |
| // behavior if ignored. |
| type Error struct { |
| Pos syntax.Pos // error position |
| Msg string // default error message, user-friendly |
| Full string // full error message, for debugging (may contain internal details) |
| Soft bool // if set, error is "soft" |
| } |
| |
| // Error returns an error string formatted as follows: |
| // filename:line:column: message |
| func (err Error) Error() string { |
| return fmt.Sprintf("%s: %s", err.Pos, err.Msg) |
| } |
| |
| // FullError returns an error string like Error, buy it may contain |
| // type-checker internal details such as subscript indices for type |
| // parameters and more. Useful for debugging. |
| func (err Error) FullError() string { |
| return fmt.Sprintf("%s: %s", err.Pos, err.Full) |
| } |
| |
| // An ArgumentError holds an error that is associated with an argument. |
| type ArgumentError struct { |
| index int |
| error |
| } |
| |
| // Index returns the positional index of the argument associated with the |
| // error. |
| func (e ArgumentError) Index() int { |
| return e.index |
| } |
| |
| // An Importer resolves import paths to Packages. |
| // |
| // CAUTION: This interface does not support the import of locally |
| // vendored packages. See https://golang.org/s/go15vendor. |
| // If possible, external implementations should implement ImporterFrom. |
| type Importer interface { |
| // Import returns the imported package for the given import path. |
| // The semantics is like for ImporterFrom.ImportFrom except that |
| // dir and mode are ignored (since they are not present). |
| Import(path string) (*Package, error) |
| } |
| |
| // ImportMode is reserved for future use. |
| type ImportMode int |
| |
| // An ImporterFrom resolves import paths to packages; it |
| // supports vendoring per https://golang.org/s/go15vendor. |
| // Use go/importer to obtain an ImporterFrom implementation. |
| type ImporterFrom interface { |
| // Importer is present for backward-compatibility. Calling |
| // Import(path) is the same as calling ImportFrom(path, "", 0); |
| // i.e., locally vendored packages may not be found. |
| // The types package does not call Import if an ImporterFrom |
| // is present. |
| Importer |
| |
| // ImportFrom returns the imported package for the given import |
| // path when imported by a package file located in dir. |
| // If the import failed, besides returning an error, ImportFrom |
| // is encouraged to cache and return a package anyway, if one |
| // was created. This will reduce package inconsistencies and |
| // follow-on type checker errors due to the missing package. |
| // The mode value must be 0; it is reserved for future use. |
| // Two calls to ImportFrom with the same path and dir must |
| // return the same package. |
| ImportFrom(path, dir string, mode ImportMode) (*Package, error) |
| } |
| |
| // A Config specifies the configuration for type checking. |
| // The zero value for Config is a ready-to-use default configuration. |
| type Config struct { |
| // GoVersion describes the accepted Go language version. The string |
| // must follow the format "go%d.%d" (e.g. "go1.12") or ist must be |
| // empty; an empty string indicates the latest language version. |
| // If the format is invalid, invoking the type checker will cause a |
| // panic. |
| GoVersion string |
| |
| // If IgnoreFuncBodies is set, function bodies are not |
| // type-checked. |
| IgnoreFuncBodies bool |
| |
| // If FakeImportC is set, `import "C"` (for packages requiring Cgo) |
| // declares an empty "C" package and errors are omitted for qualified |
| // identifiers referring to package C (which won't find an object). |
| // This feature is intended for the standard library cmd/api tool. |
| // |
| // Caution: Effects may be unpredictable due to follow-on errors. |
| // Do not use casually! |
| FakeImportC bool |
| |
| // If IgnoreLabels is set, correct label use is not checked. |
| // TODO(gri) Consolidate label checking and remove this flag. |
| IgnoreLabels bool |
| |
| // If CompilerErrorMessages is set, errors are reported using |
| // cmd/compile error strings to match $GOROOT/test errors. |
| // TODO(gri) Consolidate error messages and remove this flag. |
| CompilerErrorMessages bool |
| |
| // If AllowTypeLists is set, the type list syntax is permitted |
| // in an interface in addition to the type set syntax. |
| // TODO(gri) Remove once type lists are no longer supported by |
| // the parser. |
| AllowTypeLists bool |
| |
| // If go115UsesCgo is set, the type checker expects the |
| // _cgo_gotypes.go file generated by running cmd/cgo to be |
| // provided as a package source file. Qualified identifiers |
| // referring to package C will be resolved to cgo-provided |
| // declarations within _cgo_gotypes.go. |
| // |
| // It is an error to set both FakeImportC and go115UsesCgo. |
| go115UsesCgo bool |
| |
| // If Trace is set, a debug trace is printed to stdout. |
| Trace bool |
| |
| // If Error != nil, it is called with each error found |
| // during type checking; err has dynamic type Error. |
| // Secondary errors (for instance, to enumerate all types |
| // involved in an invalid recursive type declaration) have |
| // error strings that start with a '\t' character. |
| // If Error == nil, type-checking stops with the first |
| // error found. |
| Error func(err error) |
| |
| // An importer is used to import packages referred to from |
| // import declarations. |
| // If the installed importer implements ImporterFrom, the type |
| // checker calls ImportFrom instead of Import. |
| // The type checker reports an error if an importer is needed |
| // but none was installed. |
| Importer Importer |
| |
| // If Sizes != nil, it provides the sizing functions for package unsafe. |
| // Otherwise SizesFor("gc", "amd64") is used instead. |
| Sizes Sizes |
| |
| // If DisableUnusedImportCheck is set, packages are not checked |
| // for unused imports. |
| DisableUnusedImportCheck bool |
| } |
| |
| func srcimporter_setUsesCgo(conf *Config) { |
| conf.go115UsesCgo = true |
| } |
| |
| // Info holds result type information for a type-checked package. |
| // Only the information for which a map is provided is collected. |
| // If the package has type errors, the collected information may |
| // be incomplete. |
| type Info struct { |
| // Types maps expressions to their types, and for constant |
| // expressions, also their values. Invalid expressions are |
| // omitted. |
| // |
| // For (possibly parenthesized) identifiers denoting built-in |
| // functions, the recorded signatures are call-site specific: |
| // if the call result is not a constant, the recorded type is |
| // an argument-specific signature. Otherwise, the recorded type |
| // is invalid. |
| // |
| // The Types map does not record the type of every identifier, |
| // only those that appear where an arbitrary expression is |
| // permitted. For instance, the identifier f in a selector |
| // expression x.f is found only in the Selections map, the |
| // identifier z in a variable declaration 'var z int' is found |
| // only in the Defs map, and identifiers denoting packages in |
| // qualified identifiers are collected in the Uses map. |
| Types map[syntax.Expr]TypeAndValue |
| |
| // Inferred maps calls of parameterized functions that use |
| // type inference to the inferred type arguments and signature |
| // of the function called. The recorded "call" expression may be |
| // an *ast.CallExpr (as in f(x)), or an *ast.IndexExpr (s in f[T]). |
| Inferred map[syntax.Expr]Inferred |
| |
| // Defs maps identifiers to the objects they define (including |
| // package names, dots "." of dot-imports, and blank "_" identifiers). |
| // For identifiers that do not denote objects (e.g., the package name |
| // in package clauses, or symbolic variables t in t := x.(type) of |
| // type switch headers), the corresponding objects are nil. |
| // |
| // For an embedded field, Defs returns the field *Var it defines. |
| // |
| // Invariant: Defs[id] == nil || Defs[id].Pos() == id.Pos() |
| Defs map[*syntax.Name]Object |
| |
| // Uses maps identifiers to the objects they denote. |
| // |
| // For an embedded field, Uses returns the *TypeName it denotes. |
| // |
| // Invariant: Uses[id].Pos() != id.Pos() |
| Uses map[*syntax.Name]Object |
| |
| // Implicits maps nodes to their implicitly declared objects, if any. |
| // The following node and object types may appear: |
| // |
| // node declared object |
| // |
| // *syntax.ImportDecl *PkgName for imports without renames |
| // *syntax.CaseClause type-specific *Var for each type switch case clause (incl. default) |
| // *syntax.Field anonymous parameter *Var (incl. unnamed results) |
| // |
| Implicits map[syntax.Node]Object |
| |
| // Selections maps selector expressions (excluding qualified identifiers) |
| // to their corresponding selections. |
| Selections map[*syntax.SelectorExpr]*Selection |
| |
| // Scopes maps syntax.Nodes to the scopes they define. Package scopes are not |
| // associated with a specific node but with all files belonging to a package. |
| // Thus, the package scope can be found in the type-checked Package object. |
| // Scopes nest, with the Universe scope being the outermost scope, enclosing |
| // the package scope, which contains (one or more) files scopes, which enclose |
| // function scopes which in turn enclose statement and function literal scopes. |
| // Note that even though package-level functions are declared in the package |
| // scope, the function scopes are embedded in the file scope of the file |
| // containing the function declaration. |
| // |
| // The following node types may appear in Scopes: |
| // |
| // *syntax.File |
| // *syntax.FuncType |
| // *syntax.BlockStmt |
| // *syntax.IfStmt |
| // *syntax.SwitchStmt |
| // *syntax.CaseClause |
| // *syntax.CommClause |
| // *syntax.ForStmt |
| // |
| Scopes map[syntax.Node]*Scope |
| |
| // InitOrder is the list of package-level initializers in the order in which |
| // they must be executed. Initializers referring to variables related by an |
| // initialization dependency appear in topological order, the others appear |
| // in source order. Variables without an initialization expression do not |
| // appear in this list. |
| InitOrder []*Initializer |
| } |
| |
| // TypeOf returns the type of expression e, or nil if not found. |
| // Precondition: the Types, Uses and Defs maps are populated. |
| // |
| func (info *Info) TypeOf(e syntax.Expr) Type { |
| if t, ok := info.Types[e]; ok { |
| return t.Type |
| } |
| if id, _ := e.(*syntax.Name); id != nil { |
| if obj := info.ObjectOf(id); obj != nil { |
| return obj.Type() |
| } |
| } |
| return nil |
| } |
| |
| // ObjectOf returns the object denoted by the specified id, |
| // or nil if not found. |
| // |
| // If id is an embedded struct field, ObjectOf returns the field (*Var) |
| // it defines, not the type (*TypeName) it uses. |
| // |
| // Precondition: the Uses and Defs maps are populated. |
| // |
| func (info *Info) ObjectOf(id *syntax.Name) Object { |
| if obj := info.Defs[id]; obj != nil { |
| return obj |
| } |
| return info.Uses[id] |
| } |
| |
| // TypeAndValue reports the type and value (for constants) |
| // of the corresponding expression. |
| type TypeAndValue struct { |
| mode operandMode |
| Type Type |
| Value constant.Value |
| } |
| |
| // IsVoid reports whether the corresponding expression |
| // is a function call without results. |
| func (tv TypeAndValue) IsVoid() bool { |
| return tv.mode == novalue |
| } |
| |
| // IsType reports whether the corresponding expression specifies a type. |
| func (tv TypeAndValue) IsType() bool { |
| return tv.mode == typexpr |
| } |
| |
| // IsBuiltin reports whether the corresponding expression denotes |
| // a (possibly parenthesized) built-in function. |
| func (tv TypeAndValue) IsBuiltin() bool { |
| return tv.mode == builtin |
| } |
| |
| // IsValue reports whether the corresponding expression is a value. |
| // Builtins are not considered values. Constant values have a non- |
| // nil Value. |
| func (tv TypeAndValue) IsValue() bool { |
| switch tv.mode { |
| case constant_, variable, mapindex, value, nilvalue, commaok, commaerr: |
| return true |
| } |
| return false |
| } |
| |
| // IsNil reports whether the corresponding expression denotes the |
| // predeclared value nil. Depending on context, it may have been |
| // given a type different from UntypedNil. |
| func (tv TypeAndValue) IsNil() bool { |
| return tv.mode == nilvalue |
| } |
| |
| // Addressable reports whether the corresponding expression |
| // is addressable (https://golang.org/ref/spec#Address_operators). |
| func (tv TypeAndValue) Addressable() bool { |
| return tv.mode == variable |
| } |
| |
| // Assignable reports whether the corresponding expression |
| // is assignable to (provided a value of the right type). |
| func (tv TypeAndValue) Assignable() bool { |
| return tv.mode == variable || tv.mode == mapindex |
| } |
| |
| // HasOk reports whether the corresponding expression may be |
| // used on the rhs of a comma-ok assignment. |
| func (tv TypeAndValue) HasOk() bool { |
| return tv.mode == commaok || tv.mode == mapindex |
| } |
| |
| // Inferred reports the inferred type arguments and signature |
| // for a parameterized function call that uses type inference. |
| type Inferred struct { |
| TArgs *TypeList |
| Sig *Signature |
| } |
| |
| // An Initializer describes a package-level variable, or a list of variables in case |
| // of a multi-valued initialization expression, and the corresponding initialization |
| // expression. |
| type Initializer struct { |
| Lhs []*Var // var Lhs = Rhs |
| Rhs syntax.Expr |
| } |
| |
| func (init *Initializer) String() string { |
| var buf bytes.Buffer |
| for i, lhs := range init.Lhs { |
| if i > 0 { |
| buf.WriteString(", ") |
| } |
| buf.WriteString(lhs.Name()) |
| } |
| buf.WriteString(" = ") |
| syntax.Fprint(&buf, init.Rhs, syntax.ShortForm) |
| return buf.String() |
| } |
| |
| // Check type-checks a package and returns the resulting package object and |
| // the first error if any. Additionally, if info != nil, Check populates each |
| // of the non-nil maps in the Info struct. |
| // |
| // The package is marked as complete if no errors occurred, otherwise it is |
| // incomplete. See Config.Error for controlling behavior in the presence of |
| // errors. |
| // |
| // The package is specified by a list of *syntax.Files and corresponding |
| // file set, and the package path the package is identified with. |
| // The clean path must not be empty or dot ("."). |
| func (conf *Config) Check(path string, files []*syntax.File, info *Info) (*Package, error) { |
| pkg := NewPackage(path, "") |
| return pkg, NewChecker(conf, pkg, info).Files(files) |
| } |
| |
| // AssertableTo reports whether a value of type V can be asserted to have type T. |
| func AssertableTo(V *Interface, T Type) bool { |
| m, _ := (*Checker)(nil).assertableTo(V, T) |
| return m == nil |
| } |
| |
| // AssignableTo reports whether a value of type V is assignable to a variable of type T. |
| func AssignableTo(V, T Type) bool { |
| x := operand{mode: value, typ: V} |
| ok, _ := x.assignableTo(nil, T, nil) // check not needed for non-constant x |
| return ok |
| } |
| |
| // ConvertibleTo reports whether a value of type V is convertible to a value of type T. |
| func ConvertibleTo(V, T Type) bool { |
| x := operand{mode: value, typ: V} |
| return x.convertibleTo(nil, T) // check not needed for non-constant x |
| } |
| |
| // Implements reports whether type V implements interface T. |
| func Implements(V Type, T *Interface) bool { |
| f, _ := MissingMethod(V, T, true) |
| return f == nil |
| } |
| |
| // Identical reports whether x and y are identical types. |
| // Receivers of Signature types are ignored. |
| func Identical(x, y Type) bool { |
| return identical(x, y, true, nil) |
| } |
| |
| // IdenticalIgnoreTags reports whether x and y are identical types if tags are ignored. |
| // Receivers of Signature types are ignored. |
| func IdenticalIgnoreTags(x, y Type) bool { |
| return identical(x, y, false, nil) |
| } |