mirror of https://go.googlesource.com/go
478 lines
17 KiB
Go
478 lines
17 KiB
Go
// Copyright 2012 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package types declares the data types and implements
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// the algorithms for type-checking of Go packages. Use
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// [Config.Check] to invoke the type checker for a package.
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// Alternatively, create a new type checker with [NewChecker]
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// and invoke it incrementally by calling [Checker.Files].
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//
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// Type-checking consists of several interdependent phases:
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//
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// Name resolution maps each identifier ([ast.Ident]) in the program
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// to the symbol ([Object]) it denotes. Use the Defs and Uses fields
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// of [Info] or the [Info.ObjectOf] method to find the symbol for an
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// identifier, and use the Implicits field of [Info] to find the
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// symbol for certain other kinds of syntax node.
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//
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// Constant folding computes the exact constant value
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// ([constant.Value]) of every expression ([ast.Expr]) that is a
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// compile-time constant. Use the Types field of [Info] to find the
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// results of constant folding for an expression.
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//
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// Type deduction computes the type ([Type]) of every expression
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// ([ast.Expr]) and checks for compliance with the language
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// specification. Use the Types field of [Info] for the results of
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// type deduction.
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//
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// For a tutorial, see https://go.dev/s/types-tutorial.
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package types
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import (
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"bytes"
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"fmt"
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"go/ast"
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"go/constant"
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"go/token"
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. "internal/types/errors"
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_ "unsafe" // for linkname
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)
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// An Error describes a type-checking error; it implements the error interface.
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// A "soft" error is an error that still permits a valid interpretation of a
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// package (such as "unused variable"); "hard" errors may lead to unpredictable
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// behavior if ignored.
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type Error struct {
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Fset *token.FileSet // file set for interpretation of Pos
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Pos token.Pos // error position
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Msg string // error message
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Soft bool // if set, error is "soft"
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// go116code is a future API, unexported as the set of error codes is large
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// and likely to change significantly during experimentation. Tools wishing
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// to preview this feature may read go116code using reflection (see
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// errorcodes_test.go), but beware that there is no guarantee of future
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// compatibility.
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go116code Code
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go116start token.Pos
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go116end token.Pos
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}
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// Error returns an error string formatted as follows:
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// filename:line:column: message
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func (err Error) Error() string {
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return fmt.Sprintf("%s: %s", err.Fset.Position(err.Pos), err.Msg)
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}
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// An ArgumentError holds an error associated with an argument index.
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type ArgumentError struct {
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Index int
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Err error
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}
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func (e *ArgumentError) Error() string { return e.Err.Error() }
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func (e *ArgumentError) Unwrap() error { return e.Err }
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// An Importer resolves import paths to Packages.
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//
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// CAUTION: This interface does not support the import of locally
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// vendored packages. See https://golang.org/s/go15vendor.
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// If possible, external implementations should implement [ImporterFrom].
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type Importer interface {
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// Import returns the imported package for the given import path.
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// The semantics is like for ImporterFrom.ImportFrom except that
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// dir and mode are ignored (since they are not present).
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Import(path string) (*Package, error)
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}
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// ImportMode is reserved for future use.
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type ImportMode int
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// An ImporterFrom resolves import paths to packages; it
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// supports vendoring per https://golang.org/s/go15vendor.
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// Use go/importer to obtain an ImporterFrom implementation.
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type ImporterFrom interface {
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// Importer is present for backward-compatibility. Calling
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// Import(path) is the same as calling ImportFrom(path, "", 0);
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// i.e., locally vendored packages may not be found.
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// The types package does not call Import if an ImporterFrom
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// is present.
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Importer
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// ImportFrom returns the imported package for the given import
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// path when imported by a package file located in dir.
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// If the import failed, besides returning an error, ImportFrom
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// is encouraged to cache and return a package anyway, if one
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// was created. This will reduce package inconsistencies and
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// follow-on type checker errors due to the missing package.
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// The mode value must be 0; it is reserved for future use.
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// Two calls to ImportFrom with the same path and dir must
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// return the same package.
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ImportFrom(path, dir string, mode ImportMode) (*Package, error)
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}
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// A Config specifies the configuration for type checking.
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// The zero value for Config is a ready-to-use default configuration.
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type Config struct {
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// Context is the context used for resolving global identifiers. If nil, the
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// type checker will initialize this field with a newly created context.
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Context *Context
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// GoVersion describes the accepted Go language version. The string must
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// start with a prefix of the form "go%d.%d" (e.g. "go1.20", "go1.21rc1", or
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// "go1.21.0") or it must be empty; an empty string disables Go language
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// version checks. If the format is invalid, invoking the type checker will
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// result in an error.
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GoVersion string
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// If IgnoreFuncBodies is set, function bodies are not
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// type-checked.
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IgnoreFuncBodies bool
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// If FakeImportC is set, `import "C"` (for packages requiring Cgo)
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// declares an empty "C" package and errors are omitted for qualified
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// identifiers referring to package C (which won't find an object).
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// This feature is intended for the standard library cmd/api tool.
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//
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// Caution: Effects may be unpredictable due to follow-on errors.
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// Do not use casually!
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FakeImportC bool
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// If go115UsesCgo is set, the type checker expects the
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// _cgo_gotypes.go file generated by running cmd/cgo to be
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// provided as a package source file. Qualified identifiers
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// referring to package C will be resolved to cgo-provided
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// declarations within _cgo_gotypes.go.
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//
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// It is an error to set both FakeImportC and go115UsesCgo.
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go115UsesCgo bool
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// If _Trace is set, a debug trace is printed to stdout.
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_Trace bool
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// If Error != nil, it is called with each error found
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// during type checking; err has dynamic type Error.
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// Secondary errors (for instance, to enumerate all types
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// involved in an invalid recursive type declaration) have
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// error strings that start with a '\t' character.
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// If Error == nil, type-checking stops with the first
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// error found.
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Error func(err error)
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// An importer is used to import packages referred to from
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// import declarations.
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// If the installed importer implements ImporterFrom, the type
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// checker calls ImportFrom instead of Import.
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// The type checker reports an error if an importer is needed
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// but none was installed.
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Importer Importer
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// If Sizes != nil, it provides the sizing functions for package unsafe.
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// Otherwise SizesFor("gc", "amd64") is used instead.
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Sizes Sizes
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// If DisableUnusedImportCheck is set, packages are not checked
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// for unused imports.
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DisableUnusedImportCheck bool
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// If a non-empty _ErrorURL format string is provided, it is used
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// to format an error URL link that is appended to the first line
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// of an error message. ErrorURL must be a format string containing
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// exactly one "%s" format, e.g. "[go.dev/e/%s]".
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_ErrorURL string
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// If EnableAlias is set, alias declarations produce an Alias type. Otherwise
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// the alias information is only in the type name, which points directly to
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// the actual (aliased) type.
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//
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// This setting must not differ among concurrent type-checking operations,
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// since it affects the behavior of Universe.Lookup("any").
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//
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// This flag will eventually be removed (with Go 1.24 at the earliest).
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_EnableAlias bool
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}
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// Linkname for use from srcimporter.
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//go:linkname srcimporter_setUsesCgo
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func srcimporter_setUsesCgo(conf *Config) {
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conf.go115UsesCgo = true
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}
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// Info holds result type information for a type-checked package.
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// Only the information for which a map is provided is collected.
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// If the package has type errors, the collected information may
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// be incomplete.
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type Info struct {
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// Types maps expressions to their types, and for constant
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// expressions, also their values. Invalid expressions are
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// omitted.
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//
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// For (possibly parenthesized) identifiers denoting built-in
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// functions, the recorded signatures are call-site specific:
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// if the call result is not a constant, the recorded type is
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// an argument-specific signature. Otherwise, the recorded type
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// is invalid.
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//
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// The Types map does not record the type of every identifier,
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// only those that appear where an arbitrary expression is
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// permitted. For instance, the identifier f in a selector
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// expression x.f is found only in the Selections map, the
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// identifier z in a variable declaration 'var z int' is found
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// only in the Defs map, and identifiers denoting packages in
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// qualified identifiers are collected in the Uses map.
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Types map[ast.Expr]TypeAndValue
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// Instances maps identifiers denoting generic types or functions to their
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// type arguments and instantiated type.
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//
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// For example, Instances will map the identifier for 'T' in the type
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// instantiation T[int, string] to the type arguments [int, string] and
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// resulting instantiated *Named type. Given a generic function
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// func F[A any](A), Instances will map the identifier for 'F' in the call
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// expression F(int(1)) to the inferred type arguments [int], and resulting
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// instantiated *Signature.
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//
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// Invariant: Instantiating Uses[id].Type() with Instances[id].TypeArgs
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// results in an equivalent of Instances[id].Type.
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Instances map[*ast.Ident]Instance
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// Defs maps identifiers to the objects they define (including
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// package names, dots "." of dot-imports, and blank "_" identifiers).
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// For identifiers that do not denote objects (e.g., the package name
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// in package clauses, or symbolic variables t in t := x.(type) of
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// type switch headers), the corresponding objects are nil.
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//
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// For an embedded field, Defs returns the field *Var it defines.
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//
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// Invariant: Defs[id] == nil || Defs[id].Pos() == id.Pos()
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Defs map[*ast.Ident]Object
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// Uses maps identifiers to the objects they denote.
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//
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// For an embedded field, Uses returns the *TypeName it denotes.
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//
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// Invariant: Uses[id].Pos() != id.Pos()
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Uses map[*ast.Ident]Object
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// Implicits maps nodes to their implicitly declared objects, if any.
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// The following node and object types may appear:
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//
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// node declared object
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//
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// *ast.ImportSpec *PkgName for imports without renames
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// *ast.CaseClause type-specific *Var for each type switch case clause (incl. default)
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// *ast.Field anonymous parameter *Var (incl. unnamed results)
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//
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Implicits map[ast.Node]Object
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// Selections maps selector expressions (excluding qualified identifiers)
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// to their corresponding selections.
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Selections map[*ast.SelectorExpr]*Selection
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// Scopes maps ast.Nodes to the scopes they define. Package scopes are not
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// associated with a specific node but with all files belonging to a package.
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// Thus, the package scope can be found in the type-checked Package object.
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// Scopes nest, with the Universe scope being the outermost scope, enclosing
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// the package scope, which contains (one or more) files scopes, which enclose
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// function scopes which in turn enclose statement and function literal scopes.
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// Note that even though package-level functions are declared in the package
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// scope, the function scopes are embedded in the file scope of the file
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// containing the function declaration.
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//
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// The Scope of a function contains the declarations of any
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// type parameters, parameters, and named results, plus any
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// local declarations in the body block.
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// It is coextensive with the complete extent of the
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// function's syntax ([*ast.FuncDecl] or [*ast.FuncLit]).
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// The Scopes mapping does not contain an entry for the
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// function body ([*ast.BlockStmt]); the function's scope is
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// associated with the [*ast.FuncType].
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//
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// The following node types may appear in Scopes:
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//
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// *ast.File
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// *ast.FuncType
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// *ast.TypeSpec
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// *ast.BlockStmt
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// *ast.IfStmt
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// *ast.SwitchStmt
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// *ast.TypeSwitchStmt
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// *ast.CaseClause
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// *ast.CommClause
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// *ast.ForStmt
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// *ast.RangeStmt
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//
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Scopes map[ast.Node]*Scope
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// InitOrder is the list of package-level initializers in the order in which
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// they must be executed. Initializers referring to variables related by an
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// initialization dependency appear in topological order, the others appear
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// in source order. Variables without an initialization expression do not
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// appear in this list.
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InitOrder []*Initializer
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// FileVersions maps a file to its Go version string.
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// If the file doesn't specify a version, the reported
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// string is Config.GoVersion.
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// Version strings begin with “go”, like “go1.21”, and
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// are suitable for use with the [go/version] package.
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FileVersions map[*ast.File]string
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}
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func (info *Info) recordTypes() bool {
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return info.Types != nil
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}
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// TypeOf returns the type of expression e, or nil if not found.
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// Precondition: the Types, Uses and Defs maps are populated.
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func (info *Info) TypeOf(e ast.Expr) Type {
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if t, ok := info.Types[e]; ok {
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return t.Type
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}
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if id, _ := e.(*ast.Ident); id != nil {
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if obj := info.ObjectOf(id); obj != nil {
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return obj.Type()
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}
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}
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return nil
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}
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// ObjectOf returns the object denoted by the specified id,
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// or nil if not found.
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//
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// If id is an embedded struct field, [Info.ObjectOf] returns the field (*[Var])
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// it defines, not the type (*[TypeName]) it uses.
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//
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// Precondition: the Uses and Defs maps are populated.
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func (info *Info) ObjectOf(id *ast.Ident) Object {
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if obj := info.Defs[id]; obj != nil {
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return obj
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}
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return info.Uses[id]
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}
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// PkgNameOf returns the local package name defined by the import,
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// or nil if not found.
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//
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// For dot-imports, the package name is ".".
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//
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// Precondition: the Defs and Implicts maps are populated.
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func (info *Info) PkgNameOf(imp *ast.ImportSpec) *PkgName {
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var obj Object
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if imp.Name != nil {
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obj = info.Defs[imp.Name]
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} else {
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obj = info.Implicits[imp]
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}
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pkgname, _ := obj.(*PkgName)
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return pkgname
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}
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// TypeAndValue reports the type and value (for constants)
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// of the corresponding expression.
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type TypeAndValue struct {
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mode operandMode
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Type Type
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Value constant.Value
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}
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// IsVoid reports whether the corresponding expression
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// is a function call without results.
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func (tv TypeAndValue) IsVoid() bool {
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return tv.mode == novalue
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}
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// IsType reports whether the corresponding expression specifies a type.
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func (tv TypeAndValue) IsType() bool {
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return tv.mode == typexpr
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}
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// IsBuiltin reports whether the corresponding expression denotes
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// a (possibly parenthesized) built-in function.
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func (tv TypeAndValue) IsBuiltin() bool {
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return tv.mode == builtin
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}
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// IsValue reports whether the corresponding expression is a value.
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// Builtins are not considered values. Constant values have a non-
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// nil Value.
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func (tv TypeAndValue) IsValue() bool {
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switch tv.mode {
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case constant_, variable, mapindex, value, commaok, commaerr:
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return true
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}
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return false
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}
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// IsNil reports whether the corresponding expression denotes the
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// predeclared value nil.
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func (tv TypeAndValue) IsNil() bool {
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return tv.mode == value && tv.Type == Typ[UntypedNil]
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}
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// Addressable reports whether the corresponding expression
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// is addressable (https://golang.org/ref/spec#Address_operators).
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func (tv TypeAndValue) Addressable() bool {
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return tv.mode == variable
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}
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// Assignable reports whether the corresponding expression
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// is assignable to (provided a value of the right type).
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func (tv TypeAndValue) Assignable() bool {
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return tv.mode == variable || tv.mode == mapindex
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}
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// HasOk reports whether the corresponding expression may be
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// used on the rhs of a comma-ok assignment.
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func (tv TypeAndValue) HasOk() bool {
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return tv.mode == commaok || tv.mode == mapindex
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}
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// Instance reports the type arguments and instantiated type for type and
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// function instantiations. For type instantiations, [Type] will be of dynamic
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// type *[Named]. For function instantiations, [Type] will be of dynamic type
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// *Signature.
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type Instance struct {
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TypeArgs *TypeList
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Type Type
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}
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// An Initializer describes a package-level variable, or a list of variables in case
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// of a multi-valued initialization expression, and the corresponding initialization
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// expression.
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type Initializer struct {
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Lhs []*Var // var Lhs = Rhs
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Rhs ast.Expr
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}
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func (init *Initializer) String() string {
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var buf bytes.Buffer
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for i, lhs := range init.Lhs {
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if i > 0 {
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buf.WriteString(", ")
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}
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buf.WriteString(lhs.Name())
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}
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buf.WriteString(" = ")
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WriteExpr(&buf, init.Rhs)
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return buf.String()
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}
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// Check type-checks a package and returns the resulting package object and
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// the first error if any. Additionally, if info != nil, Check populates each
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// of the non-nil maps in the [Info] struct.
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//
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// The package is marked as complete if no errors occurred, otherwise it is
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// incomplete. See [Config.Error] for controlling behavior in the presence of
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// errors.
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//
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// The package is specified by a list of *ast.Files and corresponding
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// file set, and the package path the package is identified with.
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// The clean path must not be empty or dot (".").
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func (conf *Config) Check(path string, fset *token.FileSet, files []*ast.File, info *Info) (*Package, error) {
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pkg := NewPackage(path, "")
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return pkg, NewChecker(conf, fset, pkg, info).Files(files)
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}
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