src

create.go (9215B)

---

 // Copyright 2013 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 ssa
 
 // This file implements the CREATE phase of SSA construction.
 // See builder.go for explanation.
 
 import (
 	"fmt"
 	"go/ast"
 	"go/token"
 	"go/types"
 	"os"
 	"sync"
 
 	"golang.org/x/tools/internal/versions"
 )
 
 // NewProgram returns a new SSA Program.
 //
 // mode controls diagnostics and checking during SSA construction.
 //
 // To construct an SSA program:
 //
 //   - Call NewProgram to create an empty Program.
 //   - Call CreatePackage providing typed syntax for each package
 //     you want to build, and call it with types but not
 //     syntax for each of those package's direct dependencies.
 //   - Call [Package.Build] on each syntax package you wish to build,
 //     or [Program.Build] to build all of them.
 //
 // See the Example tests for simple examples.
 func NewProgram(fset *token.FileSet, mode BuilderMode) *Program {
 	return &Program{
 		Fset:     fset,
 		imported: make(map[string]*Package),
 		packages: make(map[*types.Package]*Package),
 		mode:     mode,
 		canon:    newCanonizer(),
 		ctxt:     types.NewContext(),
 	}
 }
 
 // memberFromObject populates package pkg with a member for the
 // typechecker object obj.
 //
 // For objects from Go source code, syntax is the associated syntax
 // tree (for funcs and vars only) and goversion defines the
 // appropriate interpretation; they will be used during the build
 // phase.
 func memberFromObject(pkg *Package, obj types.Object, syntax ast.Node, goversion string) {
 	name := obj.Name()
 	switch obj := obj.(type) {
 	case *types.Builtin:
 		if pkg.Pkg != types.Unsafe {
 			panic("unexpected builtin object: " + obj.String())
 		}
 
 	case *types.TypeName:
 		if name != "_" {
 			pkg.Members[name] = &Type{
 				object: obj,
 				pkg:    pkg,
 			}
 		}
 
 	case *types.Const:
 		c := &NamedConst{
 			object: obj,
 			Value:  NewConst(obj.Val(), obj.Type()),
 			pkg:    pkg,
 		}
 		pkg.objects[obj] = c
 		if name != "_" {
 			pkg.Members[name] = c
 		}
 
 	case *types.Var:
 		g := &Global{
 			Pkg:    pkg,
 			name:   name,
 			object: obj,
 			typ:    types.NewPointer(obj.Type()), // address
 			pos:    obj.Pos(),
 		}
 		pkg.objects[obj] = g
 		if name != "_" {
 			pkg.Members[name] = g
 		}
 
 	case *types.Func:
 		sig := obj.Type().(*types.Signature)
 		if sig.Recv() == nil && name == "init" {
 			pkg.ninit++
 			name = fmt.Sprintf("init#%d", pkg.ninit)
 		}
 		fn := createFunction(pkg.Prog, obj, name, syntax, pkg.info, goversion)
 		fn.Pkg = pkg
 		pkg.created = append(pkg.created, fn)
 		pkg.objects[obj] = fn
 		if name != "_" && sig.Recv() == nil {
 			pkg.Members[name] = fn // package-level function
 		}
 
 	default: // (incl. *types.Package)
 		panic("unexpected Object type: " + obj.String())
 	}
 }
 
 // createFunction creates a function or method. It supports both
 // CreatePackage (with or without syntax) and the on-demand creation
 // of methods in non-created packages based on their types.Func.
 func createFunction(prog *Program, obj *types.Func, name string, syntax ast.Node, info *types.Info, goversion string) *Function {
 	sig := obj.Type().(*types.Signature)
 
 	/* declared function/method (from syntax or export data) */
 	fn := &Function{
 		name:           name,
 		object:         obj,
 		Signature:      sig,
 		build:          (*builder).buildFromSyntax,
 		syntax:         syntax,
 		info:           info,
 		goversion:      goversion,
 		pos:            obj.Pos(),
 		Pkg:            nil, // may be set by caller
 		Prog:           prog,
 		recvtypeparams: sig.RecvTypeParams(),
 		typeparams:     sig.TypeParams(),
 	}
 	if fn.syntax == nil {
 		fn.Synthetic = "from type information"
 		fn.build = (*builder).buildParamsOnly
 	}
 	if fn.hasTypeParams() {
 		fn.generic = new(generic)
 	}
 	return fn
 }
 
 // membersFromDecl populates package pkg with members for each
 // typechecker object (var, func, const or type) associated with the
 // specified decl.
 func membersFromDecl(pkg *Package, decl ast.Decl, goversion string) {
 	switch decl := decl.(type) {
 	case *ast.GenDecl: // import, const, type or var
 		switch decl.Tok {
 		case token.CONST:
 			for _, spec := range decl.Specs {
 				for _, id := range spec.(*ast.ValueSpec).Names {
 					memberFromObject(pkg, pkg.info.Defs[id], nil, "")
 				}
 			}
 
 		case token.VAR:
 			for _, spec := range decl.Specs {
 				for _, rhs := range spec.(*ast.ValueSpec).Values {
 					pkg.initVersion[rhs] = goversion
 				}
 				for _, id := range spec.(*ast.ValueSpec).Names {
 					memberFromObject(pkg, pkg.info.Defs[id], spec, goversion)
 				}
 			}
 
 		case token.TYPE:
 			for _, spec := range decl.Specs {
 				id := spec.(*ast.TypeSpec).Name
 				memberFromObject(pkg, pkg.info.Defs[id], nil, "")
 			}
 		}
 
 	case *ast.FuncDecl:
 		id := decl.Name
 		memberFromObject(pkg, pkg.info.Defs[id], decl, goversion)
 	}
 }
 
 // CreatePackage creates and returns an SSA Package from the
 // specified type-checked, error-free file ASTs, and populates its
 // Members mapping.
 //
 // importable determines whether this package should be returned by a
 // subsequent call to ImportedPackage(pkg.Path()).
 //
 // The real work of building SSA form for each function is not done
 // until a subsequent call to Package.Build.
 func (prog *Program) CreatePackage(pkg *types.Package, files []*ast.File, info *types.Info, importable bool) *Package {
 	if pkg == nil {
 		panic("nil pkg") // otherwise pkg.Scope below returns types.Universe!
 	}
 	p := &Package{
 		Prog:    prog,
 		Members: make(map[string]Member),
 		objects: make(map[types.Object]Member),
 		Pkg:     pkg,
 		syntax:  info != nil,
 		// transient values (cleared after Package.Build)
 		info:        info,
 		files:       files,
 		initVersion: make(map[ast.Expr]string),
 	}
 
 	/* synthesized package initializer */
 	p.init = &Function{
 		name:      "init",
 		Signature: new(types.Signature),
 		Synthetic: "package initializer",
 		Pkg:       p,
 		Prog:      prog,
 		build:     (*builder).buildPackageInit,
 		info:      p.info,
 		goversion: "", // See Package.build for details.
 	}
 	p.Members[p.init.name] = p.init
 	p.created = append(p.created, p.init)
 
 	// Allocate all package members: vars, funcs, consts and types.
 	if len(files) > 0 {
 		// Go source package.
 		for _, file := range files {
 			goversion := versions.Lang(versions.FileVersion(p.info, file))
 			for _, decl := range file.Decls {
 				membersFromDecl(p, decl, goversion)
 			}
 		}
 	} else {
 		// GC-compiled binary package (or "unsafe")
 		// No code.
 		// No position information.
 		scope := p.Pkg.Scope()
 		for _, name := range scope.Names() {
 			obj := scope.Lookup(name)
 			memberFromObject(p, obj, nil, "")
 			if obj, ok := obj.(*types.TypeName); ok {
 				// No Unalias: aliases should not duplicate methods.
 				if named, ok := obj.Type().(*types.Named); ok {
 					for i, n := 0, named.NumMethods(); i < n; i++ {
 						memberFromObject(p, named.Method(i), nil, "")
 					}
 				}
 			}
 		}
 	}
 
 	if prog.mode&BareInits == 0 {
 		// Add initializer guard variable.
 		initguard := &Global{
 			Pkg:  p,
 			name: "init$guard",
 			typ:  types.NewPointer(tBool),
 		}
 		p.Members[initguard.Name()] = initguard
 	}
 
 	if prog.mode&GlobalDebug != 0 {
 		p.SetDebugMode(true)
 	}
 
 	if prog.mode&PrintPackages != 0 {
 		printMu.Lock()
 		p.WriteTo(os.Stdout)
 		printMu.Unlock()
 	}
 
 	if importable {
 		prog.imported[p.Pkg.Path()] = p
 	}
 	prog.packages[p.Pkg] = p
 
 	return p
 }
 
 // printMu serializes printing of Packages/Functions to stdout.
 var printMu sync.Mutex
 
 // AllPackages returns a new slice containing all packages created by
 // prog.CreatePackage in unspecified order.
 func (prog *Program) AllPackages() []*Package {
 	pkgs := make([]*Package, 0, len(prog.packages))
 	for _, pkg := range prog.packages {
 		pkgs = append(pkgs, pkg)
 	}
 	return pkgs
 }
 
 // ImportedPackage returns the importable Package whose PkgPath
 // is path, or nil if no such Package has been created.
 //
 // A parameter to CreatePackage determines whether a package should be
 // considered importable. For example, no import declaration can resolve
 // to the ad-hoc main package created by 'go build foo.go'.
 //
 // TODO(adonovan): rethink this function and the "importable" concept;
 // most packages are importable. This function assumes that all
 // types.Package.Path values are unique within the ssa.Program, which is
 // false---yet this function remains very convenient.
 // Clients should use (*Program).Package instead where possible.
 // SSA doesn't really need a string-keyed map of packages.
 //
 // Furthermore, the graph of packages may contain multiple variants
 // (e.g. "p" vs "p as compiled for q.test"), and each has a different
 // view of its dependencies.
 func (prog *Program) ImportedPackage(path string) *Package {
 	return prog.imported[path]
 }
 
 // SetNoReturn sets the predicate used when building the ssa.Program
 // prog that reports whether a given function cannot return.
 // This may be used to prune spurious control flow edges
 // after (e.g.) log.Fatal, improving the precision of analyses.
 //
 // A typical implementation is the [ctrlflow.CFGs.NoReturn] method from
 // [golang.org/x/tools/go/analysis/passes/ctrlflow].
 func (prog *Program) SetNoReturn(noReturn func(*types.Func) bool) {
 	prog.noReturn = noReturn
 }