go/go/types/resolve.go

// 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 types

import (
	"fmt"
	"go/ast"
	"go/token"
	"strconv"
)

func (check *checker) declareObj(scope, altScope *Scope, obj Object, dotImport token.Pos) {
	alt := scope.Insert(obj)
	if alt == nil && altScope != nil {
		// see if there is a conflicting declaration in altScope
		alt = altScope.Lookup(obj.Name())
	}
	if alt != nil {
		prevDecl := ""

		// for dot-imports, local declarations are declared first - swap messages
		if dotImport.IsValid() {
			if pos := alt.Pos(); pos.IsValid() {
				check.errorf(pos, fmt.Sprintf("%s redeclared in this block by import at %s",
					obj.Name(), check.fset.Position(dotImport)))
				return
			}

			// get by w/o other position
			check.errorf(dotImport, fmt.Sprintf("dot-import redeclares %s", obj.Name()))
			return
		}

		if pos := alt.Pos(); pos.IsValid() {
			prevDecl = fmt.Sprintf("\n\tother declaration at %s", check.fset.Position(pos))
		}
		check.errorf(obj.Pos(), fmt.Sprintf("%s redeclared in this block%s", obj.Name(), prevDecl))
	}
}

func (check *checker) resolveIdent(scope *Scope, ident *ast.Ident) bool {
	for ; scope != nil; scope = scope.Outer {
		if obj := scope.Lookup(ident.Name); obj != nil {
			check.register(ident, obj)
			return true
		}
	}
	return false
}

func (check *checker) resolve(importer Importer, files []*ast.File) (methods []*ast.FuncDecl) {
	pkg := check.pkg

	// complete package scope
	for _, file := range files {
		// the package identifier denotes the current package
		check.register(file.Name, pkg)

		// insert top-level file objects in package scope
		// (the parser took care of declaration errors in a single file,
		// but not across multiple files - hence we need to check again)
		for _, decl := range file.Decls {
			switch d := decl.(type) {
			case *ast.BadDecl:
				// ignore
			case *ast.GenDecl:
				if d.Tok == token.CONST {
					check.assocInitvals(d)
				}
				for _, spec := range d.Specs {
					switch s := spec.(type) {
					case *ast.ImportSpec:
						// handled separately below
					case *ast.ValueSpec:
						for _, name := range s.Names {
							if name.Name == "_" {
								continue
							}
							check.declareObj(pkg.scope, nil, check.lookup(name), token.NoPos)
						}
					case *ast.TypeSpec:
						if s.Name.Name == "_" {
							continue
						}
						check.declareObj(pkg.scope, nil, check.lookup(s.Name), token.NoPos)
					default:
						check.invalidAST(s.Pos(), "unknown ast.Spec node %T", s)
					}
				}
			case *ast.FuncDecl:
				if d.Recv != nil {
					// collect method
					methods = append(methods, d)
					continue
				}
				if d.Name.Name == "_" || d.Name.Name == "init" {
					continue // blank (_) and init functions are inaccessible
				}
				check.declareObj(pkg.scope, nil, check.lookup(d.Name), token.NoPos)
			default:
				check.invalidAST(d.Pos(), "unknown ast.Decl node %T", d)
			}
		}
	}

	// complete file scopes with imports and resolve identifiers
	for _, file := range files {
		// build file scope by processing all imports
		importErrors := false
		fileScope := &Scope{Outer: pkg.scope}
		for _, spec := range file.Imports {
			if importer == nil {
				importErrors = true
				continue
			}
			path, _ := strconv.Unquote(spec.Path.Value)
			imp, err := importer(pkg.imports, path)
			if err != nil {
				check.errorf(spec.Path.Pos(), "could not import %s (%s)", path, err)
				importErrors = true
				continue
			}
			// TODO(gri) If a local package name != "." is provided,
			// global identifier resolution could proceed even if the
			// import failed. Consider adjusting the logic here a bit.

			// local name overrides imported package name
			name := imp.name
			if spec.Name != nil {
				name = spec.Name.Name
			}

			// add import to file scope
			if name == "." {
				// merge imported scope with file scope
				for _, obj := range imp.scope.Entries {
					// gcimported package scopes contain non-exported
					// objects such as types used in partially exported
					// objects - do not accept them
					if ast.IsExported(obj.Name()) {
						check.declareObj(fileScope, pkg.scope, obj, spec.Pos())
					}
				}
				// TODO(gri) consider registering the "." identifier
				// if we have Context.Ident callbacks for say blank
				// (_) identifiers
				// check.register(spec.Name, pkg)
			} else if name != "_" {
				// declare imported package object in file scope
				// (do not re-use imp in the file scope but create
				// a new object instead; the Decl field is different
				// for different files)
				obj := &Package{name: name, scope: imp.scope, spec: spec}
				check.declareObj(fileScope, pkg.scope, obj, token.NoPos)
			}
		}

		// resolve identifiers
		if importErrors {
			// don't use the universe scope without correct imports
			// (objects in the universe may be shadowed by imports;
			// with missing imports, identifiers might get resolved
			// incorrectly to universe objects)
			pkg.scope.Outer = nil
		}
		i := 0
		for _, ident := range file.Unresolved {
			if !check.resolveIdent(fileScope, ident) {
				check.errorf(ident.Pos(), "undeclared name: %s", ident.Name)
				file.Unresolved[i] = ident
				i++
			}

		}
		file.Unresolved = file.Unresolved[0:i]
		pkg.scope.Outer = Universe // reset outer scope (is nil if there were importErrors)
	}

	return
}