go.tools/go/loader: use new types.TypeAndValue mode predicates.

PackageInfo:
- deleted IsType
- inlined + deleted: ValueOf, TypeCaseVar, ImportSpecPkg
- on failure, TypeOf accessor now returns nil (was: panic)

go/ssa: avoid extra map lookups by using Uses or Defs directly when safe to do so,
and keeping the TypeAndValue around in expr0().

LGTM=gri
R=gri, pcc
CC=golang-codereviews
https://golang.org/cl/107650043

3 files changed, 20 insertions, 17 deletions

diff --git a/oracle/callees.go b/oracle/callees.go
index a900b7b..8584403 100644
--- a/oracle/callees.go
+++ b/oracle/callees.go
@@ -38,13 +38,13 @@ func callees(o *Oracle, qpos *QueryPos) (queryResult, error) {
 	// not what the user intended.
 
 	// Reject type conversions.
-	if qpos.info.IsType(e.Fun) {
+	if qpos.info.Types[e.Fun].IsType() {
 		return nil, fmt.Errorf("this is a type conversion, not a function call")
 	}
 
 	// Reject calls to built-ins.
 	if id, ok := unparen(e.Fun).(*ast.Ident); ok {
-		if b, ok := qpos.info.ObjectOf(id).(*types.Builtin); ok {
+		if b, ok := qpos.info.Uses[id].(*types.Builtin); ok {
 			return nil, fmt.Errorf("this is a call to the built-in '%s' operator", b.Name())
 		}
 	}
diff --git a/oracle/describe.go b/oracle/describe.go
index 149172c..26a81b9 100644
--- a/oracle/describe.go
+++ b/oracle/describe.go
@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"go/ast"
 	"go/token"
+	"log"
 	"os"
 	"strings"
 
@@ -180,7 +181,8 @@ func findInterestingNode(pkginfo *loader.PackageInfo, path []ast.Node) ([]ast.No
 			return path, actionExpr
 
 		case *ast.SelectorExpr:
-			if pkginfo.ObjectOf(n.Sel) == nil {
+			// TODO(adonovan): use Selections info directly.
+			if pkginfo.Uses[n.Sel] == nil {
 				// TODO(adonovan): is this reachable?
 				return path, actionUnknown
 			}
@@ -267,15 +269,15 @@ func findInterestingNode(pkginfo *loader.PackageInfo, path []ast.Node) ([]ast.No
 				return path[1:], actionPackage
 
 			default:
-				// e.g. blank identifier (go/types bug?)
-				// or y in "switch y := x.(type)" (go/types bug?)
+				// e.g. blank identifier
+				// or y in "switch y := x.(type)"
 				// or code in a _test.go file that's not part of the package.
-				fmt.Printf("unknown reference %s in %T\n", n, path[1])
+				log.Printf("unknown reference %s in %T\n", n, path[1])
 				return path, actionUnknown
 			}
 
 		case *ast.StarExpr:
-			if pkginfo.IsType(n) {
+			if pkginfo.Types[n].IsType() {
 				return path, actionType
 			}
 			return path, actionExpr
@@ -311,7 +313,7 @@ func describeValue(o *Oracle, qpos *QueryPos, path []ast.Node) (*describeValueRe
 	}
 
 	typ := qpos.info.TypeOf(expr)
-	constVal := qpos.info.ValueOf(expr)
+	constVal := qpos.info.Types[expr].Value
 
 	return &describeValueResult{
 		qpos:     qpos,
@@ -497,7 +499,12 @@ func describePackage(o *Oracle, qpos *QueryPos, path []ast.Node) (*describePacka
 	var pkg *types.Package
 	switch n := path[0].(type) {
 	case *ast.ImportSpec:
-		pkgname := qpos.info.ImportSpecPkg(n)
+		var pkgname *types.PkgName
+		if n.Name != nil {
+			pkgname = qpos.info.Defs[n.Name].(*types.PkgName)
+		} else if p := qpos.info.Implicits[n]; p != nil {
+			pkgname = p.(*types.PkgName)
+		}
 		description = fmt.Sprintf("import of package %q", pkgname.Pkg().Path())
 		pkg = pkgname.Pkg()
 
@@ -507,7 +514,7 @@ func describePackage(o *Oracle, qpos *QueryPos, path []ast.Node) (*describePacka
 			pkg = qpos.info.Pkg
 			description = fmt.Sprintf("definition of package %q", pkg.Path())
 		} else {
-			// e.g. import id
+			// e.g. import id "..."
 			//  or  id.F()
 			pkg = qpos.info.ObjectOf(n).Pkg()
 			description = fmt.Sprintf("reference to package %q", pkg.Path())
@@ -662,7 +669,7 @@ func describeStmt(o *Oracle, qpos *QueryPos, path []ast.Node) (*describeStmtResu
 	var description string
 	switch n := path[0].(type) {
 	case *ast.Ident:
-		if qpos.info.ObjectOf(n).Pos() == n.Pos() {
+		if qpos.info.Defs[n] != nil {
 			description = "labelled statement"
 		} else {
 			description = "reference to labelled statement"
diff --git a/oracle/freevars.go b/oracle/freevars.go
index a142d15..5582318 100644
--- a/oracle/freevars.go
+++ b/oracle/freevars.go
@@ -51,17 +51,13 @@ func freevars(o *Oracle, qpos *QueryPos) (queryResult, error) {
 	}
 
 	id = func(n *ast.Ident) types.Object {
-		obj := qpos.info.ObjectOf(n)
+		obj := qpos.info.Uses[n]
 		if obj == nil {
-			return nil // TODO(adonovan): fix: this fails for *types.Label.
-			panic("no types.Object for ast.Ident")
+			return nil // not a reference
 		}
 		if _, ok := obj.(*types.PkgName); ok {
 			return nil // imported package
 		}
-		if n.Pos() == obj.Pos() {
-			return nil // this ident is the definition, not a reference
-		}
 		if !(file.Pos() <= obj.Pos() && obj.Pos() <= file.End()) {
 			return nil // not defined in this file
 		}