exp/types: completed typechecking of parameter passing

Details:
- fixed variadic parameter passing and calls of the form f(g())
- fixed implementation of ^x for unsigned constants x
- fixed assignability of untyped booleans
- resolved a few TODOs, various minor fixes
- enabled many more tests (only 6 std packages don't typecheck)

R=rsc
CC=golang-dev
https://golang.org/cl/6930053

src/pkg/exp/gotype/gotype_test.go

@@ -50,7 +50,7 @@ var tests = []string{
 
 	// directories
 	// Note: packages that don't typecheck yet are commented out
-	// "archive/tar", // investigate
+	"archive/tar",
 	"archive/zip",
 
 	"bufio",
@@ -77,13 +77,13 @@ var tests = []string{
 	"crypto/md5",
 	"crypto/rand",
 	"crypto/rc4",
-	// "crypto/rsa", // investigate (GOARCH=386)
+	// "crypto/rsa", // src/pkg/crypto/rsa/pkcs1v15.go:21:27: undeclared name: io
 	"crypto/sha1",
 	"crypto/sha256",
 	"crypto/sha512",
 	"crypto/subtle",
 	"crypto/tls",
-	// "crypto/x509", // investigate
+	// "crypto/x509", // src/pkg/crypto/x509/root.go:15:10: undeclared name: initSystemRoots
 	"crypto/x509/pkix",
 
 	"database/sql",
@@ -117,7 +117,7 @@ var tests = []string{
 
 	"go/ast",
 	"go/build",
-	// "go/doc", // variadic parameters don't work yet fully
+	"go/doc",
 	"go/format",
 	"go/parser",
 	"go/printer",
@@ -125,7 +125,7 @@ var tests = []string{
 	"go/token",
 
 	"hash/adler32",
-	// "hash/crc32", // investigate
+	"hash/crc32",
 	"hash/crc64",
 	"hash/fnv",
 
@@ -139,54 +139,54 @@ var tests = []string{
 	"index/suffixarray",
 
 	"io",
-	// "io/ioutil", // investigate
+	"io/ioutil",
 
 	"log",
 	"log/syslog",
 
 	"math",
-	// "math/big", // investigate
+	"math/big",
 	"math/cmplx",
 	"math/rand",
 
 	"mime",
 	"mime/multipart",
 
-	// "net", // depends on C files
+	// "net", // src/pkg/net/lookup_unix.go:56:20: undeclared name: cgoLookupHost
 	"net/http",
 	"net/http/cgi",
-	// "net/http/fcgi", // investigate
+	"net/http/fcgi",
 	"net/http/httptest",
 	"net/http/httputil",
-	// "net/http/pprof", // investigate
+	"net/http/pprof",
 	"net/mail",
-	// "net/rpc", // investigate
+	"net/rpc",
 	"net/rpc/jsonrpc",
 	"net/smtp",
 	"net/textproto",
 	"net/url",
 
-	// "path", // variadic parameters don't work yet fully
-	// "path/filepath", // investigate
+	"path",
+	"path/filepath",
 
-	// "reflect", // investigate
+	// "reflect", // unsafe.Sizeof must return size > 0 for pointer types
 
 	"regexp",
 	"regexp/syntax",
 
 	"runtime",
-	// "runtime/cgo", // import "C"
+	"runtime/cgo",
 	"runtime/debug",
 	"runtime/pprof",
 
 	"sort",
-	// "strconv", // investigate
+	// "strconv", // bug in switch case duplicate detection
 	"strings",
 
-	// "sync", // platform-specific files
-	// "sync/atomic", // platform-specific files
+	"sync",
+	"sync/atomic",
 
-	// "syscall", // platform-specific files
+	"syscall",
 
 	"testing",
 	"testing/iotest",
@@ -194,10 +194,10 @@ var tests = []string{
 
 	"text/scanner",
 	"text/tabwriter",
-	// "text/template", // variadic parameters don't work yet fully
-	// "text/template/parse", // variadic parameters don't work yet fully
+	"text/template",
+	"text/template/parse",
 
-	// "time", // platform-specific files
+	// "time", // local const decls without initialization expressions
 	"unicode",
 	"unicode/utf16",
 	"unicode/utf8",

src/pkg/exp/types/builtins.go

@@ -155,13 +155,14 @@ func (check *checker) builtin(x *operand, call *ast.CallExpr, bin *builtin, iota
 			goto Error
 		}
 
+		typ := underlying(x.typ).(*Basic)
 		if x.mode == constant && y.mode == constant {
-			x.val = binaryOpConst(x.val, toImagConst(y.val), token.ADD, false)
+			x.val = binaryOpConst(x.val, toImagConst(y.val), token.ADD, typ)
 		} else {
 			x.mode = value
 		}
 
-		switch underlying(x.typ).(*Basic).Kind {
+		switch typ.Kind {
 		case Float32:
 			x.typ = Typ[Complex64]
 		case Float64:

src/pkg/exp/types/const.go

@@ -49,12 +49,17 @@ func (nilType) String() string {
 	return "nil"
 }
 
-// Frequently used constants.
+// Implementation-specific constants.
+// TODO(gri) These need to go elsewhere.
+const (
+	intBits = 32
+	ptrBits = 64
+)
+
+// Frequently used values.
 var (
-	zeroConst     = int64(0)
-	oneConst      = int64(1)
-	minusOneConst = int64(-1)
-	nilConst      = nilType{}
+	nilConst  = nilType{}
+	zeroConst = int64(0)
 )
 
 // int64 bounds
@@ -74,7 +79,7 @@ func normalizeIntConst(x *big.Int) interface{} {
 }
 
 // normalizeRatConst returns the smallest constant representation
-// for the specific value of x; either an int64, *big.Int value,
+// for the specific value of x; either an int64, *big.Int,
 // or *big.Rat value.
 //
 func normalizeRatConst(x *big.Rat) interface{} {
@@ -84,15 +89,15 @@ func normalizeRatConst(x *big.Rat) interface{} {
 	return x
 }
 
-// normalizeComplexConst returns the smallest constant representation
-// for the specific value of x; either an int64, *big.Int value, *big.Rat,
-// or complex value.
+// newComplex returns the smallest constant representation
+// for the specific value re + im*i; either an int64, *big.Int,
+// *big.Rat, or complex value.
 //
-func normalizeComplexConst(x complex) interface{} {
-	if x.im.Sign() == 0 {
-		return normalizeRatConst(x.re)
+func newComplex(re, im *big.Rat) interface{} {
+	if im.Sign() == 0 {
+		return normalizeRatConst(re)
 	}
-	return x
+	return complex{re, im}
 }
 
 // makeRuneConst returns the int64 code point for the rune literal
@@ -140,7 +145,7 @@ func makeComplexConst(lit string) interface{} {
 	n := len(lit)
 	if n > 0 && lit[n-1] == 'i' {
 		if im, ok := new(big.Rat).SetString(lit[0 : n-1]); ok {
-			return normalizeComplexConst(complex{big.NewRat(0, 1), im})
+			return newComplex(big.NewRat(0, 1), im)
 		}
 	}
 	return nil
@@ -202,9 +207,6 @@ func isNegConst(x interface{}) bool {
 // of precision.
 //
 func isRepresentableConst(x interface{}, as BasicKind) bool {
-	const intBits = 32 // TODO(gri) implementation-specific constant
-	const ptrBits = 64 // TODO(gri) implementation-specific constant
-
 	switch x := x.(type) {
 	case bool:
 		return as == Bool || as == UntypedBool
@@ -386,13 +388,71 @@ func is63bit(x int64) bool {
 	return -1<<62 <= x && x <= 1<<62-1
 }
 
+// unaryOpConst returns the result of the constant evaluation op x where x is of the given type.
+func unaryOpConst(x interface{}, op token.Token, typ *Basic) interface{} {
+	switch op {
+	case token.ADD:
+		return x // nothing to do
+	case token.SUB:
+		switch x := x.(type) {
+		case int64:
+			if z := -x; z != x {
+				return z // no overflow
+			}
+			// overflow - need to convert to big.Int
+			return normalizeIntConst(new(big.Int).Neg(big.NewInt(x)))
+		case *big.Int:
+			return normalizeIntConst(new(big.Int).Neg(x))
+		case *big.Rat:
+			return normalizeRatConst(new(big.Rat).Neg(x))
+		case complex:
+			return newComplex(new(big.Rat).Neg(x.re), new(big.Rat).Neg(x.im))
+		}
+	case token.XOR:
+		var z big.Int
+		switch x := x.(type) {
+		case int64:
+			z.Not(big.NewInt(x))
+		case *big.Int:
+			z.Not(x)
+		default:
+			unreachable()
+		}
+		// For unsigned types, the result will be negative and
+		// thus "too large": We must limit the result size to
+		// the type's size.
+		if typ.Info&IsUnsigned != 0 {
+			s := uint(typ.Size) * 8
+			if s == 0 {
+				// platform-specific type
+				// TODO(gri) this needs to be factored out
+				switch typ.Kind {
+				case Uint:
+					s = intBits
+				case Uintptr:
+					s = ptrBits
+				default:
+					unreachable()
+				}
+			}
+			// z &^= (-1)<<s
+			z.AndNot(&z, new(big.Int).Lsh(big.NewInt(-1), s))
+		}
+		return normalizeIntConst(&z)
+	case token.NOT:
+		return !x.(bool)
+	}
+	unreachable()
+	return nil
+}
+
 // binaryOpConst returns the result of the constant evaluation x op y;
-// both operands must be of the same "kind" (boolean, numeric, or string).
-// If intDiv is true, division (op == token.QUO) is using integer division
+// both operands must be of the same constant "kind" (boolean, numeric, or string).
+// If typ is an integer type, division (op == token.QUO) is using integer division
 // (and the result is guaranteed to be integer) rather than floating-point
 // division. Division by zero leads to a run-time panic.
 //
-func binaryOpConst(x, y interface{}, op token.Token, intDiv bool) interface{} {
+func binaryOpConst(x, y interface{}, op token.Token, typ *Basic) interface{} {
 	x, y = matchConst(x, y)
 
 	switch x := x.(type) {
@@ -403,8 +463,6 @@ func binaryOpConst(x, y interface{}, op token.Token, intDiv bool) interface{} {
 			return x && y
 		case token.LOR:
 			return x || y
-		default:
-			unreachable()
 		}
 
 	case int64:
@@ -431,7 +489,7 @@ func binaryOpConst(x, y interface{}, op token.Token, intDiv bool) interface{} {
 		case token.REM:
 			return x % y
 		case token.QUO:
-			if intDiv {
+			if typ.Info&IsInteger != 0 {
 				return x / y
 			}
 			return normalizeRatConst(new(big.Rat).SetFrac(big.NewInt(x), big.NewInt(y)))
@@ -443,8 +501,6 @@ func binaryOpConst(x, y interface{}, op token.Token, intDiv bool) interface{} {
 			return x ^ y
 		case token.AND_NOT:
 			return x &^ y
-		default:
-			unreachable()
 		}
 
 	case *big.Int:
@@ -460,7 +516,7 @@ func binaryOpConst(x, y interface{}, op token.Token, intDiv bool) interface{} {
 		case token.REM:
 			z.Rem(x, y)
 		case token.QUO:
-			if intDiv {
+			if typ.Info&IsInteger != 0 {
 				z.Quo(x, y)
 			} else {
 				return normalizeRatConst(new(big.Rat).SetFrac(x, y))
@@ -533,7 +589,7 @@ func binaryOpConst(x, y interface{}, op token.Token, intDiv bool) interface{} {
 		default:
 			unreachable()
 		}
-		return normalizeComplexConst(complex{&re, &im})
+		return newComplex(&re, &im)
 
 	case string:
 		if op == token.ADD {

src/pkg/exp/types/errors.go

@@ -266,15 +266,8 @@ func writeType(buf *bytes.Buffer, typ Type) {
 		buf.WriteByte('*')
 		writeType(buf, t.Base)
 
-	case *tuple:
-		buf.WriteByte('(')
-		for i, typ := range t.list {
-			if i > 0 {
-				buf.WriteString("; ")
-			}
-			writeType(buf, typ)
-		}
-		buf.WriteByte(')')
+	case *Result:
+		writeParams(buf, t.Values, false)
 
 	case *Signature:
 		buf.WriteString("func")

src/pkg/exp/types/expr.go

@@ -19,7 +19,6 @@ import (
 // - at the moment, iota is passed around almost everywhere - in many places we know it cannot be used
 
 // TODO(gri) API issues
-// - clients need access to result type information (tuples)
 // - clients need access to constant values
 // - clients need access to built-in type information
 
@@ -212,21 +211,11 @@ func (check *checker) unary(x *operand, op token.Token) {
 	}
 
 	if x.mode == constant {
-		switch op {
-		case token.ADD:
-			// nothing to do
-		case token.SUB:
-			x.val = binaryOpConst(zeroConst, x.val, token.SUB, false)
-		case token.XOR:
-			x.val = binaryOpConst(minusOneConst, x.val, token.XOR, false)
-		case token.NOT:
-			x.val = !x.val.(bool)
-		default:
-			unreachable() // operators where checked by check.op
-		}
+		typ := underlying(x.typ).(*Basic)
+		x.val = unaryOpConst(x.val, op, typ)
 		// Typed constants must be representable in
 		// their type after each constant operation.
-		check.isRepresentable(x, underlying(x.typ).(*Basic))
+		check.isRepresentable(x, typ)
 		return
 	}
 
@@ -304,6 +293,8 @@ func (check *checker) convertUntyped(x *operand, target Type) {
 		if !x.isNil() {
 			goto Error
 		}
+	default:
+		unreachable()
 	}
 
 	x.typ = target
@@ -332,7 +323,7 @@ func (check *checker) comparison(x, y *operand, op token.Token) {
 	}
 
 	if !valid {
-		check.invalidOp(x.pos(), "cannot compare %s and %s", x, y)
+		check.invalidOp(x.pos(), "cannot compare %s %s %s", x, op, y)
 		x.mode = invalid
 		return
 	}
@@ -465,10 +456,11 @@ func (check *checker) binary(x, y *operand, op token.Token, hint Type) {
 	}
 
 	if x.mode == constant && y.mode == constant {
-		x.val = binaryOpConst(x.val, y.val, op, isInteger(x.typ))
+		typ := underlying(x.typ).(*Basic)
+		x.val = binaryOpConst(x.val, y.val, op, typ)
 		// Typed constants must be representable in
 		// their type after each constant operation.
-		check.isRepresentable(x, underlying(x.typ).(*Basic))
+		check.isRepresentable(x, typ)
 		return
 	}
 
@@ -554,9 +546,15 @@ func (check *checker) indexedElts(elts []ast.Expr, typ Type, length int64, iota
 	return max
 }
 
-func (check *checker) argument(sig *Signature, i int, arg ast.Expr) {
+// argument typechecks passing an argument arg (if arg != nil) or
+// x (if arg == nil) to the i'th parameter of the given signature.
+// If passSlice is set, the argument is followed by ... in the call.
+//
+func (check *checker) argument(sig *Signature, i int, arg ast.Expr, x *operand, passSlice bool) {
+	// determine parameter
 	var par *ast.Object
-	if n := len(sig.Params); i < n {
+	n := len(sig.Params)
+	if i < n {
 		par = sig.Params[i]
 	} else if sig.IsVariadic {
 		par = sig.Params[n-1]
@@ -565,16 +563,32 @@ func (check *checker) argument(sig *Signature, i int, arg ast.Expr) {
 		return
 	}
 
-	// TODO(gri) deal with ... last argument
-	var z, x operand
+	// determine argument
+	var z operand
 	z.mode = variable
-	z.expr = nil            // TODO(gri) can we do better here?
-	z.typ = par.Type.(Type) // TODO(gri) should become something like checkObj(&z, ...) eventually
-	check.expr(&x, arg, z.typ, -1)
+	z.expr = nil // TODO(gri) can we do better here? (for good error messages)
+	z.typ = par.Type.(Type)
+
+	if arg != nil {
+		check.expr(x, arg, z.typ, -1)
+	}
 	if x.mode == invalid {
 		return // ignore this argument
 	}
-	check.assignOperand(&z, &x)
+
+	// check last argument of the form x...
+	if passSlice {
+		if i+1 != n {
+			check.errorf(x.pos(), "can only use ... with matching parameter")
+			return // ignore this argument
+		}
+		// spec: "If the final argument is assignable to a slice type []T,
+		// it may be passed unchanged as the value for a ...T parameter if
+		// the argument is followed by ..."
+		z.typ = &Slice{Elt: z.typ} // change final parameter type to []T
+	}
+
+	check.assignOperand(&z, x)
 }
 
 func (check *checker) recordType(x *operand) {
@@ -1052,25 +1066,79 @@ func (check *checker) rawExpr(x *operand, e ast.Expr, hint Type, iota int, cycle
 			check.conversion(x, e, x.typ, iota)
 		} else if sig, ok := underlying(x.typ).(*Signature); ok {
 			// check parameters
-			// TODO(gri)
-			// - deal with single multi-valued function arguments: f(g())
-			// - variadic functions only partially addressed
-			for i, arg := range e.Args {
-				check.argument(sig, i, arg)
+
+			// If we have a trailing ... at the end of the parameter
+			// list, the last argument must match the parameter type
+			// []T of a variadic function parameter x ...T.
+			passSlice := false
+			if e.Ellipsis.IsValid() {
+				if sig.IsVariadic {
+					passSlice = true
+				} else {
+					check.errorf(e.Ellipsis, "cannot use ... in call to %s", e.Fun)
+					// ok to continue
+				}
 			}
 
-			// determine result
-			x.mode = value
-			if len(sig.Results) == 1 {
-				x.typ = sig.Results[0].Type.(Type)
+			// If we have a single argument that is a function call
+			// we need to handle it separately. Determine if this
+			// is the case without checking the argument.
+			var call *ast.CallExpr
+			if len(e.Args) == 1 {
+				call, _ = unparen(e.Args[0]).(*ast.CallExpr)
+			}
+
+			n := 0 // parameter count
+			if call != nil {
+				// We have a single argument that is a function call.
+				check.expr(x, call, nil, -1)
+				if x.mode == invalid {
+					goto Error // TODO(gri): we can do better
+				}
+				if t, _ := x.typ.(*Result); t != nil {
+					// multiple result values
+					n = len(t.Values)
+					for i, obj := range t.Values {
+						x.mode = value
+						x.expr = nil // TODO(gri) can we do better here? (for good error messages)
+						x.typ = obj.Type.(Type)
+						check.argument(sig, i, nil, x, passSlice && i+1 == n)
+					}
+				} else {
+					// single result value
+					n = 1
+					check.argument(sig, 0, nil, x, passSlice)
+				}
+
 			} else {
-				// TODO(gri) change Signature representation to use tuples,
-				//           then this conversion is not required
-				list := make([]Type, len(sig.Results))
-				for i, obj := range sig.Results {
-					list[i] = obj.Type.(Type)
+				// We don't have a single argument or it is not a function call.
+				n = len(e.Args)
+				for i, arg := range e.Args {
+					check.argument(sig, i, arg, x, passSlice && i+1 == n)
 				}
-				x.typ = &tuple{list: list}
+			}
+
+			// determine if we have enough arguments
+			if sig.IsVariadic {
+				// a variadic function accepts an "empty"
+				// last argument: count one extra
+				n++
+			}
+			if n < len(sig.Params) {
+				check.errorf(e.Fun.Pos(), "too few arguments in call to %s", e.Fun)
+				// ok to continue
+			}
+
+			// determine result
+			switch len(sig.Results) {
+			case 0:
+				x.mode = novalue
+			case 1:
+				x.mode = value
+				x.typ = sig.Results[0].Type.(Type)
+			default:
+				x.mode = value
+				x.typ = &Result{Values: sig.Results}
 			}
 
 		} else if bin, ok := x.typ.(*builtin); ok {

src/pkg/exp/types/operand.go

@@ -182,7 +182,14 @@ func (x *operand) isAssignable(T Type) bool {
 	if isUntyped(Vu) {
 		switch t := Tu.(type) {
 		case *Basic:
-			return x.mode == constant && isRepresentableConst(x.val, t.Kind)
+			if x.mode == constant {
+				return isRepresentableConst(x.val, t.Kind)
+			}
+			// The result of a comparison is an untyped boolean,
+			// but may not be a constant.
+			if Vb, _ := Vu.(*Basic); Vb != nil {
+				return Vb.Kind == UntypedBool && isBoolean(Tu)
+			}
 		case *Interface:
 			return x.isNil() || len(t.Methods) == 0
 		case *Pointer, *Signature, *Slice, *Map, *Chan:

src/pkg/exp/types/predicates.go

@@ -225,25 +225,28 @@ func deref(typ Type) Type {
 }
 
 // defaultType returns the default "typed" type for an "untyped" type;
-// it returns the argument typ for all other types.
+// it returns the incoming type for all other types. If there is no
+// corresponding untyped type, the result is Typ[Invalid].
+//
 func defaultType(typ Type) Type {
 	if t, ok := typ.(*Basic); ok {
-		var k BasicKind
+		k := Invalid
 		switch t.Kind {
+		// case UntypedNil:
+		//      There is no default type for nil. For a good error message,
+		//      catch this case before calling this function.
 		case UntypedBool:
 			k = Bool
-		case UntypedRune:
-			k = Rune
 		case UntypedInt:
 			k = Int
+		case UntypedRune:
+			k = Rune
 		case UntypedFloat:
 			k = Float64
 		case UntypedComplex:
 			k = Complex128
 		case UntypedString:
 			k = String
-		default:
-			unreachable()
 		}
 		typ = Typ[k]
 	}

src/pkg/exp/types/stmt.go

@@ -12,9 +12,9 @@ import (
 )
 
 func (check *checker) assignOperand(z, x *operand) {
-	if t, ok := x.typ.(*tuple); ok {
+	if t, ok := x.typ.(*Result); ok {
 		// TODO(gri) elsewhere we use "assignment count mismatch" (consolidate)
-		check.errorf(x.pos(), "%d-valued expression %s used as single value", len(t.list), x)
+		check.errorf(x.pos(), "%d-valued expression %s used as single value", len(t.Values), x)
 		x.mode = invalid
 		return
 	}
@@ -95,7 +95,12 @@ func (check *checker) assign1to1(lhs, rhs ast.Expr, x *operand, decl bool, iota
 		if x.mode != invalid {
 			typ = x.typ
 			if obj.Kind == ast.Var && isUntyped(typ) {
-				typ = defaultType(typ)
+				if x.isNil() {
+					check.errorf(x.pos(), "use of untyped nil")
+					x.mode = invalid
+				} else {
+					typ = defaultType(typ)
+				}
 			}
 		}
 		obj.Type = typ
@@ -177,12 +182,12 @@ func (check *checker) assignNtoM(lhs, rhs []ast.Expr, decl bool, iota int) {
 			return
 		}
 
-		if t, ok := x.typ.(*tuple); ok && len(lhs) == len(t.list) {
+		if t, ok := x.typ.(*Result); ok && len(lhs) == len(t.Values) {
 			// function result
 			x.mode = value
-			for i, typ := range t.list {
+			for i, obj := range t.Values {
 				x.expr = nil // TODO(gri) should do better here
-				x.typ = typ
+				x.typ = obj.Type.(Type)
 				check.assign1to1(lhs[i], nil, &x, decl, iota)
 			}
 			return
@@ -429,7 +434,7 @@ func (check *checker) stmt(s ast.Stmt) {
 		var x operand
 		tag := s.Tag
 		if tag == nil {
-			// create true tag value and position it at the opening { of the switch
+			// use fake true tag value and position it at the opening { of the switch
 			tag = &ast.Ident{NamePos: s.Body.Lbrace, Name: "true", Obj: Universe.Lookup("true")}
 		}
 		check.expr(&x, tag, nil, -1)
@@ -451,15 +456,15 @@ func (check *checker) stmt(s ast.Stmt) {
 					}
 					// If we have a constant case value, it must appear only
 					// once in the switch statement. Determine if there is a
-					// duplicate entry, but only report an error there are no
-					// other errors.
+					// duplicate entry, but only report an error if there are
+					// no other errors.
 					var dupl token.Pos
 					if y.mode == constant {
 						// TODO(gri) This code doesn't work correctly for
 						//           large integer, floating point, or
 						//           complex values - the respective struct
-						//           comparison is shallow. Need to use a
-						//           has function to index the seen map.
+						//           comparisons are shallow. Need to use a
+						//           hash function to index the map.
 						dupl = seen[y.val]
 						seen[y.val] = y.pos()
 					}
@@ -475,7 +480,7 @@ func (check *checker) stmt(s ast.Stmt) {
 					}
 					check.comparison(&y, &x, token.EQL)
 					if y.mode != invalid && dupl.IsValid() {
-						check.errorf(y.pos(), "%s is duplicate case in switch\n\tprevious case at %s",
+						check.errorf(y.pos(), "%s is duplicate case (previous at %s)",
 							&y, check.fset.Position(dupl))
 					}
 				}

src/pkg/exp/types/testdata/decls1.src

@@ -46,7 +46,7 @@ var (
 	s14 = i << j /* ERROR "must be unsigned" */ 
 	s18 = math.Pi * 10.0
 	s19 = s1 /* ERROR "cannot call" */ ()
- 	s20 = f0 /* ERROR "used as single value" */ ()
+ 	s20 = f0 /* ERROR "no value" */ ()
 	s21 = f6(1, s1, i)
 	s22 = f6(1, s1, uu /* ERROR "cannot assign" */ )
 	
@@ -68,7 +68,7 @@ var (
 	t17 math /* ERROR "not a type" */ .Pi
 	t18 float64 = math.Pi * 10.0
 	t19 int = t1 /* ERROR "cannot call" */ ()
-	t20 int = f0 /* ERROR "used as single value" */ ()
+	t20 int = f0 /* ERROR "no value" */ ()
 )
 
 // Various more complex expressions
@@ -94,6 +94,7 @@ var (
 	v10 byte = 1024 /* ERROR "overflows" */
 	v11 = xx/yy*yy - xx
 	v12 = true && false
+	v13 = nil /* ERROR "use of untyped nil" */
 )
 
 // Multiple assignment expressions

src/pkg/exp/types/testdata/expr0.src

@@ -63,6 +63,7 @@ var (
 	u16 = &u0
 	u17 = *u16
 	u18 = <-u16 /* ERROR "cannot receive" */
+	u19 = ^uint(0)
 
 	// float64
 	f0 = float64(1)
@@ -131,5 +132,4 @@ var (
 	ch7 = <-ch
 	ch8 = <-rc
 	ch9 = <-sc /* ERROR "cannot receive" */
-
-)
\ No newline at end of file
+)

src/pkg/exp/types/testdata/expr2.src

@@ -6,6 +6,17 @@
 
 package expr2
 
+func _bool() {
+	const t = true == true
+	const f = true == false
+	_ = t /* ERROR "cannot compare" */ < f
+	_ = 0 /* ERROR "cannot convert" */ == t
+	var b bool
+	var x, y float32
+	b = x < y
+	_ = struct{b bool}{x < y}
+}
+
 // corner cases
 var (
 	v0 = nil /* ERROR "cannot compare" */ == nil

src/pkg/exp/types/testdata/expr3.src

@@ -286,3 +286,64 @@ func type_asserts() {
 	_ = t.(T2 /* ERROR "wrong type for method m" */ )
 	_ = t.(I2 /* ERROR "wrong type for method m" */ )
 }
+
+func f0() {}
+func f1(x int) {}
+func f2(u float32, s string) {}
+func fs(s []byte) {}
+func fv(x ...int) {}
+func fi(x ... interface{}) {}
+
+func g0() {}
+func g1() int { return 0}
+func g2() (u float32, s string) { return }
+func gs() []byte { return nil }
+
+func _calls() {
+	var x int
+	var y float32
+	var s []int
+
+	f0()
+	_ = f0 /* ERROR "used as value" */ ()
+	f0(g0 /* ERROR "too many arguments" */ )
+
+	f1(0)
+	f1(x)
+	f1(10.0)
+	f1 /* ERROR "too few arguments" */ ()
+	f1(x, y /* ERROR "too many arguments" */ )
+	f1(s /* ERROR "cannot assign" */ )
+	f1(x ... /* ERROR "cannot use ..." */ )
+	f1(g0 /* ERROR "used as value" */ ())
+	f1(g1())
+	// f1(g2()) // TODO(gri) missing position in error message
+
+	f2 /* ERROR "too few arguments" */ ()
+	f2 /* ERROR "too few arguments" */ (3.14)
+	f2(3.14, "foo")
+	f2(x /* ERROR "cannot assign" */ , "foo")
+	f2(g0 /* ERROR "used as value" */ ())
+	f2 /* ERROR "too few arguments" */ (g1 /* ERROR "cannot assign" */ ())
+	f2(g2())
+
+	fs /* ERROR "too few arguments" */ ()
+	fs(g0 /* ERROR "used as value" */ ())
+	fs(g1 /* ERROR "cannot assign" */ ())
+	// fs(g2()) // TODO(gri) missing position in error message
+	fs(gs())
+
+	fv()
+	fv(1, 2.0, x)
+	fv(s /* ERROR "cannot assign" */ )
+	fv(s...)
+	fv(1, s /* ERROR "can only use ... with matching parameter" */ ...)
+	fv(gs /* ERROR "cannot assign" */ ())
+	fv(gs /* ERROR "cannot assign" */ ()...)
+
+	fi()
+	fi(1, 2.0, x, 3.14, "foo")
+	fi(g2())
+	fi(0, g2)
+	fi(0, g2 /* ERROR "2-valued expression" */ ())
+}
\ No newline at end of file

src/pkg/exp/types/types.go

@@ -141,15 +141,15 @@ type Pointer struct {
 	Base Type
 }
 
-// A tuple represents a multi-value function return.
-// TODO(gri) use better name to avoid confusion (Go doesn't have tuples).
-type tuple struct {
+// A Result represents a (multi-value) function call result.
+// TODO(gri) consider using an empty Result (Values == nil)
+//           as representation for the novalue operand mode.
+type Result struct {
 	implementsType
-	list []Type
+	Values ObjList // Signature.Results of the function called
 }
 
 // A Signature represents a user-defined function type func(...) (...).
-// TODO(gri) consider using "tuples" to represent parameters and results (see comment on tuples).
 type Signature struct {
 	implementsType
 	Recv       *ast.Object // nil if not a method

src/pkg/exp/types/types_test.go

@@ -155,7 +155,7 @@ var testExprs = []testEntry{
 	dup("-f(10, 20)"),
 	dup("f(x + y, +3.1415)"),
 	{"func(a, b int) {}", "(func literal)"},
-	{"func(a, b int) []int {}()[x]", "(func literal)()[x]"},
+	{"func(a, b int) []int {}(1, 2)[x]", "(func literal)(1, 2)[x]"},
 	{"[]int{1, 2, 3}", "(composite literal)"},
 	{"[]int{1, 2, 3}[x:]", "(composite literal)[x:]"},
 	{"i.([]string)", "i.(...)"},