go/types: remove the renaming import of go/constant

For niceness, when go/exact was moved from x/tools, it
was renamed go/constant.

For simplicity, when go/types was moved from x/tools, its
imports of (now) go/constant were done with a rename:

    import exact "go/constant"

This kept the code just as it was before and avoided the issue
of what to call the internal constant called, um, constant.

But not all was hidden, as the text of some fields of structs and
the like leaked the old name, so things like "exact.Value" appeared
in type definitions and function signatures in the documentation.
This is unacceptable.

Fix the documentation issue by fixing the code. Rename the constant
constant constant_, and remove the renaming import.

This should go into 1.5. It's mostly a mechanical change, is
internal to the package, and fixes the documentation. It contains
no semantic changes except to fix a benchmark that was broken
in the original transition.

Fixes #11949.

Change-Id: Ieb94b6558535b504180b1378f19e8f5a96f92d3c
Reviewed-on: https://go-review.googlesource.com/13051Reviewed-by: Russ Cox <rsc@golang.org>

src/go/types/api.go

@@ -28,7 +28,7 @@ import (
 	"bytes"
 	"fmt"
 	"go/ast"
-	exact "go/constant" // Renamed to reduce diffs from x/tools.  TODO: remove
+	"go/constant"
 	"go/token"
 )
 
@@ -218,7 +218,7 @@ func (info *Info) ObjectOf(id *ast.Ident) Object {
 type TypeAndValue struct {
 	mode  operandMode
 	Type  Type
-	Value exact.Value // == constant.Value
+	Value constant.Value
 }
 
 // TODO(gri) Consider eliminating the IsVoid predicate. Instead, report
@@ -246,7 +246,7 @@ func (tv TypeAndValue) IsBuiltin() bool {
 // nil Value.
 func (tv TypeAndValue) IsValue() bool {
 	switch tv.mode {
-	case constant, variable, mapindex, value, commaok:
+	case constant_, variable, mapindex, value, commaok:
 		return true
 	}
 	return false

src/go/types/assignments.go

@@ -23,7 +23,7 @@ func (check *Checker) assignment(x *operand, T Type) bool {
 	switch x.mode {
 	case invalid:
 		return true // error reported before
-	case constant, variable, mapindex, value, commaok:
+	case constant_, variable, mapindex, value, commaok:
 		// ok
 	default:
 		unreachable()
@@ -74,7 +74,7 @@ func (check *Checker) initConst(lhs *Const, x *operand) {
 	}
 
 	// rhs must be a constant
-	if x.mode != constant {
+	if x.mode != constant_ {
 		check.errorf(x.pos(), "%s is not constant", x)
 		if lhs.typ == nil {
 			lhs.typ = Typ[Invalid]

src/go/types/builtins.go

@@ -8,7 +8,7 @@ package types
 
 import (
 	"go/ast"
-	exact "go/constant" // Renamed to reduce diffs from x/tools.  TODO: remove
+	"go/constant"
 	"go/token"
 )
 
@@ -138,13 +138,13 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 		// len(x)
 		mode := invalid
 		var typ Type
-		var val exact.Value
+		var val constant.Value
 		switch typ = implicitArrayDeref(x.typ.Underlying()); t := typ.(type) {
 		case *Basic:
 			if isString(t) && id == _Len {
-				if x.mode == constant {
-					mode = constant
-					val = exact.MakeInt64(int64(len(exact.StringVal(x.val))))
+				if x.mode == constant_ {
+					mode = constant_
+					val = constant.MakeInt64(int64(len(constant.StringVal(x.val))))
 				} else {
 					mode = value
 				}
@@ -157,8 +157,8 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 			// the expression s does not contain channel receives or
 			// function calls; in this case s is not evaluated."
 			if !check.hasCallOrRecv {
-				mode = constant
-				val = exact.MakeInt64(t.len)
+				mode = constant_
+				val = constant.MakeInt64(t.len)
 			}
 
 		case *Slice, *Chan:
@@ -178,7 +178,7 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 		x.mode = mode
 		x.typ = Typ[Int]
 		x.val = val
-		if check.Types != nil && mode != constant {
+		if check.Types != nil && mode != constant_ {
 			check.recordBuiltinType(call.Fun, makeSig(x.typ, typ))
 		}
 
@@ -228,8 +228,8 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 			return
 		}
 
-		if x.mode == constant && y.mode == constant {
-			x.val = exact.BinaryOp(x.val, token.ADD, exact.MakeImag(y.val))
+		if x.mode == constant_ && y.mode == constant_ {
+			x.val = constant.BinaryOp(x.val, token.ADD, constant.MakeImag(y.val))
 		} else {
 			x.mode = value
 		}
@@ -242,7 +242,7 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 		case Float64:
 			complexT = Typ[Complex128]
 		case UntypedInt, UntypedRune, UntypedFloat:
-			if x.mode == constant {
+			if x.mode == constant_ {
 				realT = defaultType(realT).(*Basic)
 				complexT = Typ[UntypedComplex]
 			} else {
@@ -257,11 +257,11 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 		}
 
 		x.typ = complexT
-		if check.Types != nil && x.mode != constant {
+		if check.Types != nil && x.mode != constant_ {
 			check.recordBuiltinType(call.Fun, makeSig(complexT, realT, realT))
 		}
 
-		if x.mode != constant {
+		if x.mode != constant_ {
 			// The arguments have now their final types, which at run-
 			// time will be materialized. Update the expression trees.
 			// If the current types are untyped, the materialized type
@@ -339,11 +339,11 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 			check.invalidArg(x.pos(), "%s must be a complex number", x)
 			return
 		}
-		if x.mode == constant {
+		if x.mode == constant_ {
 			if id == _Real {
-				x.val = exact.Real(x.val)
+				x.val = constant.Real(x.val)
 			} else {
-				x.val = exact.Imag(x.val)
+				x.val = constant.Imag(x.val)
 			}
 		} else {
 			x.mode = value
@@ -360,7 +360,7 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 			unreachable()
 		}
 
-		if check.Types != nil && x.mode != constant {
+		if check.Types != nil && x.mode != constant_ {
 			check.recordBuiltinType(call.Fun, makeSig(Typ[k], x.typ))
 		}
 		x.typ = Typ[k]
@@ -471,8 +471,8 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 			return
 		}
 
-		x.mode = constant
-		x.val = exact.MakeInt64(check.conf.alignof(x.typ))
+		x.mode = constant_
+		x.val = constant.MakeInt64(check.conf.alignof(x.typ))
 		x.typ = Typ[Uintptr]
 		// result is constant - no need to record signature
 
@@ -516,8 +516,8 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 		check.recordSelection(selx, FieldVal, base, obj, index, false)
 
 		offs := check.conf.offsetof(base, index)
-		x.mode = constant
-		x.val = exact.MakeInt64(offs)
+		x.mode = constant_
+		x.val = constant.MakeInt64(offs)
 		x.typ = Typ[Uintptr]
 		// result is constant - no need to record signature
 
@@ -528,8 +528,8 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 			return
 		}
 
-		x.mode = constant
-		x.val = exact.MakeInt64(check.conf.sizeof(x.typ))
+		x.mode = constant_
+		x.val = constant.MakeInt64(check.conf.sizeof(x.typ))
 		x.typ = Typ[Uintptr]
 		// result is constant - no need to record signature
 
@@ -537,15 +537,15 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 		// assert(pred) causes a typechecker error if pred is false.
 		// The result of assert is the value of pred if there is no error.
 		// Note: assert is only available in self-test mode.
-		if x.mode != constant || !isBoolean(x.typ) {
+		if x.mode != constant_ || !isBoolean(x.typ) {
 			check.invalidArg(x.pos(), "%s is not a boolean constant", x)
 			return
 		}
-		if x.val.Kind() != exact.Bool {
+		if x.val.Kind() != constant.Bool {
 			check.errorf(x.pos(), "internal error: value of %s should be a boolean constant", x)
 			return
 		}
-		if !exact.BoolVal(x.val) {
+		if !constant.BoolVal(x.val) {
 			check.errorf(call.Pos(), "%s failed", call)
 			// compile-time assertion failure - safe to continue
 		}

src/go/types/call.go

@@ -46,7 +46,7 @@ func (check *Checker) call(x *operand, e *ast.CallExpr) exprKind {
 		}
 		x.expr = e
 		// a non-constant result implies a function call
-		if x.mode != invalid && x.mode != constant {
+		if x.mode != invalid && x.mode != constant_ {
 			check.hasCallOrRecv = true
 		}
 		return predeclaredFuncs[id].kind
@@ -302,7 +302,7 @@ func (check *Checker) selector(x *operand, e *ast.SelectorExpr) {
 			switch exp := exp.(type) {
 			case *Const:
 				assert(exp.Val() != nil)
-				x.mode = constant
+				x.mode = constant_
 				x.typ = exp.typ
 				x.val = exp.val
 			case *TypeName:

src/go/types/check.go

@@ -8,7 +8,7 @@ package types
 
 import (
 	"go/ast"
-	exact "go/constant" // Renamed to reduce diffs from x/tools.  TODO: remove
+	"go/constant"
 	"go/token"
 )
 
@@ -36,7 +36,7 @@ type exprInfo struct {
 	isLhs bool // expression is lhs operand of a shift with delayed type-check
 	mode  operandMode
 	typ   *Basic
-	val   exact.Value // constant value; or nil (if not a constant)
+	val   constant.Value // constant value; or nil (if not a constant)
 }
 
 // funcInfo stores the information required for type-checking a function.
@@ -51,7 +51,7 @@ type funcInfo struct {
 type context struct {
 	decl          *declInfo      // package-level declaration whose init expression/function body is checked
 	scope         *Scope         // top-most scope for lookups
-	iota          exact.Value // value of iota in a constant declaration; nil otherwise
+	iota          constant.Value // value of iota in a constant declaration; nil otherwise
 	sig           *Signature     // function signature if inside a function; nil otherwise
 	hasLabel      bool           // set if a function makes use of labels (only ~1% of functions); unused outside functions
 	hasCallOrRecv bool           // set if an expression contains a function call or channel receive operation
@@ -126,7 +126,7 @@ func (check *Checker) assocMethod(tname string, meth *Func) {
 	m[tname] = append(m[tname], meth)
 }
 
-func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val exact.Value) {
+func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
 	m := check.untyped
 	if m == nil {
 		m = make(map[ast.Expr]exprInfo)
@@ -257,14 +257,14 @@ func (check *Checker) recordUntyped() {
 	}
 }
 
-func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val exact.Value) {
+func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) {
 	assert(x != nil)
 	assert(typ != nil)
 	if mode == invalid {
 		return // omit
 	}
 	assert(typ != nil)
-	if mode == constant {
+	if mode == constant_ {
 		assert(val != nil)
 		assert(typ == Typ[Invalid] || isConstType(typ))
 	}

src/go/types/conversions.go

@@ -6,12 +6,12 @@
 
 package types
 
-import exact "go/constant" // Renamed to reduce diffs from x/tools.  TODO: remove
+import "go/constant"
 
 // Conversion type-checks the conversion T(x).
 // The result is in x.
 func (check *Checker) conversion(x *operand, T Type) {
-	constArg := x.mode == constant
+	constArg := x.mode == constant_
 
 	var ok bool
 	switch {
@@ -22,13 +22,13 @@ func (check *Checker) conversion(x *operand, T Type) {
 			ok = true
 		case isInteger(x.typ) && isString(t):
 			codepoint := int64(-1)
-			if i, ok := exact.Int64Val(x.val); ok {
+			if i, ok := constant.Int64Val(x.val); ok {
 				codepoint = i
 			}
 			// If codepoint < 0 the absolute value is too large (or unknown) for
 			// conversion. This is the same as converting any other out-of-range
 			// value - let string(codepoint) do the work.
-			x.val = exact.MakeString(string(codepoint))
+			x.val = constant.MakeString(string(codepoint))
 			ok = true
 		}
 	case x.convertibleTo(check.conf, T):

src/go/types/decl.go

@@ -6,7 +6,7 @@ package types
 
 import (
 	"go/ast"
-	exact "go/constant" // Renamed to reduce diffs from x/tools.  TODO: remove
+	"go/constant"
 	"go/token"
 )
 
@@ -105,7 +105,7 @@ func (check *Checker) constDecl(obj *Const, typ, init ast.Expr) {
 	defer func() { check.iota = nil }()
 
 	// provide valid constant value under all circumstances
-	obj.val = exact.MakeUnknown()
+	obj.val = constant.MakeUnknown()
 
 	// determine type, if any
 	if typ != nil {
@@ -335,7 +335,7 @@ func (check *Checker) declStmt(decl ast.Decl) {
 					// declare all constants
 					lhs := make([]*Const, len(s.Names))
 					for i, name := range s.Names {
-						obj := NewConst(name.Pos(), pkg, name.Name, nil, exact.MakeInt64(int64(iota)))
+						obj := NewConst(name.Pos(), pkg, name.Name, nil, constant.MakeInt64(int64(iota)))
 						lhs[i] = obj
 
 						var init ast.Expr

src/go/types/object.go

@@ -8,7 +8,7 @@ import (
 	"bytes"
 	"fmt"
 	"go/ast"
-	exact "go/constant" // Renamed to reduce diffs from x/tools.  TODO: remove
+	"go/constant"
 	"go/token"
 )
 
@@ -143,15 +143,15 @@ func (obj *PkgName) Imported() *Package { return obj.imported }
 // A Const represents a declared constant.
 type Const struct {
 	object
-	val     exact.Value
+	val     constant.Value
 	visited bool // for initialization cycle detection
 }
 
-func NewConst(pos token.Pos, pkg *Package, name string, typ Type, val exact.Value) *Const {
+func NewConst(pos token.Pos, pkg *Package, name string, typ Type, val constant.Value) *Const {
 	return &Const{object{nil, pos, pkg, name, typ, 0, token.NoPos}, val, false}
 }
 
-func (obj *Const) Val() exact.Value { return obj.val }
+func (obj *Const) Val() constant.Value { return obj.val }
 
 // A TypeName represents a declared type.
 type TypeName struct {

src/go/types/operand.go

@@ -9,7 +9,7 @@ package types
 import (
 	"bytes"
 	"go/ast"
-	exact "go/constant" // Renamed to reduce diffs from x/tools.  TODO: remove
+	"go/constant"
 	"go/token"
 )
 
@@ -21,7 +21,7 @@ const (
 	novalue                      // operand represents no value (result of a function call w/o result)
 	builtin                      // operand is a built-in function
 	typexpr                      // operand is a type
-	constant                    // operand is a constant; the operand's typ is a Basic type
+	constant_                    // operand is a constant; the operand's typ is a Basic type
 	variable                     // operand is an addressable variable
 	mapindex                     // operand is a map index expression (acts like a variable on lhs, commaok on rhs of an assignment)
 	value                        // operand is a computed value
@@ -33,7 +33,7 @@ var operandModeString = [...]string{
 	novalue:   "no value",
 	builtin:   "built-in",
 	typexpr:   "type",
-	constant: "constant",
+	constant_: "constant",
 	variable:  "variable",
 	mapindex:  "map index expression",
 	value:     "value",
@@ -50,7 +50,7 @@ type operand struct {
 	mode operandMode
 	expr ast.Expr
 	typ  Type
-	val  exact.Value
+	val  constant.Value
 	id   builtinId
 }
 
@@ -105,7 +105,7 @@ func operandString(x *operand, qf Qualifier) string {
 			expr = predeclaredFuncs[x.id].name
 		case typexpr:
 			expr = TypeString(x.typ, qf)
-		case constant:
+		case constant_:
 			expr = x.val.String()
 		}
 	}
@@ -135,7 +135,7 @@ func operandString(x *operand, qf Qualifier) string {
 	buf.WriteString(operandModeString[x.mode])
 
 	// <val>
-	if x.mode == constant {
+	if x.mode == constant_ {
 		if s := x.val.String(); s != expr {
 			buf.WriteByte(' ')
 			buf.WriteString(s)
@@ -166,7 +166,7 @@ func (x *operand) String() string {
 
 // setConst sets x to the untyped constant for literal lit.
 func (x *operand) setConst(tok token.Token, lit string) {
-	val := exact.MakeFromLiteral(lit, tok, 0)
+	val := constant.MakeFromLiteral(lit, tok, 0)
 	if val == nil {
 		// TODO(gri) Should we make it an unknown constant instead?
 		x.mode = invalid
@@ -187,7 +187,7 @@ func (x *operand) setConst(tok token.Token, lit string) {
 		kind = UntypedString
 	}
 
-	x.mode = constant
+	x.mode = constant_
 	x.typ = Typ[kind]
 	x.val = val
 }
@@ -260,7 +260,7 @@ func (x *operand) assignableTo(conf *Config, T Type) bool {
 	if isUntyped(Vu) {
 		switch t := Tu.(type) {
 		case *Basic:
-			if x.mode == constant {
+			if x.mode == constant_ {
 				return representableConst(x.val, conf, t.kind, nil)
 			}
 			// The result of a comparison is an untyped boolean,
@@ -283,5 +283,5 @@ func (x *operand) assignableTo(conf *Config, T Type) bool {
 func (x *operand) isInteger() bool {
 	return x.mode == invalid ||
 		isInteger(x.typ) ||
-		isUntyped(x.typ) && x.mode == constant && representableConst(x.val, nil, UntypedInt, nil) // no *Config required for UntypedInt
+		isUntyped(x.typ) && x.mode == constant_ && representableConst(x.val, nil, UntypedInt, nil) // no *Config required for UntypedInt
 }

src/go/types/resolver.go

@@ -7,7 +7,7 @@ package types
 import (
 	"fmt"
 	"go/ast"
-	exact "go/constant" // Renamed to reduce diffs from x/tools.  TODO: remove
+	"go/constant"
 	"go/token"
 	pathLib "path"
 	"strconv"
@@ -256,7 +256,7 @@ func (check *Checker) collectObjects() {
 
 							// declare all constants
 							for i, name := range s.Names {
-								obj := NewConst(name.Pos(), pkg, name.Name, nil, exact.MakeInt64(int64(iota)))
+								obj := NewConst(name.Pos(), pkg, name.Name, nil, constant.MakeInt64(int64(iota)))
 
 								var init ast.Expr
 								if i < len(last.Values) {

src/go/types/self_test.go

@@ -47,7 +47,7 @@ func TestBenchmark(t *testing.T) {
 	// We're not using testing's benchmarking mechanism directly
 	// because we want custom output.
 
-	for _, p := range []string{"types", "exact", "gcimporter"} {
+	for _, p := range []string{"types", "constant", filepath.Join("internal", "gcimporter")} {
 		path := filepath.Join("..", p)
 		runbench(t, path, false)
 		runbench(t, path, true)

src/go/types/stmt.go

@@ -9,7 +9,7 @@ package types
 import (
 	"fmt"
 	"go/ast"
-	exact "go/constant" // Renamed to reduce diffs from x/tools.  TODO: remove
+	"go/constant"
 	"go/token"
 )
 
@@ -402,9 +402,9 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 		} else {
 			// spec: "A missing switch expression is
 			// equivalent to the boolean value true."
-			x.mode = constant
+			x.mode = constant_
 			x.typ = Typ[Bool]
-			x.val = exact.MakeBool(true)
+			x.val = constant.MakeBool(true)
 			x.expr = &ast.Ident{NamePos: s.Body.Lbrace, Name: "true"}
 		}
 

src/go/types/typexpr.go

@@ -8,7 +8,7 @@ package types
 
 import (
 	"go/ast"
-	exact "go/constant" // Renamed to reduce diffs from x/tools.  TODO: remove
+	"go/constant"
 	"go/token"
 	"sort"
 	"strconv"
@@ -65,7 +65,7 @@ func (check *Checker) ident(x *operand, e *ast.Ident, def *Named, path []*TypeNa
 			x.val = obj.val
 		}
 		assert(x.val != nil)
-		x.mode = constant
+		x.mode = constant_
 
 	case *TypeName:
 		x.mode = typexpr
@@ -367,7 +367,7 @@ func (check *Checker) typOrNil(e ast.Expr) Type {
 func (check *Checker) arrayLength(e ast.Expr) int64 {
 	var x operand
 	check.expr(&x, e)
-	if x.mode != constant {
+	if x.mode != constant_ {
 		if x.mode != invalid {
 			check.errorf(x.pos(), "array length %s must be constant", &x)
 		}
@@ -377,7 +377,7 @@ func (check *Checker) arrayLength(e ast.Expr) int64 {
 		check.errorf(x.pos(), "array length %s must be integer", &x)
 		return 0
 	}
-	n, ok := exact.Int64Val(x.val)
+	n, ok := constant.Int64Val(x.val)
 	if !ok || n < 0 {
 		check.errorf(x.pos(), "invalid array length %s", &x)
 		return 0

src/go/types/universe.go

@@ -7,7 +7,7 @@
 package types
 
 import (
-	exact "go/constant" // Renamed to reduce diffs from x/tools.  TODO: remove
+	"go/constant"
 	"go/token"
 	"strings"
 )
@@ -76,11 +76,11 @@ func defPredeclaredTypes() {
 var predeclaredConsts = [...]struct {
 	name string
 	kind BasicKind
-	val  exact.Value
+	val  constant.Value
 }{
-	{"true", UntypedBool, exact.MakeBool(true)},
-	{"false", UntypedBool, exact.MakeBool(false)},
-	{"iota", UntypedInt, exact.MakeInt64(0)},
+	{"true", UntypedBool, constant.MakeBool(true)},
+	{"false", UntypedBool, constant.MakeBool(false)},
+	{"iota", UntypedInt, constant.MakeInt64(0)},
 }
 
 func defPredeclaredConsts() {