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go/types: review of expr.go

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The changes from the (reviewed) dev.regabi copy of expr.go can be seen
by comparing patchset 2 and 7. The actual change is some small
improvements to readability and consistency in untyped conversion,
adding some missing documentation, and removing the "// REVIEW
INCOMPLETE" marker.

Note that expr.go diverges from types2 in its handling of untyped
conversion.

Change-Id: I13a85f6e08f43343e249818245aa857b1f4bf29c
Reviewed-on: https://go-review.googlesource.com/c/go/+/295729
Trust: Robert Findley <rfindley@google.com>
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Rob Findley 2021-02-23 16:29:33 -05:00 committed by Robert Findley
parent b98ce3b606
commit a69c45213d
1 changed files with 18 additions and 12 deletions
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30
src/go/types/expr.go
View file

@ -1,4 +1,3 @@
// REVIEW INCOMPLETE
// Copyright 2012 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.
@ -100,8 +99,8 @@ func (check *Checker) overflow(x *operand, op token.Token, opPos token.Pos) {
// Typed constants must be representable in
// their type after each constant operation.
if typ := asBasic(x.typ); typ != nil && isTyped(typ) {
check.representable(x, typ)
if isTyped(x.typ) {
check.representable(x, asBasic(x.typ))
return
}
@ -191,10 +190,9 @@ func (check *Checker) unary(x *operand, e *ast.UnaryExpr) {
// nothing to do (and don't cause an error below in the overflow check)
return
}
typ := asBasic(x.typ)
var prec uint
if isUnsigned(typ) {
prec = uint(check.conf.sizeof(typ) * 8)
if isUnsigned(x.typ) {
prec = uint(check.conf.sizeof(x.typ) * 8)
}
x.val = constant.UnaryOp(e.Op, x.val, prec)
x.expr = e
@ -400,14 +398,20 @@ func representableConst(x constant.Value, check *Checker, typ *Basic, rounded *c
// representable checks that a constant operand is representable in the given
// basic type.
func (check *Checker) representable(x *operand, typ *Basic) {
if v, code := check.representation(x, typ); code != 0 {
v, code := check.representation(x, typ)
if code != 0 {
check.invalidConversion(code, x, typ)
x.mode = invalid
} else if v != nil {
x.val = v
return
}
assert(v != nil)
x.val = v
}
// representation returns the representation of the constant operand x as the
// basic type typ.
//
// If no such representation is possible, it returns a non-zero error code.
func (check *Checker) representation(x *operand, typ *Basic) (constant.Value, errorCode) {
assert(x.mode == constant_)
v := x.val
@ -593,7 +597,10 @@ func (check *Checker) convertUntyped(x *operand, target Type) {
// implicitTypeAndValue returns the implicit type of x when used in a context
// where the target type is expected. If no such implicit conversion is
// possible, it returns a nil Type.
// possible, it returns a nil Type and non-zero error code.
//
// If x is a constant operand, the returned constant.Value will be the
// representation of x in this context.
func (check *Checker) implicitTypeAndValue(x *operand, target Type) (Type, constant.Value, errorCode) {
target = expand(target)
if x.mode == invalid || isTyped(x.typ) || target == Typ[Invalid] {
@ -994,9 +1001,8 @@ func (check *Checker) binary(x *operand, e ast.Expr, lhs, rhs ast.Expr, op token
// x.typ is unchanged
return
}
typ := asBasic(x.typ)
// force integer division of integer operands
if op == token.QUO && isInteger(typ) {
if op == token.QUO && isInteger(x.typ) {
op = token.QUO_ASSIGN
}
x.val = constant.BinaryOp(x.val, op, y.val)