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cmd/compile: adjust types2 shift check to match go/types (cleanup)

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With this change, the shift checking code matches the corresponding
go/types code, but for the differences in the internal error reporting,
and call of check.overflow.

The change leads to the recording of an untyped int value if the RHS
of a non-constant shift is an untyped integer value. Adjust the type
in the compiler's irgen accordingly. Add test/shift3.go to verify
behavior.

Change-Id: I20386fcb1d5c48becffdc2203081fb70c08b282d
Reviewed-on: https://go-review.googlesource.com/c/go/+/398236
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
This commit is contained in:
Robert Griesemer 2022-04-01 17:02:28 -07:00
parent 063f4032f5
commit c0bbeb0982
5 changed files with 126 additions and 15 deletions
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9
src/cmd/compile/internal/noder/expr.go
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@ -6,6 +6,7 @@ package noder
import (
"fmt"
"go/constant"
"cmd/compile/internal/base"
"cmd/compile/internal/ir"
@ -62,6 +63,14 @@ func (g *irgen) expr(expr syntax.Expr) ir.Node {
case types2.UntypedNil:
// ok; can appear in type switch case clauses
// TODO(mdempsky): Handle as part of type switches instead?
case types2.UntypedInt, types2.UntypedFloat, types2.UntypedComplex:
// Untyped rhs of non-constant shift, e.g. x << 1.0.
// If we have a constant value, it must be an int >= 0.
if tv.Value != nil {
s := constant.ToInt(tv.Value)
assert(s.Kind() == constant.Int && constant.Sign(s) >= 0)
}
typ = types2.Typ[types2.Uint]
case types2.UntypedBool:
typ = types2.Typ[types2.Bool] // expression in "if" or "for" condition
case types2.UntypedString: