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

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>

1 files changed, 41 insertions, 0 deletions

diff --git a/test/shift3.go b/test/shift3.go
new file mode 100644
index 00000000000..bed2fd66ef7
--- /dev/null
+++ b/test/shift3.go
@@ -0,0 +1,41 @@
+// run
+
+// Copyright 2022 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.
+
+// Test that the compiler's noder uses the correct type
+// for RHS shift operands that are untyped. Must compile;
+// run for good measure.
+
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func f(x, y int) {
+	if x != y {
+		panic(fmt.Sprintf("%d != %d", x, y))
+	}
+}
+
+func main() {
+	var x int = 1
+	f(x<<1, 2)
+	f(x<<1., 2)
+	f(x<<(1+0i), 2)
+	f(x<<0i, 1)
+
+	f(x<<(1<<x), 4)
+	f(x<<(1.<<x), 4)
+	f(x<<((1+0i)<<x), 4)
+	f(x<<(0i<<x), 1)
+
+	// corner cases
+	const M = math.MaxUint
+	f(x<<(M+0), 0)     // shift by untyped int representable as uint
+	f(x<<(M+0.), 0)    // shift by untyped float representable as uint
+	f(x<<(M+0.+0i), 0) // shift by untyped complex representable as uint
+}