cmd/compile: enable more lenient type inference for untyped arguments

This enables the implementation for proposal #58671, which is
a likely accept. By enabling it early we get a bit extra soak
time for this feature. The change can be reverted trivially, if
need be.

For #58671.

Change-Id: Id6c27515e45ff79f4f1d2fc1706f3f672ccdd1ab
Reviewed-on: https://go-review.googlesource.com/c/go/+/495955
Run-TryBot: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/test/fixedbugs/issue58671.go b/test/fixedbugs/issue58671.go
new file mode 100644
index 0000000000..ae8f7a3ad6
--- /dev/null
+++ b/test/fixedbugs/issue58671.go
@@ -0,0 +1,19 @@
+// run
+
+// Copyright 2023 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.
+
+package main
+
+func g[P any](...P) P { var zero P; return zero }
+
+var (
+	_ int        = g(1, 2)
+	_ rune       = g(1, 'a')
+	_ float64    = g(1, 'a', 2.3)
+	_ float64    = g('a', 2.3)
+	_ complex128 = g(2.3, 'a', 1i)
+)
+
+func main() {}