[dev.typeparams] cmd/compile: use dictionary to convert arguments of ==, != to interfaces

When comparing a value whose type is a type parameter to an interface,
we need to convert that type parameter to an interface using the dictionary
entries.

Change-Id: I409c9e36e376fe4ef8163407d0fd4e84496d5b65
Reviewed-on: https://go-review.googlesource.com/c/go/+/334150
Trust: Keith Randall <khr@golang.org>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>

1 files changed, 71 insertions, 0 deletions

diff --git a/test/typeparam/equal.go b/test/typeparam/equal.go
new file mode 100644
index 0000000000..6776b19d12
--- /dev/null
+++ b/test/typeparam/equal.go
@@ -0,0 +1,71 @@
+// run -gcflags=-G=3
+
+// Copyright 2021 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.
+
+// comparisons of type parameters to interfaces
+
+package main
+
+func f[T comparable](t, u T) bool {
+	// Comparing two type parameters directly.
+	// (Not really testing comparisons to interfaces, but just 'cause we're here.)
+	return t == u
+}
+
+func g[T comparable](t T, i interface{}) bool {
+	// Compare type parameter value to empty interface.
+	return t == i
+}
+
+type I interface {
+	foo()
+}
+
+type C interface {
+	comparable
+	I
+}
+
+func h[T C](t T, i I) bool {
+	// Compare type parameter value to nonempty interface.
+	return t == i
+}
+
+type myint int
+
+func (x myint) foo() {
+}
+
+func k[T comparable](t T, i interface{}) bool {
+	// Compare derived type value to interface.
+	return struct{a, b T}{t, t} == i
+}
+
+func main() {
+	assert(f(3, 3))
+	assert(!f(3, 5))
+	assert(g(3, 3))
+	assert(!g(3, 5))
+	assert(h(myint(3), myint(3)))
+	assert(!h(myint(3), myint(5)))
+
+	type S struct { a, b float64 }
+
+	assert(f(S{3,5}, S{3,5}))
+	assert(!f(S{3,5}, S{4,6}))
+	assert(g(S{3,5}, S{3,5}))
+	assert(!g(S{3,5}, S{4,6}))
+
+	assert(k(3, struct{a, b int}{3, 3}))
+	assert(!k(3, struct{a, b int}{3, 4}))
+}
+
+func assert(b bool)  {
+	if !b {
+		panic("assertion failed")
+	}
+}
+
+