go/types, types2: print underlying type of comparable as "interface{comparable}"

For #50791.

Change-Id: Ib12009d2895146e55ec3a51aa8ceafe58dfd82a5
Reviewed-on: https://go-review.googlesource.com/c/go/+/380754
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

4 files changed, 33 insertions, 12 deletions

diff --git a/src/cmd/compile/internal/types2/typestring.go b/src/cmd/compile/internal/types2/typestring.go
index 4d03eba657..ada0529929 100644
--- a/src/cmd/compile/internal/types2/typestring.go
+++ b/src/cmd/compile/internal/types2/typestring.go
@@ -201,12 +201,18 @@ func (w *typeWriter) typ(typ Type) {
 		}
 
 	case *Interface:
-		if t == universeAny.Type() && w.ctxt == nil {
-			// When not hashing, we can try to improve type strings by writing "any"
-			// for a type that is pointer-identical to universeAny. This logic should
-			// be deprecated by more robust handling for aliases.
-			w.string("any")
-			break
+		if w.ctxt == nil {
+			if t == universeAny.Type() {
+				// When not hashing, we can try to improve type strings by writing "any"
+				// for a type that is pointer-identical to universeAny. This logic should
+				// be deprecated by more robust handling for aliases.
+				w.string("any")
+				break
+			}
+			if t == universeComparable.Type().(*Named).underlying {
+				w.string("interface{comparable}")
+				break
+			}
 		}
 		if t.implicit {
 			if len(t.methods) == 0 && len(t.embeddeds) == 1 {
diff --git a/src/cmd/compile/internal/types2/typestring_test.go b/src/cmd/compile/internal/types2/typestring_test.go
index eda6835588..c0689e866c 100644
--- a/src/cmd/compile/internal/types2/typestring_test.go
+++ b/src/cmd/compile/internal/types2/typestring_test.go
@@ -93,6 +93,10 @@ var independentTestTypes = []testEntry{
 	dup(`interface{String() string; m(int) float32}`),
 	dup("interface{int|float32|complex128}"),
 	dup("interface{int|~float32|~complex128}"),
+	dup("any"),
+	dup("interface{comparable}"),
+	{"comparable", "interface{comparable}"},
+	{"error", "interface{Error() string}"},
 
 	// maps
 	dup("map[string]int"),
diff --git a/src/go/types/typestring.go b/src/go/types/typestring.go
index cf86f9f720..80210a2f34 100644
--- a/src/go/types/typestring.go
+++ b/src/go/types/typestring.go
@@ -202,12 +202,18 @@ func (w *typeWriter) typ(typ Type) {
 		}
 
 	case *Interface:
-		if t == universeAny.Type() && w.ctxt == nil {
-			// When not hashing, we can try to improve type strings by writing "any"
-			// for a type that is pointer-identical to universeAny. This logic should
-			// be deprecated by more robust handling for aliases.
-			w.string("any")
-			break
+		if w.ctxt == nil {
+			if t == universeAny.Type() {
+				// When not hashing, we can try to improve type strings by writing "any"
+				// for a type that is pointer-identical to universeAny. This logic should
+				// be deprecated by more robust handling for aliases.
+				w.string("any")
+				break
+			}
+			if t == universeComparable.Type().(*Named).underlying {
+				w.string("interface{comparable}")
+				break
+			}
 		}
 		if t.implicit {
 			if len(t.methods) == 0 && len(t.embeddeds) == 1 {
diff --git a/src/go/types/typestring_test.go b/src/go/types/typestring_test.go
index 14ab9b6002..b7b843516e 100644
--- a/src/go/types/typestring_test.go
+++ b/src/go/types/typestring_test.go
@@ -97,6 +97,11 @@ var independentTestTypes = []testEntry{
 	dup(`interface{String() string; m(int) float32}`),
 	dup("interface{int|float32|complex128}"),
 	dup("interface{int|~float32|~complex128}"),
+	dup("any"),
+	dup("interface{comparable}"),
+	// TODO(gri) adjust test for EvalCompositeTest
+	// {"comparable", "interface{comparable}"},
+	// {"error", "interface{Error() string}"},
 
 	// maps
 	dup("map[string]int"),