gopls/internal/lsp/source/methodsets: comparable also has no package

Fix a crash where "error" is assumed to be the only named type with no
package.

Fixes golang/go#60544

Change-Id: I911296936f93429c780761979aeba38936b14428
Reviewed-on: https://go-review.googlesource.com/c/tools/+/499196
Reviewed-by: Alan Donovan <[email protected]>
Run-TryBot: Robert Findley <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
gopls-CI: kokoro <[email protected]>

Author: findleyr

gopls/internal/lsp/source/methodsets/methodsets.go

@@ -351,8 +351,8 @@ func fingerprint(method *types.Func) (string, bool) {
 			if tname.Pkg() != nil {
 				buf.WriteString(strconv.Quote(tname.Pkg().Path()))
 				buf.WriteByte('.')
-			} else if tname.Name() != "error" {
-				panic(tname) // error is the only named type with no package
+			} else if tname.Name() != "error" && tname.Name() != "comparable" {
+				panic(tname) // error and comparable the only named types with no package
 			}
 			buf.WriteString(tname.Name())
 

gopls/internal/regtest/marker/testdata/diagnostics/issue60544.txt

@@ -0,0 +1,13 @@
+This test exercises a crash due to treatment of "comparable" in methodset
+calculation (golang/go#60544).
+
+-min_go is 1.19 as the error message changed at this Go version.
+-- flags --
+-min_go=go1.19
+
+-- main.go --
+package main
+
+type X struct{}
+
+func (X) test(x comparable) {} //@diag("comparable", re"outside a type constraint")