test:overload anonymous reference

gopls/internal/lsp/source/references_gox.go

@@ -5,6 +5,7 @@
 package source
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"go/token"
@@ -586,10 +587,15 @@ func gopObjectsAt(info *typesutil.Info, file *ast.File, pos token.Pos) (map[type
 		}
 		targets[obj] = leaf
 	case *ast.FuncLit:
+		// Look up the implicit *types.Func (overload member)
 		obj := info.Implicits[leaf]
+		if obj == nil {
+			var buf bytes.Buffer
+			typesutil.WriteExpr(&buf, leaf)
+			return nil, nil, fmt.Errorf("%w for %q", errNoObjectFound, buf.String())
+		}
 		targets[obj] = leaf
 	}
-
 	if len(targets) == 0 {
 		return nil, nil, fmt.Errorf("objectAt: internal error: no targets") // can't happen
 	}

gopls/internal/regtest/misc/references_gox_test.go

@@ -0,0 +1,51 @@
+package misc
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	. "golang.org/x/tools/gopls/internal/lsp/regtest"
+)
+
+func TestReferencesOnOverloadMember(t *testing.T) {
+	const files = `
+-- go.mod --
+module mod.com
+
+go 1.12
+-- def.gop --
+func add = (
+	func(a, b int) int {
+		return a + b
+	}
+	func(a, b string) string {
+		return a + b
+	}
+)
+-- test.gop --
+println add(1,2)
+println add("Hello", "World")
+println add("Bye", "World")
+`
+	Run(t, files, func(t *testing.T, env *Env) {
+		env.OpenFile("test.gop")
+		loc := env.GoToDefinition(env.RegexpSearch("test.gop", `println (add)\("Hello", "World"\)`))
+		refs, err := env.Editor.References(env.Ctx, loc)
+		if err != nil {
+			t.Fatalf("references on (*s).Error failed: %v", err)
+		}
+		var buf strings.Builder
+		for _, ref := range refs {
+			fmt.Fprintf(&buf, "%s %s\n", env.Sandbox.Workdir.URIToPath(ref.URI), ref.Range)
+		}
+		got := buf.String()
+		want := "def.gop 4:1-4:25\n" + // anonymous overload func
+			"test.gop 1:8-1:11\n" +
+			"test.gop 2:8-2:11\n"
+		if diff := cmp.Diff(want, got); diff != "" {
+			t.Errorf("unexpected references on (*s).Error (-want +got):\n%s", diff)
+		}
+	})
+}