internal/lsp/source: respond with the underlying type to Type Definit…

…ion requests for composite types

Go to Type Definition works for all composite types except maps because
it is not clear which type to return if both key and value are named types.

Fixes golang/go#45029

Change-Id: Ie14f333c51af11033e2494aaaac367d35e7dc87b
GitHub-Last-Rev: 94a0481
GitHub-Pull-Request: golang#292
Reviewed-on: https://go-review.googlesource.com/c/tools/+/304789
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
Trust: Rebecca Stambler <rstambler@golang.org>
Trust: Heschi Kreinick <heschi@google.com>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>

internal/lsp/source/identifier.go

@@ -323,6 +323,12 @@ func typeToObject(typ types.Type) types.Object {
 		return typ.Obj()
 	case *types.Pointer:
 		return typeToObject(typ.Elem())
+	case *types.Array:
+		return typeToObject(typ.Elem())
+	case *types.Slice:
+		return typeToObject(typ.Elem())
+	case *types.Chan:
+		return typeToObject(typ.Elem())
 	default:
 		return nil
 	}

internal/lsp/testdata/summary.txt.golden

@@ -16,7 +16,7 @@ SemanticTokenCount = 3
 SuggestedFixCount = 40
 FunctionExtractionCount = 13
 DefinitionsCount = 90
-TypeDefinitionsCount = 2
+TypeDefinitionsCount = 10
 HighlightsCount = 69
 ReferencesCount = 25
 RenamesCount = 33

internal/lsp/testdata/typdef/typdef.go

@@ -0,0 +1,38 @@
+package typdef
+
+type Struct struct { //@item(Struct, "Struct", "struct{...}", "struct")
+	Field string
+}
+
+type Int int //@item(Int, "Int", "int", "type")
+
+func _() {
+	var (
+		value Struct
+		point *Struct
+	)
+	_ = value //@typdef("value", Struct)
+	_ = point //@typdef("point", Struct)
+
+	var (
+		array   [3]Struct
+		slice   []Struct
+		ch      chan Struct
+		complex [3]chan *[5][]Int
+	)
+	_ = array   //@typdef("array", Struct)
+	_ = slice   //@typdef("slice", Struct)
+	_ = ch      //@typdef("ch", Struct)
+	_ = complex //@typdef("complex", Int)
+
+	var s struct {
+		x struct {
+			xx struct {
+				field1 []Struct
+				field2 []Int
+			}
+		}
+	}
+	s.x.xx.field1 //@typdef("field1", Struct)
+	s.x.xx.field2 //@typdef("field2", Int)
+}