internal/lsp/source: fixes completion for slice literals of pointers

The existing implementation did not suggest struct field names
when running completion from within a slice literal of
pointers. Now, struct field names are suggested in that case.

Fixes golang/go#33211

Change-Id: I6028420a9a789846b070fcc6e45ec89dc4d898d4
Reviewed-on: https://go-review.googlesource.com/c/tools/+/192277
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

internal/lsp/source/completion.go

@@ -765,7 +765,7 @@ func enclosingCompositeLiteral(path []ast.Node, pos token.Pos, info *types.Info)
 
 			clInfo := compLitInfo{
 				cl:     n,
-				clType: tv.Type.Underlying(),
+				clType: deref(tv.Type).Underlying(),
 			}
 
 			var (

internal/lsp/testdata/complit/complit.go.in

@@ -16,6 +16,11 @@ func _() {
 		//@complete("", fieldX)
 		Y: 1,
 	}
+	_ = []*position{
+        {
+            //@complete("", fieldX, fieldY, structPosition)
+        },
+	}
 }
 
 func _() {

internal/lsp/tests/tests.go

@@ -29,7 +29,7 @@ import (
 // We hardcode the expected number of test cases to ensure that all tests
 // are being executed. If a test is added, this number must be changed.
 const (
-	ExpectedCompletionsCount       = 154
+	ExpectedCompletionsCount       = 155
 	ExpectedCompletionSnippetCount = 15
 	ExpectedDiagnosticsCount       = 21
 	ExpectedFormatCount            = 6