From 480da3ebd79c82ff135cb63ea1df5546584e25f4 Mon Sep 17 00:00:00 2001
From: Rebecca Stambler <rstambler@golang.org>
Date: Wed, 6 May 2020 22:26:25 -0400
Subject: [PATCH] internal/lsp: return early in completion where possible

This a pure cut-and-paste.

Fixes golang/go#38868

Change-Id: I2ff07134a8b9f6186bab737caceab8a34a8e2f44
Reviewed-on: https://go-review.googlesource.com/c/tools/+/232677
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
---
 internal/lsp/source/completion.go | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/internal/lsp/source/completion.go b/internal/lsp/source/completion.go
index fff371aae5..fe3ba16e17 100644
--- a/internal/lsp/source/completion.go
+++ b/internal/lsp/source/completion.go
@@ -455,6 +455,7 @@ func Completion(ctx context.Context, snapshot Snapshot, fh FileHandle, protoPos
 
 	pos := rng.Start
 
+	// Check if completion at this position is valid. If not, return early.
 	switch n := path[0].(type) {
 	case *ast.BasicLit:
 		// Skip completion inside any kind of literal.
@@ -465,6 +466,20 @@ func Completion(ctx context.Context, snapshot Snapshot, fh FileHandle, protoPos
 			// example, don't offer completions at "<>" in "foo(bar...<>").
 			return nil, nil, nil
 		}
+	case *ast.Ident:
+		// reject defining identifiers
+		if obj, ok := pkg.GetTypesInfo().Defs[n]; ok {
+			if v, ok := obj.(*types.Var); ok && v.IsField() && v.Embedded() {
+				// An anonymous field is also a reference to a type.
+			} else {
+				objStr := ""
+				if obj != nil {
+					qual := types.RelativeTo(pkg.GetTypes())
+					objStr = types.ObjectString(obj, qual)
+				}
+				return nil, nil, ErrIsDefinition{objStr: objStr}
+			}
+		}
 	}
 
 	opts := snapshot.View().Options()
@@ -557,19 +572,6 @@ func Completion(ctx context.Context, snapshot Snapshot, fh FileHandle, protoPos
 			}
 			return c.items, c.getSurrounding(), nil
 		}
-		// reject defining identifiers
-		if obj, ok := pkg.GetTypesInfo().Defs[n]; ok {
-			if v, ok := obj.(*types.Var); ok && v.IsField() && v.Embedded() {
-				// An anonymous field is also a reference to a type.
-			} else {
-				objStr := ""
-				if obj != nil {
-					qual := types.RelativeTo(pkg.GetTypes())
-					objStr = types.ObjectString(obj, qual)
-				}
-				return nil, nil, ErrIsDefinition{objStr: objStr}
-			}
-		}
 		if err := c.lexical(ctx); err != nil {
 			return nil, nil, err
 		}