Fix missing abstract keyword in completion (microsoft#45710)

* first commit

* tests

Author: sangxxh

Diff for: src/harness/fourslashInterfaceImpl.ts

@@ -1292,6 +1292,7 @@ namespace FourSlashInterface {
             "let",
             "package",
             "yield",
+            "abstract",
             "as",
             "asserts",
             "any",
@@ -1495,6 +1496,7 @@ namespace FourSlashInterface {
             "let",
             "package",
             "yield",
+            "abstract",
             "as",
             "asserts",
             "any",

Diff for: src/services/completions.ts

@@ -2960,6 +2960,7 @@ namespace ts.Completions {
                         || kind === SyntaxKind.ModuleKeyword
                         || kind === SyntaxKind.TypeKeyword
                         || kind === SyntaxKind.NamespaceKeyword
+                        || kind === SyntaxKind.AbstractKeyword
                         || isTypeKeyword(kind) && kind !== SyntaxKind.UndefinedKeyword;
                 case KeywordCompletionFilters.FunctionLikeBodyKeywords:
                     return isFunctionLikeBodyKeyword(kind);

Diff for: tests/baselines/reference/completionsCommentsClass.baseline

@@ -3672,6 +3672,18 @@
             }
           ]
         },
+        {
+          "name": "abstract",
+          "kind": "keyword",
+          "kindModifiers": "",
+          "sortText": "15",
+          "displayParts": [
+            {
+              "text": "abstract",
+              "kind": "keyword"
+            }
+          ]
+        },
         {
           "name": "as",
           "kind": "keyword",

Diff for: tests/baselines/reference/completionsCommentsClassMembers.baseline

@@ -86508,6 +86508,18 @@
             }
           ]
         },
+        {
+          "name": "abstract",
+          "kind": "keyword",
+          "kindModifiers": "",
+          "sortText": "15",
+          "displayParts": [
+            {
+              "text": "abstract",
+              "kind": "keyword"
+            }
+          ]
+        },
         {
           "name": "as",
           "kind": "keyword",
@@ -91852,6 +91864,18 @@
             }
           ]
         },
+        {
+          "name": "abstract",
+          "kind": "keyword",
+          "kindModifiers": "",
+          "sortText": "15",
+          "displayParts": [
+            {
+              "text": "abstract",
+              "kind": "keyword"
+            }
+          ]
+        },
         {
           "name": "as",
           "kind": "keyword",

Diff for: tests/baselines/reference/completionsCommentsCommentParsing.baseline

@@ -23145,6 +23145,18 @@
             }
           ]
         },
+        {
+          "name": "abstract",
+          "kind": "keyword",
+          "kindModifiers": "",
+          "sortText": "15",
+          "displayParts": [
+            {
+              "text": "abstract",
+              "kind": "keyword"
+            }
+          ]
+        },
         {
           "name": "as",
           "kind": "keyword",
@@ -41018,6 +41030,18 @@
             }
           ]
         },
+        {
+          "name": "abstract",
+          "kind": "keyword",
+          "kindModifiers": "",
+          "sortText": "15",
+          "displayParts": [
+            {
+              "text": "abstract",
+              "kind": "keyword"
+            }
+          ]
+        },
         {
           "name": "as",
           "kind": "keyword",

Diff for: tests/baselines/reference/completionsCommentsFunctionExpression.baseline

@@ -3579,6 +3579,18 @@
             }
           ]
         },
+        {
+          "name": "abstract",
+          "kind": "keyword",
+          "kindModifiers": "",
+          "sortText": "15",
+          "displayParts": [
+            {
+              "text": "abstract",
+              "kind": "keyword"
+            }
+          ]
+        },
         {
           "name": "as",
           "kind": "keyword",
@@ -8289,6 +8301,18 @@
             }
           ]
         },
+        {
+          "name": "abstract",
+          "kind": "keyword",
+          "kindModifiers": "",
+          "sortText": "15",
+          "displayParts": [
+            {
+              "text": "abstract",
+              "kind": "keyword"
+            }
+          ]
+        },
         {
           "name": "as",
           "kind": "keyword",