fix(38840): omit completions for a spread like argument in a function definition (microsoft#38897)

Author: a-tarasyuk

src/services/completions.ts

@@ -962,12 +962,13 @@ namespace ts.Completions {
                     case SyntaxKind.PropertyAccessExpression:
                         propertyAccessToConvert = parent as PropertyAccessExpression;
                         node = propertyAccessToConvert.expression;
-                        if (node.end === contextToken.pos &&
-                            isCallExpression(node) &&
+                        if ((isCallExpression(node) || isFunctionLike(node)) &&
+                            node.end === contextToken.pos &&
                             node.getChildCount(sourceFile) &&
                             last(node.getChildren(sourceFile)).kind !== SyntaxKind.CloseParenToken) {
-                            // This is likely dot from incorrectly parsed call expression and user is starting to write spread
+                            // This is likely dot from incorrectly parsed expression and user is starting to write spread
                             // eg: Math.min(./**/)
+                            // const x = function (./**/) {}
                             return undefined;
                         }
                         break;

tests/cases/fourslash/completionWritingSpreadLikeArgument.ts

@@ -0,0 +1,33 @@
+/// <reference path='fourslash.ts'/>
+
+////const t0 = {
+////    x: function (./*0*/) {}
+////}
+////const t1 = {
+////    x: (./*1*/) => {}
+////}
+////const t2 = {
+////    x: function foo(./*2*/) => {}
+////}
+////const t3 = {
+////    x(./*3*/) {}
+////}
+////
+////const t4 = function (./*4*/) {}
+////const t5 = (./*5*/) => {}
+////function t6(./*6*/) {}
+////
+////class Foo {
+////    m(./*7*/) {}
+////}
+
+for (const marker of test.markers()) {
+    goTo.marker(marker);
+    verify.completions({ exact: undefined });
+
+    edit.insert(".");
+    verify.completions({ exact: undefined });
+
+    edit.insert(".");
+    verify.completions({ exact: undefined });
+}