ignore trigger chars within a string literal

Author: a-tarasyuk

src/services/completions.ts

@@ -40,7 +40,9 @@ namespace ts.Completions {
         const compilerOptions = program.getCompilerOptions();
 
         const contextToken = findPrecedingToken(position, sourceFile);
-        if (triggerCharacter && !isValidTrigger(sourceFile, triggerCharacter, contextToken, position)) return undefined;
+        if (triggerCharacter && !isInString(sourceFile, position, contextToken) && !isValidTrigger(sourceFile, triggerCharacter, contextToken, position)) {
+            return undefined;
+        }
 
         const stringCompletions = StringCompletions.getStringLiteralCompletions(sourceFile, position, contextToken, typeChecker, compilerOptions, host, log, preferences);
         if (stringCompletions) {

tests/cases/fourslash/completionsStringsWithTriggerCharacter.ts

@@ -0,0 +1,30 @@
+/// <reference path="fourslash.ts" />
+
+//// type A = "a/b" | "b/a";
+//// const a: A = "a/*1*/";
+////
+//// type B = "a@b" | "b@a";
+//// const a: B = "a@/*2*/";
+////
+//// type C = "a.b" | "b.a";
+//// const c: C = "a./*3*/";
+////
+//// type D = "a'b" | "b'a";
+//// const d: D = "a'/*4*/";
+////
+//// type E = "a`b" | "b`a";
+//// const e: E = "a`/*5*/";
+////
+//// type F = 'a"b' | 'b"a';
+//// const f: F = 'a"/*6*/';
+////
+//// type G = "a<b" | "b<a";
+//// const g: G = 'a</*7*/';
+
+verify.completions({ marker: '1', exact: ["a/b", "b/a"], triggerCharacter: "/" });
+verify.completions({ marker: "2", exact: ["a@b", "b@a"], triggerCharacter: "@" });
+verify.completions({ marker: "3", exact: ["a.b", "b.a"], triggerCharacter: "." });
+verify.completions({ marker: "4", exact: ["a'b", "b'a"], triggerCharacter: "'" });
+verify.completions({ marker: "5", exact: ["a`b", "b`a"], triggerCharacter: "`" });
+verify.completions({ marker: "6", exact: ['a"b', 'b"a'], triggerCharacter: '"' });
+verify.completions({ marker: "7", exact: ["a<b", "b<a"], triggerCharacter: '<' });