Do not widen literal types when emitting declarations

Author: Andarist

src/compiler/checker.ts

@@ -47230,7 +47230,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         // Get type of the symbol if this is the valid symbol otherwise get type at location
         const symbol = getSymbolOfDeclaration(declaration);
         let type = symbol && !(symbol.flags & (SymbolFlags.TypeLiteral | SymbolFlags.Signature))
-            ? getWidenedLiteralType(getTypeOfSymbol(symbol))
+            ? getTypeOfSymbol(symbol)
             : errorType;
         if (
             type.flags & TypeFlags.UniqueESSymbol &&

tests/baselines/reference/ambientConstLiterals.js

@@ -74,5 +74,5 @@ declare const c9: {
 declare const c10: number[];
 declare const c11: string;
 declare const c12: number;
-declare const c13: string;
-declare const c14: number;
+declare const c13: "abc" | "def";
+declare const c14: 123 | 456;

tests/baselines/reference/declarationEmitBindingPatterns2.js

@@ -0,0 +1,16 @@
+//// [tests/cases/compiler/declarationEmitBindingPatterns2.ts] ////
+
+//// [declarationEmitBindingPatterns2.ts]
+// https://github.com/microsoft/TypeScript/issues/55439
+
+function foo(): { y: 1 } {
+  return { y: 1 };
+}
+
+export const { y = 0 } = foo();
+
+
+
+
+//// [declarationEmitBindingPatterns2.d.ts]
+export declare const y: 1 | 0;

tests/baselines/reference/declarationEmitBindingPatterns2.symbols

@@ -0,0 +1,17 @@
+//// [tests/cases/compiler/declarationEmitBindingPatterns2.ts] ////
+
+=== declarationEmitBindingPatterns2.ts ===
+// https://github.com/microsoft/TypeScript/issues/55439
+
+function foo(): { y: 1 } {
+>foo : Symbol(foo, Decl(declarationEmitBindingPatterns2.ts, 0, 0))
+>y : Symbol(y, Decl(declarationEmitBindingPatterns2.ts, 2, 17))
+
+  return { y: 1 };
+>y : Symbol(y, Decl(declarationEmitBindingPatterns2.ts, 3, 10))
+}
+
+export const { y = 0 } = foo();
+>y : Symbol(y, Decl(declarationEmitBindingPatterns2.ts, 6, 14))
+>foo : Symbol(foo, Decl(declarationEmitBindingPatterns2.ts, 0, 0))
+

tests/baselines/reference/declarationEmitBindingPatterns2.types

@@ -0,0 +1,21 @@
+//// [tests/cases/compiler/declarationEmitBindingPatterns2.ts] ////
+
+=== declarationEmitBindingPatterns2.ts ===
+// https://github.com/microsoft/TypeScript/issues/55439
+
+function foo(): { y: 1 } {
+>foo : () => {    y: 1;}
+>y : 1
+
+  return { y: 1 };
+>{ y: 1 } : { y: 1; }
+>y : 1
+>1 : 1
+}
+
+export const { y = 0 } = foo();
+>y : 1 | 0
+>0 : 0
+>foo() : { y: 1; }
+>foo : () => { y: 1; }
+

tests/baselines/reference/strictFunctionTypes1.js

@@ -82,7 +82,7 @@ declare function fs(x: string): void;
 declare function fx(f: (x: "def") => void): void;
 declare const x1: (x: string) => void;
 declare const x2 = "abc";
-declare const x3: string;
+declare const x3: "def" | "abc";
 declare const x4: Func<string>;
 declare const never: never;
 declare const x10: string;

tests/baselines/reference/stringLiteralTypesOverloads02.js

@@ -104,9 +104,9 @@ declare namespace Consts1 {
 declare const string = "string";
 declare const number = "number";
 declare const boolean = "boolean";
-declare const stringOrNumber: string;
-declare const stringOrBoolean: string;
-declare const booleanOrNumber: string;
-declare const stringOrBooleanOrNumber: string;
+declare const stringOrNumber: "string" | "number";
+declare const stringOrBoolean: "string" | "boolean";
+declare const booleanOrNumber: "number" | "boolean";
+declare const stringOrBooleanOrNumber: "string" | "number" | "boolean";
 declare namespace Consts2 {
 }

tests/cases/compiler/declarationEmitBindingPatterns2.ts

@@ -0,0 +1,11 @@
+// @strict: true
+// @declaration: true
+// @emitDeclarationOnly: true
+
+// https://github.com/microsoft/TypeScript/issues/55439
+
+function foo(): { y: 1 } {
+  return { y: 1 };
+}
+
+export const { y = 0 } = foo();