Check privateness when emittign readonly/const props (microsoft#26920)

Author: weswigham

src/compiler/transformers/declarations.ts

@@ -1324,12 +1324,13 @@ namespace ts {
     }
 
     type CanHaveLiteralInitializer = VariableDeclaration | PropertyDeclaration | PropertySignature | ParameterDeclaration;
-    function canHaveLiteralInitializer(node: Node): node is CanHaveLiteralInitializer {
+    function canHaveLiteralInitializer(node: Node): boolean {
         switch (node.kind) {
-            case SyntaxKind.VariableDeclaration:
             case SyntaxKind.PropertyDeclaration:
             case SyntaxKind.PropertySignature:
+                return !hasModifier(node, ModifierFlags.Private);
             case SyntaxKind.Parameter:
+            case SyntaxKind.VariableDeclaration:
                 return true;
         }
         return false;

tests/baselines/reference/declarationEmitPrivateReadonlyLiterals.js

@@ -0,0 +1,28 @@
+//// [declarationEmitPrivateReadonlyLiterals.ts]
+class Foo {
+    private static readonly A = "a";
+    private readonly B = "b";
+    private static readonly C = 42;
+    private readonly D = 42;
+}
+
+
+//// [declarationEmitPrivateReadonlyLiterals.js]
+var Foo = /** @class */ (function () {
+    function Foo() {
+        this.B = "b";
+        this.D = 42;
+    }
+    Foo.A = "a";
+    Foo.C = 42;
+    return Foo;
+}());
+
+
+//// [declarationEmitPrivateReadonlyLiterals.d.ts]
+declare class Foo {
+    private static readonly A;
+    private readonly B;
+    private static readonly C;
+    private readonly D;
+}

tests/baselines/reference/declarationEmitPrivateReadonlyLiterals.symbols

@@ -0,0 +1,17 @@
+=== tests/cases/compiler/declarationEmitPrivateReadonlyLiterals.ts ===
+class Foo {
+>Foo : Symbol(Foo, Decl(declarationEmitPrivateReadonlyLiterals.ts, 0, 0))
+
+    private static readonly A = "a";
+>A : Symbol(Foo.A, Decl(declarationEmitPrivateReadonlyLiterals.ts, 0, 11))
+
+    private readonly B = "b";
+>B : Symbol(Foo.B, Decl(declarationEmitPrivateReadonlyLiterals.ts, 1, 36))
+
+    private static readonly C = 42;
+>C : Symbol(Foo.C, Decl(declarationEmitPrivateReadonlyLiterals.ts, 2, 29))
+
+    private readonly D = 42;
+>D : Symbol(Foo.D, Decl(declarationEmitPrivateReadonlyLiterals.ts, 3, 35))
+}
+

tests/baselines/reference/declarationEmitPrivateReadonlyLiterals.types

@@ -0,0 +1,21 @@
+=== tests/cases/compiler/declarationEmitPrivateReadonlyLiterals.ts ===
+class Foo {
+>Foo : Foo
+
+    private static readonly A = "a";
+>A : "a"
+>"a" : "a"
+
+    private readonly B = "b";
+>B : "b"
+>"b" : "b"
+
+    private static readonly C = 42;
+>C : 42
+>42 : 42
+
+    private readonly D = 42;
+>D : 42
+>42 : 42
+}
+

tests/cases/compiler/declarationEmitPrivateReadonlyLiterals.ts

@@ -0,0 +1,8 @@
+// @declaration: true
+
+class Foo {
+    private static readonly A = "a";
+    private readonly B = "b";
+    private static readonly C = 42;
+    private readonly D = 42;
+}