fix(37150): ignore private fields in string index type checking (#37183)

src/compiler/checker.ts

@@ -32950,6 +32950,10 @@ namespace ts {
                 const propDeclaration = prop.valueDeclaration;
                 const name = propDeclaration && getNameOfDeclaration(propDeclaration);
 
+                if (name && isPrivateIdentifier(name)) {
+                    return;
+                }
+
                 // index is numeric and property name is not valid numeric literal
                 if (indexKind === IndexKind.Number && !(name ? isNumericName(name) : isNumericLiteralName(prop.escapedName))) {
                     return;

tests/baselines/reference/classIndexer5.js

@@ -0,0 +1,17 @@
+//// [classIndexer5.ts]
+class Foo {
+    [key: string]: number;
+
+    #a: boolean;
+    #b = false;
+}
+
+
+//// [classIndexer5.js]
+class Foo {
+    constructor() {
+        this.#b = false;
+    }
+    #a;
+    #b;
+}

tests/baselines/reference/classIndexer5.symbols

@@ -0,0 +1,14 @@
+=== tests/cases/compiler/classIndexer5.ts ===
+class Foo {
+>Foo : Symbol(Foo, Decl(classIndexer5.ts, 0, 0))
+
+    [key: string]: number;
+>key : Symbol(key, Decl(classIndexer5.ts, 1, 5))
+
+    #a: boolean;
+>#a : Symbol(Foo.#a, Decl(classIndexer5.ts, 1, 26))
+
+    #b = false;
+>#b : Symbol(Foo.#b, Decl(classIndexer5.ts, 3, 16))
+}
+

tests/baselines/reference/classIndexer5.types

@@ -0,0 +1,15 @@
+=== tests/cases/compiler/classIndexer5.ts ===
+class Foo {
+>Foo : Foo
+
+    [key: string]: number;
+>key : string
+
+    #a: boolean;
+>#a : boolean
+
+    #b = false;
+>#b : boolean
+>false : false
+}
+

tests/cases/compiler/classIndexer5.ts

@@ -0,0 +1,8 @@
+// @target: esnext
+
+class Foo {
+    [key: string]: number;
+
+    #a: boolean;
+    #b = false;
+}