Fixed element access expression writes for divergent write types (#55585)

tests/cases/compiler/divergentAccessorsTypes7.ts

@@ -6,12 +6,12 @@ class Test<S> {
     get value(): string {
         return null!;
     }
-    
+
     // -- Replacing the getter such that the getter/setter types match, removes the error:
     // get value(): string | ((item: S) => string) {
     //     return null!;
     // }
-    
+
     // -- Or, replacing the setter such that a concrete type is used, removes the error:
     // set value(value: string | ((item: { property: string }) => string)) {}
 }
@@ -21,3 +21,4 @@ const a = new Test<{
 }>();
 
 a.value = (item) => item.property
+a['value'] = (item) => item.property

tests/cases/compiler/divergentAccessorsTypes8.ts

@@ -0,0 +1,153 @@
+// @strict: true
+// @lib: esnext, dom
+// @noEmit: true
+
+export {}
+
+interface Serializer {
+  set value(v: string | number | boolean);
+  get value(): string;
+}
+declare let box: Serializer;
+const v = box['value']
+box['value'] = true;
+box['value'] = 42;
+box['value'] = "hello";
+
+interface Element {
+    get style(): CSSStyleDeclaration;
+    set style(cssText: string);
+}
+
+declare const element: Element;
+element['style'] = "color: red";
+element['style'] = element.style;
+
+class One {
+  get prop1(): string {
+    return "";
+  }
+  set prop1(s: string | number) {}
+
+  get prop2(): string {
+    return "";
+  }
+  set prop2(s: string | number) {}
+
+  prop3: number = 42;
+
+  get prop4(): string {
+    return "";
+  }
+  set prop4(s: string | number) {}
+}
+
+class Two {
+  get prop1(): string {
+    return "";
+  }
+  set prop1(s: string | number) {}
+
+  get prop2(): string {
+    return "";
+  }
+  set prop2(s: string) {}
+
+  get prop3(): string {
+    return "";
+  }
+  set prop3(s: string | boolean) {}
+
+  get prop4(): string {
+    return "";
+  }
+  set prop4(s: string | boolean) {}
+}
+
+declare const u1: One | Two;
+
+u1['prop1'] = 42;
+u1['prop1'] = "hello";
+
+u1['prop2'] = 42;
+u1['prop2'] = "hello";
+
+u1['prop3'] = 42;
+u1['prop3'] = "hello";
+u1['prop3'] = true;
+
+u1['prop4'] = 42;
+u1['prop4'] = "hello";
+u1['prop4'] = true;
+
+declare const i: One & Two;
+
+const iv1 = i['prop1'];
+i['prop1'] = 42;
+i['prop1'] = "hello";
+
+const iv2 = i['prop2'];
+i['prop2'] = 42;
+i['prop2'] = "hello";
+
+class Three {
+  get prop1(): string {
+    return "";
+  }
+  set prop1(s: string | number) {}
+
+  prop2: number = 42;
+}
+
+class Four {
+  get prop1(): "hello" {
+    return "hello";
+  }
+  set prop1(s: "hello" | number) {}
+
+  get prop2(): string {
+    return "";
+  }
+  set prop2(s: string | 42) {}
+}
+
+class Five {
+  get prop1(): "hello" {
+    return "hello";
+  }
+  set prop1(s: "hello" | boolean) {}
+
+  get prop2(): string {
+    return "";
+  }
+  set prop2(s: string | number | boolean) {}
+}
+
+declare const i2: Three & Four & Five;
+
+i2['prop1'] = 42;
+i2['prop1'] = "hello";
+
+i2['prop2'] = 42;
+i2['prop2'] = "hello";
+
+class Six {
+  get prop1(): boolean | number {
+    return 42;
+  }
+  set prop1(s: boolean | string) {}
+
+  get prop2(): bigint | number {
+    return 10;
+  }
+  set prop2(s: boolean | null) {}
+}
+
+declare const s1: Six
+declare const k1: 'prop1' | 'prop2'
+
+const sv1 = s1[k1]
+s1[k1] = 42
+s1[k1] = true
+s1[k1] = ''
+s1[k1] = null

tests/cases/fourslash/quickInfoOnElementAccessInWriteLocation1.ts

@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts'/>
+
+// @strict: true
+// @exactOptionalPropertyTypes: true
+//// declare const xx: { prop?: number };
+//// xx['prop'/*1*/] = 1;
+
+verify.quickInfoAt('1', '(property) prop?: number');

tests/cases/fourslash/quickInfoOnElementAccessInWriteLocation2.ts

@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts'/>
+
+// @strict: true
+// @exactOptionalPropertyTypes: true
+//// declare const xx: { prop?: number };
+//// xx['prop'/*1*/] += 1;
+
+verify.quickInfoAt('1', '(property) prop?: number');

tests/cases/fourslash/quickInfoOnElementAccessInWriteLocation3.ts

@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts'/>
+
+// @strict: true
+// @exactOptionalPropertyTypes: true
+//// declare const xx: { prop?: number };
+//// xx['prop'/*1*/] ??= 1;
+
+verify.quickInfoAt('1', '(property) prop?: number');

tests/cases/fourslash/quickInfoOnElementAccessInWriteLocation4.ts

@@ -0,0 +1,11 @@
+/// <reference path='fourslash.ts'/>
+
+// @strict: true
+//// interface Serializer {
+////   set value(v: string | number | boolean);
+////   get value(): string;
+//// }
+//// declare let box: Serializer;
+//// box['value'/*1*/] = true;
+
+verify.quickInfoAt('1', '(property) Serializer.value: string | number | boolean');

tests/cases/fourslash/quickInfoOnElementAccessInWriteLocation5.ts

@@ -0,0 +1,11 @@
+/// <reference path='fourslash.ts'/>
+
+// @strict: true
+//// interface Serializer {
+////   set value(v: string | number);
+////   get value(): string;
+//// }
+//// declare let box: Serializer;
+//// box['value'/*1*/] += 10;
+
+verify.quickInfoAt('1', '(property) Serializer.value: string | number');