Add static index signature (#37797)

* Add static index

* fix lint

* make lint happy

* adjust test cases

* add more cases

* fix changes

* Add more case

* accept baseline

* fix error if extends others

* Update vfsUtil.ts

* use equal to empty array

* static signature of interface is an error

* Accept baseline

* Check index constraints for static signature

* Accpet baseline

* Fix crash

* fix crash

* Accept baseline

* Fix regression

* Fix crash

* always return new array

tests/cases/compiler/staticIndexer.ts

@@ -1,3 +0,0 @@
-class C {
-    static [s: string]: number;
-}

tests/cases/conformance/classes/staticIndexSignature/staticIndexSignature1.ts

@@ -0,0 +1,11 @@
+class C {
+    static [s: string]: number;
+    static [s: number]: 42
+}
+
+C["foo"] = 1
+C.bar = 2;
+const foo = C["foo"]
+C[42] = 42
+C[2] = 2;
+const bar = C[42] 

tests/cases/conformance/classes/staticIndexSignature/staticIndexSignature2.ts

@@ -0,0 +1,11 @@
+class C {
+    static readonly [s: string]: number;
+    static readonly [s: number]: 42
+}
+
+C["foo"] = 1
+C.bar = 2;
+const foo = C["foo"]
+C[42] = 42
+C[2] = 2;
+const bar = C[42] 

tests/cases/conformance/classes/staticIndexSignature/staticIndexSignature3.ts

@@ -0,0 +1,28 @@
+// @strict: true
+
+class B {
+    static readonly [s: string]: number;
+    static readonly [s: number]: 42 | 233
+}
+
+class D extends B {
+    static readonly [s: string]: number
+}
+
+class ED extends D {
+    static readonly [s: string]: boolean
+    static readonly [s: number]: 1 
+}
+
+class DD extends D {
+    static readonly [s: string]: 421
+}
+
+const a = B["f"];
+const b =  B[42];
+const c = D["f"]
+const d = D[42]
+const e = ED["f"]
+const f = ED[42]
+const g = DD["f"]
+const h = DD[42]

tests/cases/conformance/classes/staticIndexSignature/staticIndexSignature4.ts

@@ -0,0 +1,37 @@
+// @strict: true
+
+class B {
+    static readonly [s: string]: number;
+    static readonly [s: number]: 42 | 233
+}
+
+class D {
+    static [s: string]: number;
+    static [s: number]: 42 | 233
+}
+
+interface IB {
+    static [s: string]: number;
+    static [s: number]: 42 | 233;
+}
+
+declare const v: number
+declare const i: IB
+if (v === 0) {
+    B.a = D.a
+    B[2] = D[2]
+} else if (v === 1) {
+    D.a = B.a
+    D[2] = B[2]
+} else if (v === 2) {
+    B.a = i.a
+    B[2] = i[2]
+    D.a = i.a
+    D[2] = i [2]
+} else if (v === 3) {
+    i.a = B.a
+    i[2] = B[2]
+} else if (v === 4) {
+    i.a = D.a
+    i[2] = B[2]
+}

tests/cases/conformance/classes/staticIndexSignature/staticIndexSignature5.ts

@@ -0,0 +1,24 @@
+// @strict: true
+
+class B {
+    static readonly [s: string]: number;
+    static readonly [s: number]: 42 | 233
+}
+
+interface I {
+    static readonly [s: string]: number;
+    static readonly [s: number]: 42 | 233
+}
+
+type TA = (typeof B)["foo"]
+type TB = (typeof B)[42]
+
+type TC = (typeof B)[string]
+type TD = (typeof B)[number]
+
+type TE = keyof typeof B;
+
+type TF = Pick<typeof B, number>
+type TFI = Pick<I, number>
+type TG = Omit<typeof B, number>
+type TGI = Omit<I, number>

tests/cases/conformance/classes/staticIndexSignature/staticIndexSignature6.ts

@@ -0,0 +1,19 @@
+// @strict: true
+
+function foo () {
+    return class<T> {
+        static [s: string]: number
+        static [s: number]: 42
+
+        foo(v: T) { return v }
+    }
+}
+
+const C = foo()
+C.a;
+C.a = 1;
+C[2];
+C[2] = 42;
+
+const c = new C<number>();
+c.foo(1);

tests/cases/conformance/classes/staticIndexSignature/staticIndexSignature7.ts

@@ -0,0 +1,9 @@
+// @strict: true
+class X {
+    static [index: string]: string;
+    static x = 12; // Should error, incompatible with index signature
+}
+class Y {
+    static [index: string]: string;
+    static foo() {} // should error, incompatible with index signature
+}