Fix crash for destructuring under noUncheckedIndexedAccess + noLib. (#3760)

Author: DanielRosenwasser

internal/checker/flow.go

@@ -2314,6 +2314,9 @@ func (c *Checker) getTypeOfDestructuredArrayElement(t *Type, index int) *Type {
 }
 
 func (c *Checker) includeUndefinedInIndexSignature(t *Type) *Type {
+	if t == nil {
+		return nil
+	}
 	if c.compilerOptions.NoUncheckedIndexedAccess == core.TSTrue {
 		return c.getUnionType([]*Type{t, c.missingType})
 	}

testdata/baselines/reference/compiler/noLibAndNoUncheckedIndexedAccessDestructuringArray.errors.txt

@@ -0,0 +1,21 @@
+input.ts(2,6): error TS2339: Property '0' does not exist on type 'string[]'.
+
+
+==== globals.ts (0 errors) ====
+    interface Array<T> {}
+    interface Boolean {}
+    interface Function {}
+    interface CallableFunction {}
+    interface NewableFunction {}
+    interface IArguments {}
+    interface Number {}
+    interface Object {}
+    interface RegExp {}
+    interface String {}
+    
+==== input.ts (1 errors) ====
+    declare var x: string[];
+    var [a] = x;
+         ~
+!!! error TS2339: Property '0' does not exist on type 'string[]'.
+    

testdata/baselines/reference/compiler/noLibAndNoUncheckedIndexedAccessDestructuringArray.js

@@ -0,0 +1,24 @@
+//// [tests/cases/compiler/noLibAndNoUncheckedIndexedAccessDestructuringArray.ts] ////
+
+//// [globals.ts]
+interface Array<T> {}
+interface Boolean {}
+interface Function {}
+interface CallableFunction {}
+interface NewableFunction {}
+interface IArguments {}
+interface Number {}
+interface Object {}
+interface RegExp {}
+interface String {}
+
+//// [input.ts]
+declare var x: string[];
+var [a] = x;
+
+
+//// [globals.js]
+"use strict";
+//// [input.js]
+"use strict";
+var [a] = x;

testdata/baselines/reference/compiler/noLibAndNoUncheckedIndexedAccessDestructuringArray.symbols

@@ -0,0 +1,42 @@
+//// [tests/cases/compiler/noLibAndNoUncheckedIndexedAccessDestructuringArray.ts] ////
+
+=== globals.ts ===
+interface Array<T> {}
+>Array : Symbol(Array, Decl(globals.ts, 0, 0))
+>T : Symbol(T, Decl(globals.ts, 0, 16))
+
+interface Boolean {}
+>Boolean : Symbol(Boolean, Decl(globals.ts, 0, 21))
+
+interface Function {}
+>Function : Symbol(Function, Decl(globals.ts, 1, 20))
+
+interface CallableFunction {}
+>CallableFunction : Symbol(CallableFunction, Decl(globals.ts, 2, 21))
+
+interface NewableFunction {}
+>NewableFunction : Symbol(NewableFunction, Decl(globals.ts, 3, 29))
+
+interface IArguments {}
+>IArguments : Symbol(IArguments, Decl(globals.ts, 4, 28))
+
+interface Number {}
+>Number : Symbol(Number, Decl(globals.ts, 5, 23))
+
+interface Object {}
+>Object : Symbol(Object, Decl(globals.ts, 6, 19))
+
+interface RegExp {}
+>RegExp : Symbol(RegExp, Decl(globals.ts, 7, 19))
+
+interface String {}
+>String : Symbol(String, Decl(globals.ts, 8, 19))
+
+=== input.ts ===
+declare var x: string[];
+>x : Symbol(x, Decl(input.ts, 0, 11))
+
+var [a] = x;
+>a : Symbol(a, Decl(input.ts, 1, 5))
+>x : Symbol(x, Decl(input.ts, 0, 11))
+

testdata/baselines/reference/compiler/noLibAndNoUncheckedIndexedAccessDestructuringArray.types

@@ -0,0 +1,23 @@
+//// [tests/cases/compiler/noLibAndNoUncheckedIndexedAccessDestructuringArray.ts] ////
+
+=== globals.ts ===
+
+interface Array<T> {}
+interface Boolean {}
+interface Function {}
+interface CallableFunction {}
+interface NewableFunction {}
+interface IArguments {}
+interface Number {}
+interface Object {}
+interface RegExp {}
+interface String {}
+
+=== input.ts ===
+declare var x: string[];
+>x : string[]
+
+var [a] = x;
+>a : any
+>x : string[]
+

testdata/tests/cases/compiler/noLibAndNoUncheckedIndexedAccessDestructuringArray.ts

@@ -0,0 +1,18 @@
+// @noUncheckedIndexedAccess: true
+// @noLib: true
+
+// @filename: globals.ts
+interface Array<T> {}
+interface Boolean {}
+interface Function {}
+interface CallableFunction {}
+interface NewableFunction {}
+interface IArguments {}
+interface Number {}
+interface Object {}
+interface RegExp {}
+interface String {}
+
+// @filename: input.ts
+declare var x: string[];
+var [a] = x;