Move check for module kind is ES2015 into grammar check; Use checkNonNullExpression and add tests

src/compiler/checker.ts

@@ -15580,12 +15580,8 @@ namespace ts {
                 return createPromiseReturnType(node, anyType);
             }
 
-            if (modulekind === ModuleKind.ES2015) {
-                grammarErrorOnNode(node, Diagnostics.Dynamic_import_cannot_be_used_when_targeting_ECMAScript_2015_modules);
-            }
-
             const specifier = node.arguments[0];
-            const specifierType = checkExpression(specifier);
+            const specifierType = checkNonNullExpression(specifier);
             if (!isTypeAssignableTo(specifierType, stringType)) {
                 error(specifier, Diagnostics.Dynamic_import_s_specifier_must_be_of_type_string_but_here_has_type_0, typeToString(specifierType));
             }
@@ -24081,6 +24077,10 @@ namespace ts {
             if (isSpreadExpression(arguments[0])) {
                 return grammarErrorOnNode(arguments[0], Diagnostics.Specifier_of_dynamic_import_cannot_be_spread_element);
             }
+
+            if (modulekind === ModuleKind.ES2015) {
+                grammarErrorOnNode(node, Diagnostics.Dynamic_import_cannot_be_used_when_targeting_ECMAScript_2015_modules);
+            }
         }
     }
 }

tests/baselines/reference/importCallExpression5ES2018.errors.txt

@@ -0,0 +1,31 @@
+tests/cases/conformance/es2018/dynamicImport/2.ts(3,23): error TS2532: Object is possibly 'undefined'.
+tests/cases/conformance/es2018/dynamicImport/2.ts(4,24): error TS2532: Object is possibly 'undefined'.
+tests/cases/conformance/es2018/dynamicImport/2.ts(5,24): error TS2531: Object is possibly 'null'.
+tests/cases/conformance/es2018/dynamicImport/2.ts(6,24): error TS2531: Object is possibly 'null'.
+
+
+==== tests/cases/conformance/es2018/dynamicImport/0.ts (0 errors) ====
+    export class B {
+        print() { return "I am B"}
+    }
+    
+    export function foo() { return "foo" }
+    
+==== tests/cases/conformance/es2018/dynamicImport/1.ts (0 errors) ====
+    export function backup() { return "backup"; }
+    
+==== tests/cases/conformance/es2018/dynamicImport/2.ts (4 errors) ====
+    declare function bar(): boolean;
+    const specify = bar() ? "./0" : undefined;
+    let myModule = import(specify);
+                          ~~~~~~~
+!!! error TS2532: Object is possibly 'undefined'.
+    let myModule1 = import(undefined);
+                           ~~~~~~~~~
+!!! error TS2532: Object is possibly 'undefined'.
+    let myModule2 = import(bar() ? "./1" : null);
+                           ~~~~~~~~~~~~~~~~~~~~
+!!! error TS2531: Object is possibly 'null'.
+    let myModule3 = import(null);
+                           ~~~~
+!!! error TS2531: Object is possibly 'null'.

tests/baselines/reference/importCallExpression5ES2018.js

@@ -0,0 +1,33 @@
+//// [tests/cases/conformance/es2018/dynamicImport/importCallExpression5ES2018.ts] ////
+
+//// [0.ts]
+export class B {
+    print() { return "I am B"}
+}
+
+export function foo() { return "foo" }
+
+//// [1.ts]
+export function backup() { return "backup"; }
+
+//// [2.ts]
+declare function bar(): boolean;
+const specify = bar() ? "./0" : undefined;
+let myModule = import(specify);
+let myModule1 = import(undefined);
+let myModule2 = import(bar() ? "./1" : null);
+let myModule3 = import(null);
+
+//// [0.js]
+export class B {
+    print() { return "I am B"; }
+}
+export function foo() { return "foo"; }
+//// [1.js]
+export function backup() { return "backup"; }
+//// [2.js]
+const specify = bar() ? "./0" : undefined;
+let myModule = import(specify);
+let myModule1 = import(undefined);
+let myModule2 = import(bar() ? "./1" : null);
+let myModule3 = import(null);

tests/baselines/reference/importCallExpression6ES2018.errors.txt

@@ -0,0 +1,25 @@
+tests/cases/conformance/es2018/dynamicImport/2.ts(4,24): error TS2532: Object is possibly 'undefined'.
+tests/cases/conformance/es2018/dynamicImport/2.ts(6,24): error TS2531: Object is possibly 'null'.
+
+
+==== tests/cases/conformance/es2018/dynamicImport/0.ts (0 errors) ====
+    export class B {
+        print() { return "I am B"}
+    }
+    
+    export function foo() { return "foo" }
+    
+==== tests/cases/conformance/es2018/dynamicImport/1.ts (0 errors) ====
+    export function backup() { return "backup"; }
+    
+==== tests/cases/conformance/es2018/dynamicImport/2.ts (2 errors) ====
+    declare function bar(): boolean;
+    const specify = bar() ? "./0" : undefined;
+    let myModule = import(specify);
+    let myModule1 = import(undefined);
+                           ~~~~~~~~~
+!!! error TS2532: Object is possibly 'undefined'.
+    let myModule2 = import(bar() ? "./1" : null);
+    let myModule3 = import(null);
+                           ~~~~
+!!! error TS2531: Object is possibly 'null'.

tests/baselines/reference/importCallExpression6ES2018.js

@@ -0,0 +1,33 @@
+//// [tests/cases/conformance/es2018/dynamicImport/importCallExpression6ES2018.ts] ////
+
+//// [0.ts]
+export class B {
+    print() { return "I am B"}
+}
+
+export function foo() { return "foo" }
+
+//// [1.ts]
+export function backup() { return "backup"; }
+
+//// [2.ts]
+declare function bar(): boolean;
+const specify = bar() ? "./0" : undefined;
+let myModule = import(specify);
+let myModule1 = import(undefined);
+let myModule2 = import(bar() ? "./1" : null);
+let myModule3 = import(null);
+
+//// [0.js]
+export class B {
+    print() { return "I am B"; }
+}
+export function foo() { return "foo"; }
+//// [1.js]
+export function backup() { return "backup"; }
+//// [2.js]
+const specify = bar() ? "./0" : undefined;
+let myModule = import(specify);
+let myModule1 = import(undefined);
+let myModule2 = import(bar() ? "./1" : null);
+let myModule3 = import(null);

tests/cases/conformance/es2018/dynamicImport/importCallExpression5ES2018.ts

@@ -0,0 +1,20 @@
+// @module: es2018
+// @target: esnext
+// @strictNullChecks: true
+// @filename: 0.ts
+export class B {
+    print() { return "I am B"}
+}
+
+export function foo() { return "foo" }
+
+// @filename: 1.ts
+export function backup() { return "backup"; }
+
+// @filename: 2.ts
+declare function bar(): boolean;
+const specify = bar() ? "./0" : undefined;
+let myModule = import(specify);
+let myModule1 = import(undefined);
+let myModule2 = import(bar() ? "./1" : null);
+let myModule3 = import(null);

tests/cases/conformance/es2018/dynamicImport/importCallExpression6ES2018.ts

@@ -0,0 +1,19 @@
+// @module: es2018
+// @target: esnext
+// @filename: 0.ts
+export class B {
+    print() { return "I am B"}
+}
+
+export function foo() { return "foo" }
+
+// @filename: 1.ts
+export function backup() { return "backup"; }
+
+// @filename: 2.ts
+declare function bar(): boolean;
+const specify = bar() ? "./0" : undefined;
+let myModule = import(specify);
+let myModule1 = import(undefined);
+let myModule2 = import(bar() ? "./1" : null);
+let myModule3 = import(null);