From 825cc01f3bf136322b814152ede8fe0d4a322019 Mon Sep 17 00:00:00 2001
From: Giulio Caprino <julo134@gmail.com>
Date: Fri, 18 Sep 2020 17:40:18 +0100
Subject: [PATCH] fix(typescript): restore support for typescript 3

---
 definitelyTypedTests/package-lock.json     |  6 +++---
 definitelyTypedTests/package.json          |  6 +++---
 package-lock.json                          |  6 +++---
 package.json                               |  2 +-
 src/transformer/descriptor/tuple/tuple.ts  | 17 ++++++++++++++++-
 src/transformer/mockDefiner/mockDefiner.ts |  5 ++---
 6 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/definitelyTypedTests/package-lock.json b/definitelyTypedTests/package-lock.json
index a70d281e6..91fd186e8 100644
--- a/definitelyTypedTests/package-lock.json
+++ b/definitelyTypedTests/package-lock.json
@@ -1125,9 +1125,9 @@
       }
     },
     "typescript": {
-      "version": "4.0.2",
-      "resolved": "https://registry.npmjs.org/typescript/-/typescript-4.0.2.tgz",
-      "integrity": "sha512-e4ERvRV2wb+rRZ/IQeb3jm2VxBsirQLpQhdxplZ2MEzGvDkkMmPglecnNDfSUBivMjP93vRbngYYDQqQ/78bcQ=="
+      "version": "3.9.7",
+      "resolved": "https://registry.npmjs.org/typescript/-/typescript-3.9.7.tgz",
+      "integrity": "sha512-BLbiRkiBzAwsjut4x/dsibSTB6yWpwT5qWmC2OfuCg3GgVQCSgMs4vEctYPhsaGtd0AeuuHMkjZ2h2WG8MSzRw=="
     },
     "upath": {
       "version": "1.2.0",
diff --git a/definitelyTypedTests/package.json b/definitelyTypedTests/package.json
index 5ab470870..55c1bf937 100644
--- a/definitelyTypedTests/package.json
+++ b/definitelyTypedTests/package.json
@@ -16,10 +16,10 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
+    "cross-var": "^1.1.0",
     "dotenv": "^8.2.0",
     "ttypescript": "^1.5.10",
-    "typescript": "^4.0.2",
-    "upath": "^1.2.0",
-    "cross-var": "^1.1.0"
+    "typescript": "^3.9.7",
+    "upath": "^1.2.0"
   }
 }
diff --git a/package-lock.json b/package-lock.json
index cb51491c0..f3292930a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -14634,9 +14634,9 @@
       "dev": true
     },
     "typescript": {
-      "version": "4.0.2",
-      "resolved": "https://registry.npmjs.org/typescript/-/typescript-4.0.2.tgz",
-      "integrity": "sha512-e4ERvRV2wb+rRZ/IQeb3jm2VxBsirQLpQhdxplZ2MEzGvDkkMmPglecnNDfSUBivMjP93vRbngYYDQqQ/78bcQ==",
+      "version": "3.9.7",
+      "resolved": "https://registry.npmjs.org/typescript/-/typescript-3.9.7.tgz",
+      "integrity": "sha512-BLbiRkiBzAwsjut4x/dsibSTB6yWpwT5qWmC2OfuCg3GgVQCSgMs4vEctYPhsaGtd0AeuuHMkjZ2h2WG8MSzRw==",
       "dev": true
     },
     "uglify-js": {
diff --git a/package.json b/package.json
index 883b0d1b0..99860d676 100644
--- a/package.json
+++ b/package.json
@@ -84,7 +84,7 @@
         "ts-node": "^9.0.0",
         "tsconfig-paths": "^3.9.0",
         "ttypescript": "1.5.10",
-        "typescript": "^4.0.2",
+        "typescript": "^3.9.7",
         "webpack": "^4.44.1",
         "webpack-cli": "^3.3.12",
         "webpack-merge": "^5.1.2",
diff --git a/src/transformer/descriptor/tuple/tuple.ts b/src/transformer/descriptor/tuple/tuple.ts
index 8f1ba8d8b..4f1f4fbc1 100644
--- a/src/transformer/descriptor/tuple/tuple.ts
+++ b/src/transformer/descriptor/tuple/tuple.ts
@@ -7,6 +7,21 @@ export function GetTupleDescriptor(
   scope: Scope
 ): ts.Expression {
   return ts.createArrayLiteral(
-    node.elements.map((e: ts.TypeNode) => GetDescriptor(e, scope))
+    getDescriptorFromTypeNodes(
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      ((node as any).elementTypes as ts.NodeArray<ts.TypeNode>) ||
+        // Typescript 4 doesn't have elementTypes but it does have elements, to support both versions
+        // this casting is needed.
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        ((node as any).elements as ts.NodeArray<ts.TypeNode>),
+      scope
+    )
   );
 }
+
+function getDescriptorFromTypeNodes(
+  nodes: ts.NodeArray<ts.TypeNode>,
+  scope: Scope
+): ts.Expression[] {
+  return nodes.map((e: ts.TypeNode) => GetDescriptor(e, scope));
+}
diff --git a/src/transformer/mockDefiner/mockDefiner.ts b/src/transformer/mockDefiner/mockDefiner.ts
index f59cb17c1..38dd5fd3b 100644
--- a/src/transformer/mockDefiner/mockDefiner.ts
+++ b/src/transformer/mockDefiner/mockDefiner.ts
@@ -182,9 +182,8 @@ export class MockDefiner {
       );
     }
 
-    // NOTE: TypeScript does not support inference through has/get, but we know
-    // for a fact that the result here is a string!
-    return this._declarationCache.get(declaration) as string;
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    return this._declarationCache.get(declaration)!;
   }
 
   public registerMockFor(