Narrow caught exceptions

The update from TypeScript 3.9.7 to 4.5.4 brings increased type strictness (introduced in 4.4). Previously, exceptions
were used in some catch blocks based on an assumption of their type. But exceptions can have any type and that now
results in errors (TS2345, TS2571). This is fixed by narrowing the exceptions to the expected type before using them as
such.

Author: per1234

src/installer.ts

@@ -67,7 +67,9 @@ async function downloadRelease(version: string): Promise<string> {
     const token: string = core.getInput("token", { required: true });
     downloadPath = await tc.downloadTool(downloadUrl, undefined, token);
   } catch (error) {
-    core.debug(error);
+    if (typeof error === "string" || error instanceof Error) {
+      core.debug(error.toString());
+    }
     throw `Failed to download version ${version}: ${error}`;
   }
 

src/main.ts

@@ -58,7 +58,11 @@ async function run() {
 
     await exec.exec(toolPath, execArgs, options);
   } catch (error) {
-    core.setFailed(error.message);
+    if (error instanceof Error) {
+      core.setFailed(error.message);
+    } else {
+      throw error;
+    }
   }
 }