Vary E996 message by type

Author: J-Fields

src/cmd_line/commands/let.ts

@@ -177,9 +177,21 @@ export class LetCommand extends ExCommand {
       if (this.args.lock) {
         if (this.args.operation !== '=') {
           throw VimError.CannotModifyExistingVariable();
-        } else if (variable.type !== 'variable') {
-          // TODO: this error message should vary by type
-          throw VimError.CannotLockARegister();
+        }
+        if (variable.type !== 'variable') {
+          if (variable.type === 'register') {
+            throw VimError.CannotLock('a register');
+          }
+          if (variable.type === 'option') {
+            throw VimError.CannotLock('an option');
+          }
+          if (variable.type === 'env_variable') {
+            throw VimError.CannotLock('an environment variable');
+          }
+          if (variable.type === 'slice') {
+            throw VimError.CannotLock('a range');
+          }
+          throw VimError.CannotLock('a list or dict');
         }
       }
 

src/error.ts

@@ -89,7 +89,7 @@ export enum ErrorCode {
   CanOnlyCompareBlobWithBlob = 977,
   InvalidOperationForBlob = 978,
   CannotModifyExistingVariable = 995,
-  CannotLockARegister = 996,
+  CannotLock = 996,
   ListRequiredForArgument = 1211,
 }
 
@@ -437,8 +437,10 @@ export class VimError extends Error {
   static CannotModifyExistingVariable(): VimError {
     return new VimError(ErrorCode.CannotModifyExistingVariable, 'Cannot modify existing variable');
   }
-  static CannotLockARegister(): VimError {
-    return new VimError(ErrorCode.CannotLockARegister, 'Cannot lock a register');
+  static CannotLock(
+    what: 'a range' | 'an option' | 'a list or dict' | 'an environment variable' | 'a register',
+  ): VimError {
+    return new VimError(ErrorCode.CannotLock, `Cannot lock ${what}`);
   }
   static ListRequiredForArgument(idx: number): VimError {
     return new VimError(ErrorCode.ListRequiredForArgument, `List required for argument ${idx}`);