better type docs for validation message (#150923)

src/vscode-dts/vscode.d.ts

@@ -2050,8 +2050,8 @@ declare module 'vscode' {
 		 * to the user.
 		 *
 		 * @param value The current value of the input box.
-		 * @return A human-readable string which is presented as diagnostic message.
-		 * Return `undefined`, `null`, or the empty string when 'value' is valid.
+		 * @return Either a human-readable string which is presented as an error message or an {@link InputBoxValidationMessage}
+		 *  which can provide a specific message severity. Return `undefined`, `null`, or the empty string when 'value' is valid.
 		 */
 		validateInput?(value: string): string | InputBoxValidationMessage | undefined | null |
 			Thenable<string | InputBoxValidationMessage | undefined | null>;
@@ -11125,6 +11125,8 @@ declare module 'vscode' {
 
 		/**
 		 * An optional validation message indicating a problem with the current input value.
+		 * By returning a string, the InputBox will use a default {@link InputBoxValidationSeverity} of Error.
+		 * Returning undefined clears the validation message.
 		 */
 		validationMessage: string | InputBoxValidationMessage | undefined;
 	}