Detect declarations deprecated with a doc comment

[Vexu]

I already get a compile error when using declarations deprecated with @compileError, seeing the ones only deprecated with doc comments is much more useful.

On a related note, why aren't the deprecated identifiers rendered with a strikethrough?

/// Deprecated
const foo = 123;
const bar = @compileError("foo");
comptime {
    foo;
    bar;
}

vs

/**
 * @deprecated test
 */
const foo = 1;
foo

[Techatrix]

On a related note, why aren't the deprecated identifiers rendered with a strikethrough?

I believe that VS Code (and possibly other editors) use diagnostics decide whether to render strikethrough symbols using DiagnosticTag::Deprecated. To use semantic tokens, the following change was necessary:

  "editor.semanticTokenColorCustomizations": {
    "rules": {
      "*.deprecated": {
        "strikethrough": true
      }
    }
  }

In the javascript example, you should see a 'foo' is deprecated. message when hovering over foo.

---

Since ziglang/zig#22822 has been accepted, I am not sure we should support signifying deprecation through comments and instead rely on @deprecated. The DiagnosticTag::Deprecated should be added to error messages if they contain the word "deprecated" at the start or match the output produced by @deprecated.