lspbench: probe diagnostics and format against a BROKEN fixture

Plus docs/lsp-evaluation.md: the three backends measured head to head.

1 files changed, 25 insertions, 0 deletions

diff --git a/test/lspfixture/broken.zig b/test/lspfixture/broken.zig
new file mode 100644
index 00000000..22c86c9b
--- /dev/null
+++ b/test/lspfixture/broken.zig
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+//! A deliberately defective file, for the lspbench diagnostics and format
+//! probes. It is NOT built and NOT imported by anything — `zig build` never
+//! sees it, and the snapshot corpus never opens it.
+//!
+//! Why it exists: on a clean, already-formatted corpus the CORRECT answer to
+//! "what is wrong with this file" is nothing, which the harness cannot tell
+//! apart from a backend that has no diagnostics at all. That blind spot
+//! rewards a backend for emitting a filler row and punishes one for being
+//! honest, so the probes point here instead, where there is something real to
+//! find:
+//!
+//!   - `unused_local` is a SEMANTIC error. A tokenizer cannot see it; it takes
+//!     a compiler front end (AstGen/ZIR, or `zig ast-check`).
+//!   - the spacing in `badly_spaced` is a FORMATTING difference, which only a
+//!     formatter reports.
+//!
+//! Keep both. Removing either silently turns a probe back into a blind one.
+pub fn hasUnusedLocal() u32 {
+    const unused_local = 41;
+    return 7;
+}
+
+pub fn badly_spaced (  a : u32 , b : u32 ) u32 {
+    return a+b;
+}