Add small module-level docs

crates/ra_hir/src/from_id.rs

@@ -1,3 +1,8 @@
+//! Utility module for converting between hir_def ids and code_model wrappers.
+//!
+//! It's unclear if we need this long-term, but it's definitelly useful while we
+//! are splitting the hir.
+
 use hir_def::{AdtId, EnumVariantId, ModuleDefId};
 
 use crate::{Adt, EnumVariant, ModuleDef};

crates/ra_hir_def/src/diagnostics.rs

@@ -1,3 +1,5 @@
+//! Diagnostics produced by `hir_def`.
+
 use std::any::Any;
 
 use hir_expand::diagnostics::Diagnostic;

crates/ra_hir_def/src/test_db.rs

@@ -1,3 +1,5 @@
+//! Database used for testing `hir_def`.
+
 use std::{
     panic,
     sync::{Arc, Mutex},

xtask/tests/tidy-tests/docs.rs

@@ -36,6 +36,7 @@ fn is_hidden(entry: &DirEntry) -> bool {
 fn no_docs_comments() {
     let crates = project_root().join("crates");
     let iter = WalkDir::new(crates);
+    let mut missing_docs = Vec::new();
     for f in iter.into_iter().filter_entry(|e| !is_hidden(e)) {
         let f = f.unwrap();
         if f.file_type().is_dir() {
@@ -54,12 +55,14 @@ fn no_docs_comments() {
         let mut line = String::new();
         reader.read_line(&mut line).unwrap();
         if !line.starts_with("//!") {
+            missing_docs.push(f.path().display().to_string());
+        }
+    }
+    if !missing_docs.is_empty() {
         panic!(
-                "\nMissing docs strings\n\
-                 module: {}\n\
-                 Need add doc for module\n",
-                f.path().display()
+            "\nMissing docs strings\n\n\
+             modules:\n{}\n\n",
+            missing_docs.join("\n")
         )
     }
-    }
 }