Auto merge of #15081 - adenine-dev:master, r=HKalbasi

Feature: Add a memory layout viewer

**Motivation**: rustc by default doesn't enforce a particular memory layout, however it can be useful to see what it is doing under the hood, or if using a particular repr ensure it is behaving how you want it to. This command provides a way to visually explore memory layouts of structures.

**Example**:
this structure:
```rust
struct X {
    x: i32,
    y: u8,
    z: Vec<bool>,
    w: usize,
}
```
produces this output:
<img width="692" alt="image" src="https://github.com/rust-lang/rust-analyzer/assets/22418744/e0312233-18a7-4bb9-ae5b-7b52fcff158a">

**Work yet to be done**:
- tests (see below)
- html is mildly janky (see below)
- enums and unions are viewed flatly, how should they be represented?
- should niches be marked somehow?

This was written for my own use, and the jank is fine for me, but in its current state it is probably not ready to merge mostly because it is missing tests, and also because the code quality is not great. However, before I spend time fixing those things idk if this is even something wanted, if it is I am happy to clean it up, if not that's cool too.

Author: bors

crates/ide-db/src/helpers.rs

@@ -9,7 +9,10 @@ use syntax::{
     AstToken, SyntaxKind, SyntaxToken, TokenAtOffset,
 };
 
-use crate::{defs::Definition, generated, RootDatabase};
+use crate::{
+    defs::{Definition, IdentClass},
+    generated, RootDatabase,
+};
 
 pub fn item_name(db: &RootDatabase, item: ItemInNs) -> Option<Name> {
     match item {
@@ -109,3 +112,16 @@ pub fn is_editable_crate(krate: Crate, db: &RootDatabase) -> bool {
     let source_root_id = db.file_source_root(root_file);
     !db.source_root(source_root_id).is_library
 }
+
+pub fn get_definition(
+    sema: &Semantics<'_, RootDatabase>,
+    token: SyntaxToken,
+) -> Option<Definition> {
+    for token in sema.descend_into_macros(token) {
+        let def = IdentClass::classify_token(sema, &token).map(IdentClass::definitions_no_ops);
+        if let Some(&[x]) = def.as_deref() {
+            return Some(x);
+        }
+    }
+    None
+}

crates/ide/src/lib.rs

@@ -60,6 +60,7 @@ mod interpret_function;
 mod view_item_tree;
 mod shuffle_crate_graph;
 mod fetch_crates;
+mod view_memory_layout;
 
 use std::ffi::OsStr;
 
@@ -74,6 +75,7 @@ use ide_db::{
 };
 use syntax::SourceFile;
 use triomphe::Arc;
+use view_memory_layout::{view_memory_layout, RecursiveMemoryLayout};
 
 use crate::navigation_target::{ToNav, TryToNav};
 
@@ -724,6 +726,13 @@ impl Analysis {
         self.with_db(|db| move_item::move_item(db, range, direction))
     }
 
+    pub fn get_recursive_memory_layout(
+        &self,
+        position: FilePosition,
+    ) -> Cancellable<Option<RecursiveMemoryLayout>> {
+        self.with_db(|db| view_memory_layout(db, position))
+    }
+
     /// Performs an operation on the database that may be canceled.
     ///
     /// rust-analyzer needs to be able to answer semantic questions about the

crates/ide/src/static_index.rs

@@ -3,13 +3,14 @@
 
 use std::collections::HashMap;
 
-use hir::{db::HirDatabase, Crate, Module, Semantics};
+use hir::{db::HirDatabase, Crate, Module};
+use ide_db::helpers::get_definition;
 use ide_db::{
     base_db::{FileId, FileRange, SourceDatabaseExt},
-    defs::{Definition, IdentClass},
+    defs::Definition,
     FxHashSet, RootDatabase,
 };
-use syntax::{AstNode, SyntaxKind::*, SyntaxToken, TextRange, T};
+use syntax::{AstNode, SyntaxKind::*, TextRange, T};
 
 use crate::{
     hover::hover_for_definition,
@@ -214,16 +215,6 @@ impl StaticIndex<'_> {
     }
 }
 
-fn get_definition(sema: &Semantics<'_, RootDatabase>, token: SyntaxToken) -> Option<Definition> {
-    for token in sema.descend_into_macros(token) {
-        let def = IdentClass::classify_token(sema, &token).map(IdentClass::definitions_no_ops);
-        if let Some(&[it]) = def.as_deref() {
-            return Some(it);
-        }
-    }
-    None
-}
-
 #[cfg(test)]
 mod tests {
     use crate::{fixture, StaticIndex};