Auto merge of #14232 - HKalbasi:mir, r=Veykril

MIR episode 2

This PR adds:
1. `need-mut` and `unused-mut` diagnostics
2. `View mir` command which shows MIR for the body under cursor, useful for debugging
3. MIR lowering for or-patterns and for-loops

1 files changed, 12 insertions, 1 deletions

diff --git a/docs/dev/lsp-extensions.md b/docs/dev/lsp-extensions.md
index c3623a5cc46..de142203208 100644
--- a/docs/dev/lsp-extensions.md
+++ b/docs/dev/lsp-extensions.md
@@ -1,5 +1,5 @@
 <!---
-lsp_ext.rs hash: d87477896dfe41d4
+lsp_ext.rs hash: 37f31ae648632897
 
 If you need to change the above hash to make the test pass, please check if you
 need to adjust this doc as well and ping this issue:
@@ -527,6 +527,17 @@ Primarily for debugging, but very useful for all people working on rust-analyzer
 Returns a textual representation of the HIR of the function containing the cursor.
 For debugging or when working on rust-analyzer itself.
 
+## View Mir
+
+**Method:** `rust-analyzer/viewMir`
+
+**Request:** `TextDocumentPositionParams`
+
+**Response:** `string`
+
+Returns a textual representation of the MIR of the function containing the cursor.
+For debugging or when working on rust-analyzer itself.
+
 ## View File Text
 
 **Method:** `rust-analyzer/viewFileText`