From cc0bd32be216d273a835a3c212207138d92e0081 Mon Sep 17 00:00:00 2001
From: Jack Firth <jackhfirth@gmail.com>
Date: Sat, 14 Sep 2024 00:50:00 -0700
Subject: [PATCH] Refactor nested let bindings in one pass (#289)

Closes #284.
---
 .../let-binding-suggestions-nesting-test.rkt  | 60 +++++++++++++++++++
 .../private/let-binding.rkt                   | 42 +++++++++----
 2 files changed, 91 insertions(+), 11 deletions(-)
 create mode 100644 default-recommendations/let-binding-suggestions-nesting-test.rkt

diff --git a/default-recommendations/let-binding-suggestions-nesting-test.rkt b/default-recommendations/let-binding-suggestions-nesting-test.rkt
new file mode 100644
index 0000000..97f2fbd
--- /dev/null
+++ b/default-recommendations/let-binding-suggestions-nesting-test.rkt
@@ -0,0 +1,60 @@
+#lang resyntax/testing/refactoring-test
+
+
+require: resyntax/default-recommendations let-binding-suggestions
+
+
+header:
+- #lang racket/base
+
+
+test: "nested let bindings"
+------------------------------
+(define (f)
+  (let ([x 1])
+    (let ([y 1])
+      (let ([z 1])
+        1))))
+------------------------------
+------------------------------
+(define (f)
+  (define x 1)
+  (define y 1)
+  (define z 1)
+  1)
+------------------------------
+
+
+test: "nested let bindings with interleaved expressions"
+------------------------------
+(define (f)
+  (let ([x 1])
+    (displayln "foo")
+    (let ([y 1])
+      (displayln "bar")
+      (let ([z 1])
+        1))))
+------------------------------
+------------------------------
+(define (f)
+  (define x 1)
+  (displayln "foo")
+  (define y 1)
+  (displayln "bar")
+  (define z 1)
+  1)
+------------------------------
+
+
+test: "nested conflicting let bindings only partially refactorable"
+------------------------------
+(define (f)
+  (let ([x 1])
+    (let ([x 2])
+      1)))
+------------------------------
+------------------------------
+(define (f)
+  (define x 1)
+  (let ([x 2]) 1))
+------------------------------
diff --git a/default-recommendations/private/let-binding.rkt b/default-recommendations/private/let-binding.rkt
index c36c956..b4cb902 100644
--- a/default-recommendations/private/let-binding.rkt
+++ b/default-recommendations/private/let-binding.rkt
@@ -27,24 +27,44 @@
 
 
 (define-splicing-syntax-class body-with-refactorable-let-expression
-  #:attributes ([refactored 1])
+  #:attributes ([refactored 1] [id 1])
   (pattern
     (~seq leading-body ... let-expression:refactorable-let-expression)
-    #:with (refactored ...) #'(leading-body ... (~@ let-expression.refactored ...))))
+    #:with (refactored ...) #'(leading-body ... (~@ let-expression.refactored ...))
+    #:with (id ...) (attribute let-expression.id)))
 
 
 (define-syntax-class refactorable-let-expression
-  #:attributes ([refactored 1])
-  #:literals (let let-values let* let*-values)
-  (pattern
-    (~or ((~or let let-values) ~! bindings:binding-group body ...+)
-         ((~or let* let*-values) ~! (~var bindings (binding-group #:nested? #true)) body ...+))
-    #:when (for/and ([id (attribute bindings.id)])
+  #:attributes ([refactored 1] [id 1])
+  (pattern (header:let-header body:let-body)
+    #:with (id ...) (append (attribute header.id) (attribute body.id))
+    #:when (for/and ([id (attribute id)])
              (not (identifier-has-exact-binding-in-context? id this-syntax)))
-    #:when (for/and ([id (attribute bindings.id)])
-             (identifier-binding-unchanged-in-context? id (first (attribute body))))
+    #:when (not (check-duplicate-identifier
+                 (for/list ([id (attribute id)])
+                   (identifier-in-context id this-syntax))))
+    #:when (for/and ([id (attribute header.id)])
+             (identifier-binding-unchanged-in-context? id (attribute body.first-body)))
     #:with (refactored ...)
-    #`(~splicing-replacement (bindings.definition ... body ...) #:original #,this-syntax)))
+    #`(~splicing-replacement (header.definition ... body.refactored ...) #:original #,this-syntax)))
+
+
+(define-splicing-syntax-class let-body
+  #:attributes (first-body [refactored 1] [id 1])
+  (pattern :body-with-refactorable-let-expression
+    #:with first-body (first (attribute refactored)))
+  (pattern (~seq first-body body ...)
+    #:with (refactored ...) this-syntax
+    #:with (id ...) '()))
+  
+
+(define-splicing-syntax-class let-header
+  #:attributes ([id 1] [definition 1])
+  #:literals (let let-values let* let*-values)
+  (pattern (~seq (~or let let-values) ~! :binding-group))
+  (pattern (~seq (~or let* let*-values) ~! (~var bindings (binding-group #:nested? #true)))
+    #:attr [id 1] (attribute bindings.id)
+    #:attr [definition 1] (attribute bindings.definition)))
 
 
 (define-syntax-class binding-clause