From 6d7294a00c3f831ed7d60a530911bff67f4e54ba Mon Sep 17 00:00:00 2001
From: Aaron Hill <aa1ronham@gmail.com>
Date: Sun, 21 Mar 2021 00:17:19 -0400
Subject: [PATCH] Perform 'deep recollection' in test helper macros

Currently, the print helper macro performs 'recollection' by doing
`token_stream.into_iter().collect()`. However, this will not affect
nonterminals that occur nested inside delimited groups, since the
wrapping delimited group will be left untouched.

This commit adds 'deep recollection', which recursively recollects every
delimited group in the token stream. As with normal recollection, we
only print out something if deep recollection results in a different
stringified token stream.

This is useful for catching bugs where we update the AST of a
nonterminal (which affects pretty-printing), but do not update the
attatched `TokenStream`
---
 .../ui/proc-macro/auxiliary/test-macros.rs    | 33 ++++++++++++++++++-
 .../issue-78675-captured-inner-attrs.stdout   |  1 +
 src/test/ui/proc-macro/nodelim-groups.stdout  |  1 +
 3 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/src/test/ui/proc-macro/auxiliary/test-macros.rs b/src/test/ui/proc-macro/auxiliary/test-macros.rs
index 1a500361640..7a46aee462b 100644
--- a/src/test/ui/proc-macro/auxiliary/test-macros.rs
+++ b/src/test/ui/proc-macro/auxiliary/test-macros.rs
@@ -83,21 +83,52 @@ fn print_helper(input: TokenStream, kind: &str) -> TokenStream {
     print_helper_ext(input, kind, true)
 }
 
+fn deep_recollect(input: TokenStream) -> TokenStream {
+    input.into_iter().map(|tree| {
+        match tree {
+            TokenTree::Group(group) => {
+                let inner = deep_recollect(group.stream());
+                let mut new_group = TokenTree::Group(
+                    proc_macro::Group::new(group.delimiter(), inner)
+                );
+                new_group.set_span(group.span());
+                new_group
+            }
+            _ => tree,
+        }
+    }).collect()
+}
+
 fn print_helper_ext(input: TokenStream, kind: &str, debug: bool) -> TokenStream {
     let input_display = format!("{}", input);
     let input_debug = format!("{:#?}", input);
-    let recollected = input.into_iter().collect();
+    let recollected = input.clone().into_iter().collect();
     let recollected_display = format!("{}", recollected);
     let recollected_debug = format!("{:#?}", recollected);
+
+    let deep_recollected = deep_recollect(input);
+    let deep_recollected_display = format!("{}", deep_recollected);
+    let deep_recollected_debug = format!("{:#?}", deep_recollected);
+
+
+
     println!("PRINT-{} INPUT (DISPLAY): {}", kind, input_display);
     if recollected_display != input_display {
         println!("PRINT-{} RE-COLLECTED (DISPLAY): {}", kind, recollected_display);
     }
+
+    if deep_recollected_display != recollected_display {
+        println!("PRINT-{} DEEP-RE-COLLECTED (DISPLAY): {}", kind, deep_recollected_display);
+    }
+
     if debug {
         println!("PRINT-{} INPUT (DEBUG): {}", kind, input_debug);
         if recollected_debug != input_debug {
             println!("PRINT-{} RE-COLLECTED (DEBUG): {}", kind, recollected_debug);
         }
+        if deep_recollected_debug != recollected_debug {
+            println!("PRINT-{} DEEP-RE-COLLETED (DEBUG): {}", kind, deep_recollected_debug);
+        }
     }
     recollected
 }
diff --git a/src/test/ui/proc-macro/issue-78675-captured-inner-attrs.stdout b/src/test/ui/proc-macro/issue-78675-captured-inner-attrs.stdout
index 40da5aa93bf..9b467a5970b 100644
--- a/src/test/ui/proc-macro/issue-78675-captured-inner-attrs.stdout
+++ b/src/test/ui/proc-macro/issue-78675-captured-inner-attrs.stdout
@@ -1,6 +1,7 @@
 PRINT-BANG INPUT (DISPLAY): foo ! { #[fake_attr] mod bar {
     #![doc = r" Foo"]
 } }
+PRINT-BANG DEEP-RE-COLLECTED (DISPLAY): foo ! { #[fake_attr] mod bar { # ! [doc = r" Foo"] } }
 PRINT-BANG INPUT (DEBUG): TokenStream [
     Ident {
         ident: "foo",
diff --git a/src/test/ui/proc-macro/nodelim-groups.stdout b/src/test/ui/proc-macro/nodelim-groups.stdout
index 6b410f0bfb7..4ffe3f35e8e 100644
--- a/src/test/ui/proc-macro/nodelim-groups.stdout
+++ b/src/test/ui/proc-macro/nodelim-groups.stdout
@@ -71,6 +71,7 @@ PRINT-BANG INPUT (DEBUG): TokenStream [
     },
 ]
 PRINT-BANG INPUT (DISPLAY): "hi" "hello".len() + "world".len() (1 + 1)
+PRINT-BANG DEEP-RE-COLLECTED (DISPLAY): "hi" "hello" . len() + "world" . len() (1 + 1)
 PRINT-BANG INPUT (DEBUG): TokenStream [
     Literal {
         kind: Str,