Only apply ProceduralMasquerade hack to older versions of rental

The latest version of `rental` (v0.5.6) contains a fix that allows it to
compile without relying on the pretty-print back-compat hack.

Hopefully, there are no longer any crates relying on the affected
versions of the (much less popular) `procedural-masquerade` crate. This
should allow us to target the pretty-print back-compat hack specifically
to older versions of `rental`, and specifically mention upgrading to
`rental` v0.5.6 in the lint message.

Author: Aaron1011

compiler/rustc_expand/src/base.rs

@@ -22,7 +22,7 @@ use rustc_span::edition::Edition;
 use rustc_span::hygiene::{AstPass, ExpnData, ExpnKind, LocalExpnId};
 use rustc_span::source_map::SourceMap;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
-use rustc_span::{BytePos, FileName, Span, DUMMY_SP};
+use rustc_span::{BytePos, FileName, RealFileName, Span, DUMMY_SP};
 use smallvec::{smallvec, SmallVec};
 
 use std::default::Default;
@@ -1423,16 +1423,40 @@ fn pretty_printing_compatibility_hack(item: &Item, sess: &ParseSess) -> bool {
         if let ast::ItemKind::Enum(enum_def, _) = &item.kind {
             if let [variant] = &*enum_def.variants {
                 if variant.ident.name == sym::Input {
-                    sess.buffer_lint_with_diagnostic(
-                        &PROC_MACRO_BACK_COMPAT,
-                        item.ident.span,
-                        ast::CRATE_NODE_ID,
-                        "using `procedural-masquerade` crate",
-                        BuiltinLintDiagnostics::ProcMacroBackCompat(
-                        "The `procedural-masquerade` crate has been unnecessary since Rust 1.30.0. \
-                        Versions of this crate below 0.1.7 will eventually stop compiling.".to_string())
-                    );
-                    return true;
+                    let filename = sess.source_map().span_to_filename(item.ident.span);
+                    if let FileName::Real(RealFileName::LocalPath(path)) = filename {
+                        if let Some(c) = path
+                            .components()
+                            .flat_map(|c| c.as_os_str().to_str())
+                            .find(|c| c.starts_with("rental") || c.starts_with("allsorts-rental"))
+                        {
+                            let crate_matches = if c.starts_with("allsorts-rental") {
+                                true
+                            } else {
+                                let mut version = c.trim_start_matches("rental-").split(".");
+                                version.next() == Some("0")
+                                    && version.next() == Some("5")
+                                    && version
+                                        .next()
+                                        .and_then(|c| c.parse::<u32>().ok())
+                                        .map_or(false, |v| v < 6)
+                            };
+
+                            if crate_matches {
+                                sess.buffer_lint_with_diagnostic(
+                                        &PROC_MACRO_BACK_COMPAT,
+                                        item.ident.span,
+                                        ast::CRATE_NODE_ID,
+                                        "using an old version of `rental`",
+                                        BuiltinLintDiagnostics::ProcMacroBackCompat(
+                                        "older versions of the `rental` crate will stop compiling in future versions of Rust; \
+                                        please update to `rental` v0.5.6, or switch to one of the `rental` alternatives".to_string()
+                                        )
+                                    );
+                                return true;
+                            }
+                        }
+                    }
                 }
             }
         }

src/test/ui/proc-macro/issue-73933-procedural-masquerade.rs

@@ -1,18 +1,11 @@
 // aux-build:test-macros.rs
+// check-pass
 
 #[macro_use]
 extern crate test_macros;
 
 #[derive(Print)]
 enum ProceduralMasqueradeDummyType {
-//~^ ERROR using
-//~| WARN this was previously
-//~| ERROR using
-//~| WARN this was previously
-//~| ERROR using
-//~| WARN this was previously
-//~| ERROR using
-//~| WARN this was previously
     Input
 }
 

src/test/ui/proc-macro/issue-73933-procedural-masquerade.stderr

@@ -1,22 +1,21 @@
-PRINT-DERIVE INPUT (DISPLAY): enum ProceduralMasqueradeDummyType { Input, }
-PRINT-DERIVE RE-COLLECTED (DISPLAY): enum ProceduralMasqueradeDummyType { Input }
+PRINT-DERIVE INPUT (DISPLAY): enum ProceduralMasqueradeDummyType { Input }
 PRINT-DERIVE INPUT (DEBUG): TokenStream [
     Ident {
         ident: "enum",
-        span: #0 bytes(86..90),
+        span: #0 bytes(100..104),
     },
     Ident {
         ident: "ProceduralMasqueradeDummyType",
-        span: #0 bytes(91..120),
+        span: #0 bytes(105..134),
     },
     Group {
         delimiter: Brace,
         stream: TokenStream [
             Ident {
                 ident: "Input",
-                span: #0 bytes(315..320),
+                span: #0 bytes(141..146),
             },
         ],
-        span: #0 bytes(121..322),
+        span: #0 bytes(135..148),
     },
 ]

src/test/ui/proc-macro/issue-73933-procedural-masquerade.stdout

@@ -0,0 +1,12 @@
+// aux-build:test-macros.rs
+// compile-flags: -Z span-debug
+// check-pass
+
+#![no_std] // Don't load unnecessary hygiene information from std
+extern crate std;
+
+#[macro_use] extern crate test_macros;
+
+include!("pretty-print-hack/rental-0.5.6/src/lib.rs");
+
+fn main() {}

src/test/ui/proc-macro/pretty-print-hack-hide.rs

@@ -0,0 +1,21 @@
+PRINT-DERIVE INPUT (DISPLAY): enum ProceduralMasqueradeDummyType { Input }
+PRINT-DERIVE INPUT (DEBUG): TokenStream [
+    Ident {
+        ident: "enum",
+        span: $DIR/pretty-print-hack/rental-0.5.6/src/lib.rs:4:1: 4:5 (#0),
+    },
+    Ident {
+        ident: "ProceduralMasqueradeDummyType",
+        span: $DIR/pretty-print-hack/rental-0.5.6/src/lib.rs:4:6: 4:35 (#0),
+    },
+    Group {
+        delimiter: Brace,
+        stream: TokenStream [
+            Ident {
+                ident: "Input",
+                span: $DIR/pretty-print-hack/rental-0.5.6/src/lib.rs:13:5: 13:10 (#0),
+            },
+        ],
+        span: $DIR/pretty-print-hack/rental-0.5.6/src/lib.rs:4:36: 14:2 (#0),
+    },
+]

src/test/ui/proc-macro/pretty-print-hack-hide.stdout

@@ -0,0 +1,17 @@
+// aux-build:test-macros.rs
+// compile-flags: -Z span-debug
+
+#![no_std] // Don't load unnecessary hygiene information from std
+extern crate std;
+
+#[macro_use] extern crate test_macros;
+
+mod first {
+    include!("pretty-print-hack/allsorts-rental-0.5.6/src/lib.rs");
+}
+
+mod second {
+    include!("pretty-print-hack/rental-0.5.5/src/lib.rs");
+}
+
+fn main() {}