From 07a5b212dd38c04a25249c7b97acb5db5969bc03 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Mon, 18 Mar 2024 23:57:36 +0000
Subject: [PATCH] Accept `T` in `assert!` where `<T as Not<Output = bool>` in
 <=2021 editions

---
 compiler/rustc_builtin_macros/src/assert.rs   | 76 +++++++++++--------
 compiler/rustc_hir_typeck/src/demand.rs       |  2 +-
 .../issue-28308.edition2021.stderr            | 11 +++
 ....stderr => issue-28308.edition2024.stderr} |  2 +-
 tests/ui/codemap_tests/issue-28308.rs         |  7 +-
 tests/ui/issues/issue-14091-2.rs              |  2 +-
 tests/ui/issues/issue-14091-2.stderr          | 15 +++-
 tests/ui/issues/issue-14091.stderr            |  2 +
 8 files changed, 77 insertions(+), 40 deletions(-)
 create mode 100644 tests/ui/codemap_tests/issue-28308.edition2021.stderr
 rename tests/ui/codemap_tests/{issue-28308.stderr => issue-28308.edition2024.stderr} (87%)

diff --git a/compiler/rustc_builtin_macros/src/assert.rs b/compiler/rustc_builtin_macros/src/assert.rs
index 2ffa1d6305afb..3e2108413dcf4 100644
--- a/compiler/rustc_builtin_macros/src/assert.rs
+++ b/compiler/rustc_builtin_macros/src/assert.rs
@@ -11,6 +11,7 @@ use rustc_ast_pretty::pprust;
 use rustc_errors::PResult;
 use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacEager, MacroExpanderResult};
 use rustc_parse::parser::Parser;
+use rustc_span::edition::Edition;
 use rustc_span::symbol::{sym, Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
 use thin_vec::thin_vec;
@@ -172,41 +173,37 @@ fn expand_cond(cx: &ExtCtxt<'_>, parser: Parser<'_>, cond_expr: P<Expr>) -> P<Ex
     // talk about traits, we'll just state the appropriate type error.
     // `let assert_macro: bool = $expr;`
     let ident = Ident::new(sym::assert_macro, DUMMY_SP);
-    let local = P(ast::Local {
-        ty: Some(P(ast::Ty {
-            kind: ast::TyKind::Path(None, ast::Path::from_ident(Ident::new(sym::bool, DUMMY_SP))),
-            id: ast::DUMMY_NODE_ID,
-            span: DUMMY_SP,
-            tokens: None,
-        })),
-        pat: parser.mk_pat_ident(DUMMY_SP, ast::BindingAnnotation::NONE, ident),
-        kind: ast::LocalKind::Init(cond_expr),
-        id: ast::DUMMY_NODE_ID,
-        span,
-        colon_sp: None,
-        attrs: Default::default(),
-        tokens: None,
-    });
-    // `{ let assert_macro: bool = $expr; assert_macro }`
-    parser.mk_expr(
-        span,
-        ast::ExprKind::Block(
-            parser.mk_block(
-                thin_vec![
-                    parser.mk_stmt(span, ast::StmtKind::Let(local)),
-                    parser.mk_stmt(
-                        span,
-                        ast::StmtKind::Expr(parser.mk_expr(
-                            span,
-                            ast::ExprKind::Path(None, ast::Path::from_ident(ident))
-                        )),
-                    ),
-                ],
-                ast::BlockCheckMode::Default,
-                span,
+
+    let expr = if use_assert_2024(span) {
+        // `{ let assert_macro: bool = $expr; assert_macro }`
+        cond_expr
+    } else {
+        // In <=2021, we allow anything that can be negated to `bool`, not just `bool`s. We use the
+        // "double not" trick to coerce the expression to `bool`. We still assign it to a new `bool`
+        // binding so that in the case of a type that implements `Not` but doesn't return `bool`,
+        // like `i32`, we still point at the condition and not at the whole macro.
+        // `{ let assert_macro: bool = !!$expr; assert_macro }`
+        let not = |expr| parser.mk_expr(span, ast::ExprKind::Unary(ast::UnOp::Not, expr));
+        not(not(cond_expr))
+    };
+    let block = thin_vec![
+        cx.stmt_let_ty(
+            DUMMY_SP,
+            false,
+            ident,
+            Some(cx.ty_ident(span, Ident::new(sym::bool, DUMMY_SP))),
+            expr,
+        ),
+        parser.mk_stmt(
+            span,
+            ast::StmtKind::Expr(
+                parser.mk_expr(span, ast::ExprKind::Path(None, ast::Path::from_ident(ident)))
             ),
-            None,
         ),
+    ];
+    parser.mk_expr(
+        span,
+        ast::ExprKind::Block(parser.mk_block(block, ast::BlockCheckMode::Default, span), None),
     )
 }
 
@@ -214,3 +211,16 @@ fn parse_custom_message(parser: &mut Parser<'_>) -> Option<TokenStream> {
     let ts = parser.parse_tokens();
     if !ts.is_empty() { Some(ts) } else { None }
 }
+
+pub fn use_assert_2024(mut span: Span) -> bool {
+    // To determine the edition, we check the first span up the expansion
+    // stack that isn't internal.
+    loop {
+        let expn = span.ctxt().outer_expn_data();
+        if let Some(_features) = expn.allow_internal_unstable {
+            span = expn.call_site;
+            continue;
+        }
+        break expn.edition >= Edition::Edition2024;
+    }
+}
diff --git a/compiler/rustc_hir_typeck/src/demand.rs b/compiler/rustc_hir_typeck/src/demand.rs
index 1927233796b3a..09a5c15c33f0c 100644
--- a/compiler/rustc_hir_typeck/src/demand.rs
+++ b/compiler/rustc_hir_typeck/src/demand.rs
@@ -679,7 +679,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) {
         match (self.tcx.parent_hir_node(expr.hir_id), error) {
             (hir::Node::Local(hir::Local { ty: Some(ty), init: Some(init), .. }), _)
-                if init.hir_id == expr.hir_id && !ty.span.is_dummy() =>
+                if init.hir_id == expr.hir_id && !ty.span.source_equal(init.span) =>
             {
                 // Point at `let` assignment type.
                 err.span_label(ty.span, "expected due to this");
diff --git a/tests/ui/codemap_tests/issue-28308.edition2021.stderr b/tests/ui/codemap_tests/issue-28308.edition2021.stderr
new file mode 100644
index 0000000000000..6726c01907a4b
--- /dev/null
+++ b/tests/ui/codemap_tests/issue-28308.edition2021.stderr
@@ -0,0 +1,11 @@
+error[E0600]: cannot apply unary operator `!` to type `&'static str`
+  --> $DIR/issue-28308.rs:6:13
+   |
+LL |     assert!("foo");
+   |             ^^^^^ cannot apply unary operator `!`
+   |
+   = note: this error originates in the macro `assert` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0600`.
diff --git a/tests/ui/codemap_tests/issue-28308.stderr b/tests/ui/codemap_tests/issue-28308.edition2024.stderr
similarity index 87%
rename from tests/ui/codemap_tests/issue-28308.stderr
rename to tests/ui/codemap_tests/issue-28308.edition2024.stderr
index 6d7068199c188..08c1b12afe19a 100644
--- a/tests/ui/codemap_tests/issue-28308.stderr
+++ b/tests/ui/codemap_tests/issue-28308.edition2024.stderr
@@ -1,5 +1,5 @@
 error[E0308]: mismatched types
-  --> $DIR/issue-28308.rs:2:13
+  --> $DIR/issue-28308.rs:6:13
    |
 LL |     assert!("foo");
    |             ^^^^^ expected `bool`, found `&str`
diff --git a/tests/ui/codemap_tests/issue-28308.rs b/tests/ui/codemap_tests/issue-28308.rs
index 3553c66ae16c4..49c330210051e 100644
--- a/tests/ui/codemap_tests/issue-28308.rs
+++ b/tests/ui/codemap_tests/issue-28308.rs
@@ -1,4 +1,9 @@
+//@revisions: edition2024 edition2021
+//@[edition2024] edition:2024
+//@[edition2024] compile-flags: -Z unstable-options
+//@[edition2021] edition:2021
 fn main() {
     assert!("foo");
-    //~^ ERROR mismatched types
+    //[edition2024]~^ ERROR mismatched types
+    //[edition2021]~^^ ERROR cannot apply unary operator `!` to type `&'static str`
 }
diff --git a/tests/ui/issues/issue-14091-2.rs b/tests/ui/issues/issue-14091-2.rs
index 23163b8cf481a..e2f6b18337266 100644
--- a/tests/ui/issues/issue-14091-2.rs
+++ b/tests/ui/issues/issue-14091-2.rs
@@ -13,5 +13,5 @@ fn main() {
     let x = BytePos(1);
 
     assert!(x, x);
-    //~^ ERROR mismatched types
+    //~^ ERROR cannot apply unary operator `!` to type `BytePos`
 }
diff --git a/tests/ui/issues/issue-14091-2.stderr b/tests/ui/issues/issue-14091-2.stderr
index a7b6cdb682649..55d50ee5a54a8 100644
--- a/tests/ui/issues/issue-14091-2.stderr
+++ b/tests/ui/issues/issue-14091-2.stderr
@@ -1,9 +1,18 @@
-error[E0308]: mismatched types
+error[E0600]: cannot apply unary operator `!` to type `BytePos`
   --> $DIR/issue-14091-2.rs:15:13
    |
 LL |     assert!(x, x);
-   |             ^ expected `bool`, found `BytePos`
+   |             ^ cannot apply unary operator `!`
+   |
+note: an implementation of `Not` might be missing for `BytePos`
+  --> $DIR/issue-14091-2.rs:6:1
+   |
+LL | pub struct BytePos(pub u32);
+   | ^^^^^^^^^^^^^^^^^^ must implement `Not`
+note: the trait `Not` must be implemented
+  --> $SRC_DIR/core/src/ops/bit.rs:LL:COL
+   = note: this error originates in the macro `assert` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0600`.
diff --git a/tests/ui/issues/issue-14091.stderr b/tests/ui/issues/issue-14091.stderr
index b00f651fb320f..53251699eb404 100644
--- a/tests/ui/issues/issue-14091.stderr
+++ b/tests/ui/issues/issue-14091.stderr
@@ -3,6 +3,8 @@ error[E0308]: mismatched types
    |
 LL |     assert!(1,1);
    |             ^ expected `bool`, found integer
+   |
+   = note: this error originates in the macro `assert` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 1 previous error