[generic_assert] Avoid constant environments

compiler/rustc_ast/src/ast.rs

@@ -1715,6 +1715,7 @@ pub enum ClosureBinder {
 /// is being invoked, and the `args` are arguments passed to it.
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub struct MacCall {
+    pub is_in_const_env: bool,
     pub path: Path,
     pub args: P<DelimArgs>,
 }

compiler/rustc_ast/src/mut_visit.rs

@@ -714,7 +714,7 @@ fn walk_attribute<T: MutVisitor>(vis: &mut T, attr: &mut Attribute) {
 }
 
 fn walk_mac<T: MutVisitor>(vis: &mut T, mac: &mut MacCall) {
-    let MacCall { path, args } = mac;
+    let MacCall { is_in_const_env: _, path, args } = mac;
     vis.visit_path(path);
     visit_delim_args(vis, args);
 }

compiler/rustc_ast/src/visit.rs

@@ -1002,7 +1002,7 @@ pub fn walk_stmt<'a, V: Visitor<'a>>(visitor: &mut V, statement: &'a Stmt) -> V:
 }
 
 pub fn walk_mac<'a, V: Visitor<'a>>(visitor: &mut V, mac: &'a MacCall) -> V::Result {
-    let MacCall { path, args: _ } = mac;
+    let MacCall { is_in_const_env: _, path, args: _ } = mac;
     visitor.visit_path(path, DUMMY_NODE_ID)
 }
 

compiler/rustc_builtin_macros/src/asm.rs

@@ -814,6 +814,7 @@ fn expand_preparsed_asm(
 
 pub(super) fn expand_asm<'cx>(
     ecx: &'cx mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {
@@ -843,6 +844,7 @@ pub(super) fn expand_asm<'cx>(
 
 pub(super) fn expand_naked_asm<'cx>(
     ecx: &'cx mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {
@@ -873,6 +875,7 @@ pub(super) fn expand_naked_asm<'cx>(
 
 pub(super) fn expand_global_asm<'cx>(
     ecx: &'cx mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {

compiler/rustc_builtin_macros/src/assert.rs

@@ -17,6 +17,7 @@ use crate::errors;
 
 pub(crate) fn expand_assert<'cx>(
     cx: &'cx mut ExtCtxt<'_>,
+    is_in_const_env: bool,
     span: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {
@@ -56,6 +57,7 @@ pub(crate) fn expand_assert<'cx>(
         let then = cx.expr(
             call_site_span,
             ExprKind::MacCall(P(MacCall {
+                is_in_const_env,
                 path: panic_path(),
                 args: P(DelimArgs {
                     dspan: DelimSpan::from_single(call_site_span),
@@ -69,8 +71,8 @@ pub(crate) fn expand_assert<'cx>(
     // If `generic_assert` is enabled, generates rich captured outputs
     //
     // FIXME(c410-f3r) See https://github.com/rust-lang/rust/issues/96949
-    else if cx.ecfg.features.generic_assert() {
-        context::Context::new(cx, call_site_span).build(cond_expr, panic_path())
+    else if cx.ecfg.features.generic_assert() && !is_in_const_env {
+        context::Context::new(cx, call_site_span).build(cond_expr, is_in_const_env, panic_path())
     }
     // If `generic_assert` is not enabled, only outputs a literal "assertion failed: ..."
     // string

compiler/rustc_builtin_macros/src/assert/context.rs

@@ -71,11 +71,16 @@ impl<'cx, 'a> Context<'cx, 'a> {
     ///   }
     /// }
     /// ```
-    pub(super) fn build(mut self, mut cond_expr: P<Expr>, panic_path: Path) -> P<Expr> {
+    pub(super) fn build(
+        mut self,
+        mut cond_expr: P<Expr>,
+        is_in_const_env: bool,
+        panic_path: Path,
+    ) -> P<Expr> {
         let expr_str = pprust::expr_to_string(&cond_expr);
         self.manage_cond_expr(&mut cond_expr);
         let initial_imports = self.build_initial_imports();
-        let panic = self.build_panic(&expr_str, panic_path);
+        let panic = self.build_panic(&expr_str, is_in_const_env, panic_path);
         let cond_expr_with_unlikely = self.build_unlikely(cond_expr);
 
         let Self { best_case_captures, capture_decls, cx, local_bind_decls, span, .. } = self;
@@ -147,7 +152,7 @@ impl<'cx, 'a> Context<'cx, 'a> {
     ///     __capture0,
     ///     ...
     /// );
-    fn build_panic(&self, expr_str: &str, panic_path: Path) -> P<Expr> {
+    fn build_panic(&self, expr_str: &str, is_in_const_env: bool, panic_path: Path) -> P<Expr> {
         let escaped_expr_str = escape_to_fmt(expr_str);
         let initial = [
             TokenTree::token_joint(
@@ -179,6 +184,7 @@ impl<'cx, 'a> Context<'cx, 'a> {
         self.cx.expr(
             self.span,
             ExprKind::MacCall(P(MacCall {
+                is_in_const_env,
                 path: panic_path,
                 args: P(DelimArgs {
                     dspan: DelimSpan::from_single(self.span),

compiler/rustc_builtin_macros/src/cfg.rs

@@ -13,6 +13,7 @@ use crate::errors;
 
 pub(crate) fn expand_cfg(
     cx: &mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'static> {

compiler/rustc_builtin_macros/src/compile_error.rs

@@ -8,6 +8,7 @@ use crate::util::get_single_str_from_tts;
 
 pub(crate) fn expand_compile_error<'cx>(
     cx: &'cx mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {

compiler/rustc_builtin_macros/src/concat.rs

@@ -9,6 +9,7 @@ use crate::util::get_exprs_from_tts;
 
 pub(crate) fn expand_concat(
     cx: &mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: rustc_span::Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'static> {

compiler/rustc_builtin_macros/src/concat_bytes.rs

@@ -112,6 +112,7 @@ fn handle_array_element(
 
 pub(crate) fn expand_concat_bytes(
     cx: &mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'static> {

compiler/rustc_builtin_macros/src/concat_idents.rs

@@ -10,6 +10,7 @@ use crate::errors;
 
 pub(crate) fn expand_concat_idents<'cx>(
     cx: &'cx mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {

compiler/rustc_builtin_macros/src/edition_panic.rs

@@ -18,11 +18,12 @@ use rustc_span::symbol::sym;
 /// one we're expanding from.
 pub(crate) fn expand_panic<'cx>(
     cx: &'cx mut ExtCtxt<'_>,
+    is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {
     let mac = if use_panic_2021(sp) { sym::panic_2021 } else { sym::panic_2015 };
-    expand(mac, cx, sp, tts)
+    expand(is_in_const_env, mac, cx, sp, tts)
 }
 
 /// This expands to either
@@ -31,14 +32,16 @@ pub(crate) fn expand_panic<'cx>(
 /// depending on the edition.
 pub(crate) fn expand_unreachable<'cx>(
     cx: &'cx mut ExtCtxt<'_>,
+    is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {
     let mac = if use_panic_2021(sp) { sym::unreachable_2021 } else { sym::unreachable_2015 };
-    expand(mac, cx, sp, tts)
+    expand(is_in_const_env, mac, cx, sp, tts)
 }
 
 fn expand<'cx>(
+    is_in_const_env: bool,
     mac: rustc_span::Symbol,
     cx: &'cx ExtCtxt<'_>,
     sp: Span,
@@ -50,6 +53,7 @@ fn expand<'cx>(
         cx.expr(
             sp,
             ExprKind::MacCall(P(MacCall {
+                is_in_const_env,
                 path: Path {
                     span: sp,
                     segments: cx

compiler/rustc_builtin_macros/src/env.rs

@@ -29,6 +29,7 @@ fn lookup_env<'cx>(cx: &'cx ExtCtxt<'_>, var: Symbol) -> Result<Symbol, VarError
 
 pub(crate) fn expand_option_env<'cx>(
     cx: &'cx mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {
@@ -89,6 +90,7 @@ pub(crate) fn expand_option_env<'cx>(
 
 pub(crate) fn expand_env<'cx>(
     cx: &'cx mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {

compiler/rustc_builtin_macros/src/format.rs

@@ -1015,6 +1015,7 @@ fn expand_format_args_impl<'cx>(
 
 pub(crate) fn expand_format_args<'cx>(
     ecx: &'cx mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {
@@ -1023,6 +1024,7 @@ pub(crate) fn expand_format_args<'cx>(
 
 pub(crate) fn expand_format_args_nl<'cx>(
     ecx: &'cx mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {

compiler/rustc_builtin_macros/src/log_syntax.rs

@@ -4,6 +4,7 @@ use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacroExpanderResult
 
 pub(crate) fn expand_log_syntax<'cx>(
     _cx: &'cx mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: rustc_span::Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {

compiler/rustc_builtin_macros/src/pattern_type.rs

@@ -7,6 +7,7 @@ use rustc_span::{Span, sym};
 
 pub(crate) fn expand<'cx>(
     cx: &'cx mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {

compiler/rustc_builtin_macros/src/source_util.rs

@@ -32,6 +32,7 @@ use crate::util::{
 /// line!(): expands to the current line number
 pub(crate) fn expand_line(
     cx: &mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'static> {
@@ -47,6 +48,7 @@ pub(crate) fn expand_line(
 /* column!(): expands to the current column number */
 pub(crate) fn expand_column(
     cx: &mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'static> {
@@ -64,6 +66,7 @@ pub(crate) fn expand_column(
 /// out if we wanted.
 pub(crate) fn expand_file(
     cx: &mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'static> {
@@ -85,6 +88,7 @@ pub(crate) fn expand_file(
 
 pub(crate) fn expand_stringify(
     cx: &mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'static> {
@@ -95,6 +99,7 @@ pub(crate) fn expand_stringify(
 
 pub(crate) fn expand_mod(
     cx: &mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'static> {
@@ -111,6 +116,7 @@ pub(crate) fn expand_mod(
 /// unhygienically.
 pub(crate) fn expand_include<'cx>(
     cx: &'cx mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {
@@ -192,6 +198,7 @@ pub(crate) fn expand_include<'cx>(
 /// `include_str!`: read the given file, insert it as a literal string expr
 pub(crate) fn expand_include_str(
     cx: &mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'static> {
@@ -221,6 +228,7 @@ pub(crate) fn expand_include_str(
 
 pub(crate) fn expand_include_bytes(
     cx: &mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'static> {

compiler/rustc_builtin_macros/src/trace_macros.rs

@@ -7,6 +7,7 @@ use crate::errors;
 
 pub(crate) fn expand_trace_macros(
     cx: &mut ExtCtxt<'_>,
+    _is_in_const_env: bool,
     sp: Span,
     tt: TokenStream,
 ) -> MacroExpanderResult<'static> {

compiler/rustc_expand/src/base.rs

@@ -280,6 +280,7 @@ pub trait BangProcMacro {
     fn expand<'cx>(
         &self,
         ecx: &'cx mut ExtCtxt<'_>,
+        is_in_const_env: bool,
         span: Span,
         ts: TokenStream,
     ) -> Result<TokenStream, ErrorGuaranteed>;
@@ -292,6 +293,7 @@ where
     fn expand<'cx>(
         &self,
         _ecx: &'cx mut ExtCtxt<'_>,
+        _is_in_const_env: bool,
         _span: Span,
         ts: TokenStream,
     ) -> Result<TokenStream, ErrorGuaranteed> {
@@ -331,6 +333,7 @@ pub trait TTMacroExpander {
     fn expand<'cx>(
         &self,
         ecx: &'cx mut ExtCtxt<'_>,
+        is_in_const_env: bool,
         span: Span,
         input: TokenStream,
     ) -> MacroExpanderResult<'cx>;
@@ -339,19 +342,20 @@ pub trait TTMacroExpander {
 pub type MacroExpanderResult<'cx> = ExpandResult<Box<dyn MacResult + 'cx>, ()>;
 
 pub type MacroExpanderFn =
-    for<'cx> fn(&'cx mut ExtCtxt<'_>, Span, TokenStream) -> MacroExpanderResult<'cx>;
+    for<'cx> fn(&'cx mut ExtCtxt<'_>, bool, Span, TokenStream) -> MacroExpanderResult<'cx>;
 
 impl<F> TTMacroExpander for F
 where
-    F: for<'cx> Fn(&'cx mut ExtCtxt<'_>, Span, TokenStream) -> MacroExpanderResult<'cx>,
+    F: for<'cx> Fn(&'cx mut ExtCtxt<'_>, bool, Span, TokenStream) -> MacroExpanderResult<'cx>,
 {
     fn expand<'cx>(
         &self,
         ecx: &'cx mut ExtCtxt<'_>,
+        is_in_const_env: bool,
         span: Span,
         input: TokenStream,
     ) -> MacroExpanderResult<'cx> {
-        self(ecx, span, input)
+        self(ecx, is_in_const_env, span, input)
     }
 }
 
@@ -901,6 +905,7 @@ impl SyntaxExtension {
     pub fn dummy_bang(edition: Edition) -> SyntaxExtension {
         fn expander<'cx>(
             cx: &'cx mut ExtCtxt<'_>,
+            _is_in_const_env: bool,
             span: Span,
             _: TokenStream,
         ) -> MacroExpanderResult<'cx> {

compiler/rustc_expand/src/build.rs

@@ -53,12 +53,14 @@ impl<'a> ExtCtxt<'a> {
 
     pub fn macro_call(
         &self,
+        is_in_const_env: bool,
         span: Span,
         path: ast::Path,
         delim: ast::token::Delimiter,
         tokens: ast::tokenstream::TokenStream,
     ) -> P<ast::MacCall> {
         P(ast::MacCall {
+            is_in_const_env,
             path,
             args: P(ast::DelimArgs {
                 dspan: ast::tokenstream::DelimSpan { open: span, close: span },
@@ -435,6 +437,7 @@ impl<'a> ExtCtxt<'a> {
         self.expr_macro_call(
             span,
             self.macro_call(
+                false,
                 span,
                 self.path_global(
                     span,

compiler/rustc_expand/src/expand.rs

@@ -676,15 +676,25 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
         ExpandResult::Ready(match invoc.kind {
             InvocationKind::Bang { mac, span } => match ext {
                 SyntaxExtensionKind::Bang(expander) => {
-                    match expander.expand(self.cx, span, mac.args.tokens.clone()) {
+                    match expander.expand(
+                        self.cx,
+                        mac.is_in_const_env,
+                        span,
+                        mac.args.tokens.clone(),
+                    ) {
                         Ok(tok_result) => {
                             self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
                         }
                         Err(guar) => return ExpandResult::Ready(fragment_kind.dummy(span, guar)),
                     }
                 }
                 SyntaxExtensionKind::LegacyBang(expander) => {
-                    let tok_result = match expander.expand(self.cx, span, mac.args.tokens.clone()) {
+                    let tok_result = match expander.expand(
+                        self.cx,
+                        mac.is_in_const_env,
+                        span,
+                        mac.args.tokens.clone(),
+                    ) {
                         ExpandResult::Ready(tok_result) => tok_result,
                         ExpandResult::Retry(_) => {
                             // retry the original

compiler/rustc_expand/src/mbe/macro_rules.rs

@@ -111,6 +111,7 @@ impl TTMacroExpander for MacroRulesMacroExpander {
     fn expand<'cx>(
         &self,
         cx: &'cx mut ExtCtxt<'_>,
+        _is_in_const_env: bool,
         sp: Span,
         input: TokenStream,
     ) -> MacroExpanderResult<'cx> {
@@ -134,6 +135,7 @@ impl TTMacroExpander for DummyExpander {
     fn expand<'cx>(
         &self,
         _: &'cx mut ExtCtxt<'_>,
+        _is_in_const_env: bool,
         span: Span,
         _: TokenStream,
     ) -> ExpandResult<Box<dyn MacResult + 'cx>, ()> {

compiler/rustc_expand/src/placeholders.rs

@@ -18,6 +18,7 @@ pub(crate) fn placeholder(
 ) -> AstFragment {
     fn mac_placeholder() -> P<ast::MacCall> {
         P(ast::MacCall {
+            is_in_const_env: false,
             path: ast::Path { span: DUMMY_SP, segments: ThinVec::new(), tokens: None },
             args: P(ast::DelimArgs {
                 dspan: ast::tokenstream::DelimSpan::dummy(),

compiler/rustc_expand/src/proc_macro.rs

@@ -46,6 +46,7 @@ impl base::BangProcMacro for BangProcMacro {
     fn expand(
         &self,
         ecx: &mut ExtCtxt<'_>,
+        _is_in_const_env: bool,
         span: Span,
         input: TokenStream,
     ) -> Result<TokenStream, ErrorGuaranteed> {

compiler/rustc_parse/src/parser/expr.rs

@@ -1614,7 +1614,11 @@ impl<'a> Parser<'a> {
                 self.dcx().emit_err(errors::MacroInvocationWithQualifiedPath(path.span));
             }
             let lo = path.span;
-            let mac = P(MacCall { path, args: self.parse_delim_args()? });
+            let mac = P(MacCall {
+                is_in_const_env: self.is_in_const_env,
+                path,
+                args: self.parse_delim_args()?,
+            });
             (lo.to(self.prev_token.span), ExprKind::MacCall(mac))
         } else if self.check(&token::OpenDelim(Delimiter::Brace))
             && let Some(expr) = self.maybe_parse_struct_expr(&qself, &path)

compiler/rustc_parse/src/parser/item.rs

@@ -241,11 +241,14 @@ impl<'a> Parser<'a> {
             // CONST ITEM
             if self.token.is_keyword(kw::Impl) {
                 // recover from `const impl`, suggest `impl const`
-                self.recover_const_impl(const_span, attrs, def_())?
+                self.with_const_management(|this| {
+                    this.recover_const_impl(const_span, attrs, def_())
+                })?
             } else {
                 self.recover_const_mut(const_span);
                 self.recover_missing_kw_before_item()?;
-                let (ident, generics, ty, expr) = self.parse_const_item()?;
+                let tuple = self.with_const_management(|this| this.parse_const_item())?;
+                let (ident, generics, ty, expr) = tuple;
                 (
                     ident,
                     ItemKind::Const(Box::new(ConstItem {
@@ -486,7 +489,7 @@ impl<'a> Parser<'a> {
             Ok(args) => {
                 self.eat_semi_for_macro_if_needed(&args);
                 self.complain_if_pub_macro(vis, false);
-                Ok(MacCall { path, args })
+                Ok(MacCall { is_in_const_env: self.is_in_const_env, path, args })
             }
 
             Err(mut err) => {
@@ -2383,8 +2386,19 @@ impl<'a> Parser<'a> {
 
         let mut sig_hi = self.prev_token.span;
         // Either `;` or `{ ... }`.
-        let body =
-            self.parse_fn_body(attrs, &ident, &mut sig_hi, fn_parse_mode.req_body, fn_params_end)?;
+        let body = if let Const::Yes(_) = header.constness {
+            self.with_const_management(|this| {
+                this.parse_fn_body(
+                    attrs,
+                    &ident,
+                    &mut sig_hi,
+                    fn_parse_mode.req_body,
+                    fn_params_end,
+                )
+            })?
+        } else {
+            self.parse_fn_body(attrs, &ident, &mut sig_hi, fn_parse_mode.req_body, fn_params_end)?
+        };
         let fn_sig_span = sig_lo.to(sig_hi);
         Ok((ident, FnSig { header, decl, span: fn_sig_span }, generics, body))
     }

compiler/rustc_parse/src/parser/mod.rs

@@ -185,12 +185,14 @@ pub struct Parser<'a> {
     /// Whether the parser is allowed to do recovery.
     /// This is disabled when parsing macro arguments, see #103534
     recovery: Recovery,
+    /// If the current parsing is within a constant environment
+    is_in_const_env: bool,
 }
 
 // This type is used a lot, e.g. it's cloned when matching many declarative macro rules with nonterminals. Make sure
 // it doesn't unintentionally get bigger.
 #[cfg(target_pointer_width = "64")]
-rustc_data_structures::static_assert_size!(Parser<'_>, 288);
+rustc_data_structures::static_assert_size!(Parser<'_>, 296);
 
 /// Stores span information about a closure.
 #[derive(Clone, Debug)]
@@ -481,6 +483,7 @@ impl<'a> Parser<'a> {
             },
             current_closure: None,
             recovery: Recovery::Allowed,
+            is_in_const_env: false,
         };
 
         // Make parser point to the first token.
@@ -1320,7 +1323,7 @@ impl<'a> Parser<'a> {
             self.psess.gated_spans.gate(sym::inline_const_pat, span);
         }
         self.expect_keyword(kw::Const)?;
-        let (attrs, blk) = self.parse_inner_attrs_and_block()?;
+        let (attrs, blk) = self.with_const_management(|this| this.parse_inner_attrs_and_block())?;
         let anon_const = AnonConst {
             id: DUMMY_NODE_ID,
             value: self.mk_expr(blk.span, ExprKind::Block(blk, None)),
@@ -1650,6 +1653,13 @@ impl<'a> Parser<'a> {
     pub fn approx_token_stream_pos(&self) -> u32 {
         self.num_bump_calls
     }
+
+    fn with_const_management<T>(&mut self, f: impl FnOnce(&mut Self) -> T) -> T {
+        self.is_in_const_env = true;
+        let rslt = f(self);
+        self.is_in_const_env = false;
+        rslt
+    }
 }
 
 pub(crate) fn make_unclosed_delims_error(

compiler/rustc_parse/src/parser/pat.rs

@@ -1098,7 +1098,7 @@ impl<'a> Parser<'a> {
     fn parse_pat_mac_invoc(&mut self, path: Path) -> PResult<'a, PatKind> {
         self.bump();
         let args = self.parse_delim_args()?;
-        let mac = P(MacCall { path, args });
+        let mac = P(MacCall { is_in_const_env: self.is_in_const_env, path, args });
         Ok(PatKind::MacCall(mac))
     }
 

compiler/rustc_parse/src/parser/path.rs

@@ -843,11 +843,13 @@ impl<'a> Parser<'a> {
     /// the caller.
     pub(super) fn parse_const_arg(&mut self) -> PResult<'a, AnonConst> {
         // Parse const argument.
-        let value = if let token::OpenDelim(Delimiter::Brace) = self.token.kind {
-            self.parse_expr_block(None, self.token.span, BlockCheckMode::Default)?
-        } else {
-            self.handle_unambiguous_unbraced_const_arg()?
-        };
+        let value = self.with_const_management(|this| {
+            if let token::OpenDelim(Delimiter::Brace) = this.token.kind {
+                this.parse_expr_block(None, this.token.span, BlockCheckMode::Default)
+            } else {
+                this.handle_unambiguous_unbraced_const_arg()
+            }
+        })?;
         Ok(AnonConst { id: ast::DUMMY_NODE_ID, value })
     }
 

compiler/rustc_parse/src/parser/stmt.rs

@@ -226,7 +226,7 @@ impl<'a> Parser<'a> {
             _ => MacStmtStyle::NoBraces,
         };
 
-        let mac = P(MacCall { path, args });
+        let mac = P(MacCall { is_in_const_env: self.is_in_const_env, path, args });
 
         let kind = if (style == MacStmtStyle::Braces
             && self.token != token::Dot

compiler/rustc_parse/src/parser/ty.rs

@@ -758,7 +758,11 @@ impl<'a> Parser<'a> {
         let path = self.parse_path_inner(PathStyle::Type, ty_generics)?;
         if self.eat(&token::Not) {
             // Macro invocation in type position
-            Ok(TyKind::MacCall(P(MacCall { path, args: self.parse_delim_args()? })))
+            Ok(TyKind::MacCall(P(MacCall {
+                is_in_const_env: self.is_in_const_env,
+                path,
+                args: self.parse_delim_args()?,
+            })))
         } else if allow_plus == AllowPlus::Yes && self.check_plus() {
             // `Trait1 + Trait2 + 'a`
             self.parse_remaining_bounds_path(ThinVec::new(), path, lo, true)

tests/ui/macros/rfc-2011-nicer-assert-messages/const-environments.rs

@@ -0,0 +1,19 @@
+#![feature(core_intrinsics, generic_assert)]
+
+const _: () = {
+    let foo = 1;
+    assert!(foo == 3);
+    //~^ERROR: evaluation of constant value failed
+};
+
+fn main() {
+    const {
+        let foo = 1;
+        assert!(foo == 3);
+    }
+
+    const fn bar() {
+        let foo = 1;
+        assert!(foo == 3);
+    }
+}

tests/ui/macros/rfc-2011-nicer-assert-messages/const-environments.stderr

@@ -0,0 +1,11 @@
+error[E0080]: evaluation of constant value failed
+  --> $DIR/const-environments.rs:5:5
+   |
+LL |     assert!(foo == 3);
+   |     ^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'assertion failed: foo == 3', $DIR/const-environments.rs:5:5
+   |
+   = 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 E0080`.