Auto merge of rust-lang#134126 - c410-f3r:hocus-pocus, r=<try>

[`generic_assert`] Avoid constant environments

cc rust-lang#44838

This PR is a work in progress. Requesting an early perf run to evaluate possible impacts.

The `generic_assert` feature captures variables for printing purposes.

```rust
fn foo() {
  let elem = 1i32;
  assert!(&elem);
}

// Expansion
fn foo() {
  let elem = 1i32;
  {
    use ::core::asserting::{TryCaptureGeneric, TryCapturePrintable};
    let mut __capture0 = ::core::asserting::Capture::new();
    let __local_bind0 = &elem;
    if (!&*__local_bind0) {
        (&::core::asserting::Wrapper(__local_bind0)).try_capture(&mut __capture0);
        {
          ::std::rt::panic_fmt(format_args!("Assertion failed: &elem\nWith captures:\n  elem = {0:?}\n", __capture0));
        }
      }
  };
}
```

The problem is that such a thing is complicated in constant environments. At the current time only strings are allowed and a full support parity with non-constant environments is, as far as I can tell, not feasible in the foreseen future.

```rust
fn foo() {
  // !!! ERROR !!!
  const {
    let elem = 1i32;
    assert!(&elem);
  }
}
```

Therefore, `generic_assert` will not be triggered in constant environment through an `is_in_const_env` variable flag originated in the `rustc_parse` crate.

Author: bors

compiler/rustc_ast/src/ast.rs

@@ -1718,6 +1718,7 @@ 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

@@ -711,7 +711,7 @@ 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

@@ -1008,7 +1008,7 @@ 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,