Fix ICE when passing DefId-creating args to legacy_const_generics.

1 files changed, 67 insertions, 3 deletions

diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index b7cf2d252dc..3af29838b72 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -1,18 +1,22 @@
 use std::assert_matches::assert_matches;
+use std::ops::ControlFlow;
 
 use rustc_ast::ptr::P as AstP;
 use rustc_ast::*;
+use rustc_ast_pretty::pprust::expr_to_string;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_data_structures::sync::Lrc;
 use rustc_hir as hir;
 use rustc_hir::HirId;
 use rustc_hir::def::{DefKind, Res};
 use rustc_middle::span_bug;
+use rustc_middle::ty::TyCtxt;
 use rustc_session::errors::report_lit_error;
 use rustc_span::source_map::{Spanned, respan};
 use rustc_span::symbol::{Ident, Symbol, kw, sym};
 use rustc_span::{DUMMY_SP, DesugaringKind, Span};
 use thin_vec::{ThinVec, thin_vec};
+use visit::{Visitor, walk_expr};
 
 use super::errors::{
     AsyncCoroutinesNotSupported, AwaitOnlyInAsyncFnAndBlocks, BaseExpressionDoubleDot,
@@ -23,9 +27,32 @@ use super::errors::{
 use super::{
     GenericArgsMode, ImplTraitContext, LoweringContext, ParamMode, ResolverAstLoweringExt,
 };
-use crate::errors::YieldInClosure;
+use crate::errors::{InvalidLegacyConstGenericArg, UseConstGenericArg, YieldInClosure};
 use crate::{AllowReturnTypeNotation, FnDeclKind, ImplTraitPosition, fluent_generated};
 
+struct WillCreateDefIdsVisitor {}
+
+impl<'v> rustc_ast::visit::Visitor<'v> for WillCreateDefIdsVisitor {
+    type Result = ControlFlow<Span>;
+
+    fn visit_anon_const(&mut self, c: &'v AnonConst) -> Self::Result {
+        ControlFlow::Break(c.value.span)
+    }
+
+    fn visit_item(&mut self, item: &'v Item) -> Self::Result {
+        ControlFlow::Break(item.span)
+    }
+
+    fn visit_expr(&mut self, ex: &'v Expr) -> Self::Result {
+        match ex.kind {
+            ExprKind::Gen(..) | ExprKind::ConstBlock(..) | ExprKind::Closure(..) => {
+                ControlFlow::Break(ex.span)
+            }
+            _ => walk_expr(self, ex),
+        }
+    }
+}
+
 impl<'hir> LoweringContext<'_, 'hir> {
     fn lower_exprs(&mut self, exprs: &[AstP<Expr>]) -> &'hir [hir::Expr<'hir>] {
         self.arena.alloc_from_iter(exprs.iter().map(|x| self.lower_expr_mut(x)))
@@ -396,10 +423,34 @@ impl<'hir> LoweringContext<'_, 'hir> {
             unreachable!();
         };
 
+        let mut error = None;
+        let mut invalid_expr_error = |tcx: TyCtxt<'_>, span| {
+            // Avoid emitting the error multiple times.
+            if error.is_none() {
+                let mut const_args = vec![];
+                let mut other_args = vec![];
+                for (idx, arg) in args.iter().enumerate() {
+                    if legacy_args_idx.contains(&idx) {
+                        const_args.push(format!("{{ {} }}", expr_to_string(arg)));
+                    } else {
+                        other_args.push(expr_to_string(arg));
+                    }
+                }
+                let suggestion = UseConstGenericArg {
+                    end_of_fn: f.span.shrink_to_hi(),
+                    const_args: const_args.join(", "),
+                    other_args: other_args.join(", "),
+                    call_args: args[0].span.to(args.last().unwrap().span),
+                };
+                error = Some(tcx.dcx().emit_err(InvalidLegacyConstGenericArg { span, suggestion }));
+            }
+            error.unwrap()
+        };
+
         // Split the arguments into const generics and normal arguments
         let mut real_args = vec![];
         let mut generic_args = ThinVec::new();
-        for (idx, arg) in args.into_iter().enumerate() {
+        for (idx, arg) in args.iter().cloned().enumerate() {
             if legacy_args_idx.contains(&idx) {
                 let parent_def_id = self.current_def_id_parent;
                 let node_id = self.next_node_id();
@@ -410,7 +461,20 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     self.create_def(parent_def_id, node_id, kw::Empty, DefKind::AnonConst, f.span);
                 }
 
-                let anon_const = AnonConst { id: node_id, value: arg };
+                let mut visitor = WillCreateDefIdsVisitor {};
+                let const_value = if let ControlFlow::Break(span) = visitor.visit_expr(&arg) {
+                    AstP(Expr {
+                        id: self.next_node_id(),
+                        kind: ExprKind::Err(invalid_expr_error(self.tcx, span)),
+                        span: f.span,
+                        attrs: [].into(),
+                        tokens: None,
+                    })
+                } else {
+                    arg
+                };
+
+                let anon_const = AnonConst { id: node_id, value: const_value };
                 generic_args.push(AngleBracketedArg::Arg(GenericArg::Const(anon_const)));
             } else {
                 real_args.push(arg);