Emit fatal on invalid const args with nested defs

Author: mu001999

compiler/rustc_ast_lowering/src/expr.rs

@@ -29,7 +29,7 @@ use super::{
 use crate::errors::{InvalidLegacyConstGenericArg, UseConstGenericArg, YieldInClosure};
 use crate::{AllowReturnTypeNotation, FnDeclKind, ImplTraitPosition, TryBlockScope};
 
-struct WillCreateDefIdsVisitor {}
+pub(super) struct WillCreateDefIdsVisitor;
 
 impl<'v> rustc_ast::visit::Visitor<'v> for WillCreateDefIdsVisitor {
     type Result = ControlFlow<Span>;
@@ -479,18 +479,18 @@ impl<'hir, R: ResolverAstLoweringExt<'hir>> LoweringContext<'_, 'hir, R> {
                     DefPathData::LateAnonConst,
                     f.span,
                 );
-                let mut visitor = WillCreateDefIdsVisitor {};
-                let const_value = if let ControlFlow::Break(span) = visitor.visit_expr(&arg) {
-                    Box::new(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 const_value =
+                    if let ControlFlow::Break(span) = WillCreateDefIdsVisitor.visit_expr(&arg) {
+                        Box::new(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,

compiler/rustc_ast_lowering/src/lib.rs

@@ -39,7 +39,7 @@ use std::mem;
 use std::sync::Arc;
 
 use rustc_ast::node_id::NodeMap;
-use rustc_ast::visit::AssocCtxt;
+use rustc_ast::visit::{AssocCtxt, Visitor};
 use rustc_ast::{self as ast, *};
 use rustc_attr_parsing::{AttributeParser, Late, OmitDoc};
 use rustc_data_structures::fingerprint::Fingerprint;
@@ -2580,12 +2580,14 @@ impl<'hir, R: ResolverAstLoweringExt<'hir>> LoweringContext<'_, 'hir, R> {
         let span = self.lower_span(expr.span);
 
         let overly_complex_const = |this: &mut Self| {
-            let e = this.dcx().struct_span_err(
-                expr.span,
-                "complex const arguments must be placed inside of a `const` block",
-            );
+            let msg = "complex const arguments must be placed inside of a `const` block";
+            let e = if expr::WillCreateDefIdsVisitor.visit_expr(expr).is_break() {
+                this.dcx().struct_span_fatal(expr.span, msg).emit()
+            } else {
+                this.dcx().struct_span_err(expr.span, msg).emit()
+            };
 
-            ConstArg { hir_id: this.next_id(), kind: hir::ConstArgKind::Error(e.emit()), span }
+            ConstArg { hir_id: this.next_id(), kind: hir::ConstArgKind::Error(e), span }
         };
 
         match &expr.kind {

tests/ui/const-generics/mgca/array-expr-complex.r1.stderr

@@ -0,0 +1,8 @@
+error: complex const arguments must be placed inside of a `const` block
+  --> $DIR/array-expr-complex.rs:11:28
+   |
+LL |     takes_array::<{ [1, 2, 1 + 2] }>();
+   |                            ^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/const-generics/mgca/array-expr-complex.r2.stderr

@@ -0,0 +1,8 @@
+error: complex const arguments must be placed inside of a `const` block
+  --> $DIR/array-expr-complex.rs:14:21
+   |
+LL |     takes_array::<{ [X; 3] }>();
+   |                     ^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/const-generics/mgca/array-expr-complex.r3.stderr

@@ -0,0 +1,8 @@
+error: complex const arguments must be placed inside of a `const` block
+  --> $DIR/array-expr-complex.rs:17:21
+   |
+LL |     takes_array::<{ [0; Y] }>();
+   |                     ^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/const-generics/mgca/array-expr-complex.rs

@@ -1,16 +1,21 @@
+//@ revisions: r1 r2 r3
+
 #![expect(incomplete_features)]
 #![feature(min_generic_const_args, adt_const_params)]
 
 fn takes_array<const A: [u32; 3]>() {}
 
 fn generic_caller<const X: u32, const Y: usize>() {
     // not supported yet
+    #[cfg(r1)]
     takes_array::<{ [1, 2, 1 + 2] }>();
-    //~^ ERROR: complex const arguments must be placed inside of a `const` block
+    //[r1]~^ ERROR: complex const arguments must be placed inside of a `const` block
+    #[cfg(r2)]
     takes_array::<{ [X; 3] }>();
-    //~^ ERROR: complex const arguments must be placed inside of a `const` block
+    //[r2]~^ ERROR: complex const arguments must be placed inside of a `const` block
+    #[cfg(r3)]
     takes_array::<{ [0; Y] }>();
-    //~^ ERROR: complex const arguments must be placed inside of a `const` block
+    //[r3]~^ ERROR: complex const arguments must be placed inside of a `const` block
 }
 
 fn main() {}

tests/ui/const-generics/mgca/array-expr-complex.stderr

@@ -0,0 +1,12 @@
+#![feature(min_generic_const_args)]
+
+trait Iter<
+    const FN: fn() = {
+        || { //~ ERROR complex const arguments must be placed inside of a `const` block
+            use std::io::*;
+            write!(_, "")
+        }
+    },
+>
+{
+}

tests/ui/const-generics/mgca/bad-const-arg-fn-154539.rs

@@ -0,0 +1,11 @@
+error: complex const arguments must be placed inside of a `const` block
+  --> $DIR/bad-const-arg-fn-154539.rs:5:9
+   |
+LL | /         || {
+LL | |             use std::io::*;
+LL | |             write!(_, "")
+LL | |         }
+   | |_________^
+
+error: aborting due to 1 previous error
+