Remove handling of ConstBlock in pattern lowering to prevent ICE

Author: Shinonn23

compiler/rustc_ast_lowering/src/pat.rs

@@ -399,7 +399,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             ExprKind::Lit(lit) => {
                 hir::PatExprKind::Lit { lit: self.lower_lit(lit, span), negated: false }
             }
-            ExprKind::ConstBlock(c) => hir::PatExprKind::ConstBlock(self.lower_const_block(c)),
             ExprKind::IncludedBytes(byte_sym) => hir::PatExprKind::Lit {
                 lit: respan(span, LitKind::ByteStr(*byte_sym, StrStyle::Cooked)),
                 negated: false,

tests/ui/pattern/deref-patterns/ice-adjust-mode-unimplemented-for-constblock.rs

@@ -0,0 +1,17 @@
+// Regression test for #148138
+// Ensure that const blocks in patterns are rejected with a proper error
+// instead of causing an ICE in the type checker.
+//
+// The vec! macro expansion bypasses parser validation for const blocks in patterns,
+// so this must be caught during AST lowering.
+
+#![feature(deref_patterns)]
+#![expect(incomplete_features)]
+
+fn main() {
+    let vec![const { vec![] }]: Vec<usize> = vec![];
+    //~^ ERROR expected a pattern, found a function call
+    //~| ERROR usage of qualified paths in this context is experimental
+    //~| ERROR expected tuple struct or tuple variant
+    //~| ERROR arbitrary expressions aren't allowed in patterns
+}

tests/ui/pattern/deref-patterns/ice-adjust-mode-unimplemented-for-constblock.stderr

@@ -0,0 +1,39 @@
+error[E0532]: expected a pattern, found a function call
+  --> $DIR/ice-adjust-mode-unimplemented-for-constblock.rs:12:9
+   |
+LL |     let vec![const { vec![] }]: Vec<usize> = vec![];
+   |         ^^^^^^^^^^^^^^^^^^^^^^ not a tuple struct or tuple variant
+   |
+   = note: function calls are not allowed in patterns: <https://doc.rust-lang.org/book/ch19-00-patterns.html>
+   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0658]: usage of qualified paths in this context is experimental
+  --> $DIR/ice-adjust-mode-unimplemented-for-constblock.rs:12:9
+   |
+LL |     let vec![const { vec![] }]: Vec<usize> = vec![];
+   |         ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #86935 <https://github.com/rust-lang/rust/issues/86935> for more information
+   = help: add `#![feature(more_qualified_paths)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: arbitrary expressions aren't allowed in patterns
+  --> $DIR/ice-adjust-mode-unimplemented-for-constblock.rs:12:14
+   |
+LL |     let vec![const { vec![] }]: Vec<usize> = vec![];
+   |              ^^^^^^^^^^^^^^^^
+
+error[E0164]: expected tuple struct or tuple variant, found associated function `<[_]>::into_vec`
+  --> $DIR/ice-adjust-mode-unimplemented-for-constblock.rs:12:9
+   |
+LL |     let vec![const { vec![] }]: Vec<usize> = vec![];
+   |         ^^^^^^^^^^^^^^^^^^^^^^ `fn` calls are not allowed in patterns
+   |
+   = help: for more information, visit https://doc.rust-lang.org/book/ch19-00-patterns.html
+   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0164, E0532, E0658.
+For more information about an error, try `rustc --explain E0164`.