Auto merge of #110107 - cjgillot:const-prop-lint-junk, r=oli-obk

Ensure mir_drops_elaborated_and_const_checked when requiring codegen.

mir_drops_elaborated_and_const_checked may emit errors while codegen has started, and the compiler would exit leaving object code files around.

Found by `@cuviper` in #109731

Author: bors

compiler/rustc_interface/src/passes.rs

@@ -794,8 +794,14 @@ fn analysis(tcx: TyCtxt<'_>, (): ()) -> Result<()> {
             }
             tcx.ensure().has_ffi_unwind_calls(def_id);
 
-            if tcx.hir().body_const_context(def_id).is_some() {
+            // If we need to codegen, ensure that we emit all errors from
+            // `mir_drops_elaborated_and_const_checked` now, to avoid discovering
+            // them later during codegen.
+            if tcx.sess.opts.output_types.should_codegen()
+                || tcx.hir().body_const_context(def_id).is_some()
+            {
                 tcx.ensure().mir_drops_elaborated_and_const_checked(def_id);
+                tcx.ensure().unused_generic_params(ty::InstanceDef::Item(def_id.to_def_id()));
             }
         }
     });

src/tools/miri/tests/fail/const-ub-checks.stderr

@@ -4,6 +4,12 @@ error[E0080]: evaluation of constant value failed
 LL |     ptr.read();
    |     ^^^^^^^^^^ accessing memory with alignment ALIGN, but alignment ALIGN is required
 
+note: erroneous constant used
+  --> $DIR/const-ub-checks.rs:LL:CC
+   |
+LL |     let _x = UNALIGNED_READ;
+   |              ^^^^^^^^^^^^^^
+
 error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0080`.

src/tools/miri/tests/fail/erroneous_const2.stderr

@@ -4,6 +4,20 @@ error[E0080]: evaluation of constant value failed
 LL | const FOO: u32 = [X - Y, Y - X][(X < Y) as usize];
    |                   ^^^^^ attempt to compute `5_u32 - 6_u32`, which would overflow
 
+note: erroneous constant used
+  --> $DIR/erroneous_const2.rs:LL:CC
+   |
+LL |     println!("{}", FOO);
+   |                    ^^^
+
+note: erroneous constant used
+  --> $DIR/erroneous_const2.rs:LL:CC
+   |
+LL |     println!("{}", FOO);
+   |                    ^^^
+   |
+   = note: this note originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
+
 error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0080`.

src/tools/miri/tests/pass/track-alloc-1.rs

@@ -0,0 +1,9 @@
+include ../tools.mk
+
+# Test that emitting an error because of arithmetic
+# overflow lint does not leave .o files around
+# because of interrupted codegen.
+
+all:
+	$(RUSTC) input.rs; test $$? -eq 1
+	ls *.o; test $$? -ne 0

src/tools/miri/tests/pass/track-alloc-1.stderr

@@ -0,0 +1,5 @@
+#![deny(arithmetic_overflow)]
+
+fn main() {
+    let x = 255u8 + 1;
+}

tests/run-make/const-prop-lint/Makefile

@@ -1,6 +1,8 @@
 // This checks that the const-eval ICE in issue #100878 does not recur.
 //
 // build-pass
+
+#[allow(arithmetic_overflow)]
 pub fn bitshift_data(data: [u8; 1]) -> u8 {
     data[0] << 8
 }

tests/run-make/const-prop-lint/input.rs

@@ -1,6 +1,7 @@
 // build-pass
 #![allow(dead_code)]
 #![allow(unused_variables)]
+#![allow(unconditional_panic)]
 const A: [u32; 1] = [0];
 
 fn test() {

tests/ui/consts/const-eval/issue-100878.rs

@@ -15,12 +15,6 @@ LL | pub fn unused_type<T>() -> impl Generator<(), Yield = u32, Return = u32> +
 LL |     || {
    |     ^^
 
-note: the above error was encountered while instantiating `fn finish::<[generator@$DIR/generators.rs:35:5: 35:7], u32, u32>`
-  --> $DIR/generators.rs:86:5
-   |
-LL |     finish(unused_type::<u32>());
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
 error: item has unused generic parameters
   --> $DIR/generators.rs:60:5
    |
@@ -29,11 +23,5 @@ LL | pub fn unused_const<const T: u32>() -> impl Generator<(), Yield = u32, Retu
 LL |     || {
    |     ^^
 
-note: the above error was encountered while instantiating `fn finish::<[generator@$DIR/generators.rs:60:5: 60:7], u32, u32>`
-  --> $DIR/generators.rs:89:5
-   |
-LL |     finish(unused_const::<1u32>());
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
 error: aborting due to 2 previous errors; 1 warning emitted