Auto merge of #109303 - matthiaskrgr:rollup-usj4ef5, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #107416 (Error code E0794 for late-bound lifetime parameter error.)
 - #108772 (Speed up tidy quite a lot)
 - #109193 (Add revisions for -Zlower-impl-trait-in-trait-to-assoc-ty fixed tests)
 - #109234 (Tweak implementation of overflow checking assertions)
 - #109238 (Fix generics mismatch errors for RPITITs on -Zlower-impl-trait-in-trait-to-assoc-ty)
 - #109283 (rustdoc: reduce allocations in `visibility_to_src_with_space`)
 - #109287 (Use `size_of_val` instead of manual calculation)
 - #109288 (Stabilise `unix_socket_abstract`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

.gitignore

@@ -42,6 +42,7 @@ no_llvm_build
 /llvm/
 /mingw-build/
 build/
+!/compiler/rustc_mir_build/src/build/
 /build-rust-analyzer/
 /dist/
 /unicode-downloads

compiler/rustc_codegen_cranelift/src/base.rs

@@ -346,17 +346,10 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
                 crate::abi::codegen_return(fx);
             }
             TerminatorKind::Assert { cond, expected, msg, target, cleanup: _ } => {
-                if !fx.tcx.sess.overflow_checks() {
-                    let overflow_not_to_check = match msg {
-                        AssertKind::OverflowNeg(..) => true,
-                        AssertKind::Overflow(op, ..) => op.is_checkable(),
-                        _ => false,
-                    };
-                    if overflow_not_to_check {
-                        let target = fx.get_block(*target);
-                        fx.bcx.ins().jump(target, &[]);
-                        continue;
-                    }
+                if !fx.tcx.sess.overflow_checks() && msg.is_optional_overflow_check() {
+                    let target = fx.get_block(*target);
+                    fx.bcx.ins().jump(target, &[]);
+                    continue;
                 }
                 let cond = codegen_operand(fx, cond).load_scalar(fx);
 

compiler/rustc_codegen_ssa/src/glue.rs

@@ -46,7 +46,7 @@ pub fn size_and_align_of_dst<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
                 // NOTE: ideally, we want the effects of both `unchecked_smul` and `unchecked_umul`
                 // (resulting in `mul nsw nuw` in LLVM IR), since we know that the multiplication
                 // cannot signed wrap, and that both operands are non-negative. But at the time of writing,
-                // `BuilderMethods` can't do this, and it doesn't seem to enable any further optimizations.
+                // the `LLVM-C` binding can't do this, and it doesn't seem to enable any further optimizations.
                 bx.unchecked_smul(info.unwrap(), bx.const_usize(unit.size.bytes())),
                 bx.const_usize(unit.align.abi.bytes()),
             )

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -563,15 +563,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         // with #[rustc_inherit_overflow_checks] and inlined from
         // another crate (mostly core::num generic/#[inline] fns),
         // while the current crate doesn't use overflow checks.
-        if !bx.cx().check_overflow() {
-            let overflow_not_to_check = match msg {
-                AssertKind::OverflowNeg(..) => true,
-                AssertKind::Overflow(op, ..) => op.is_checkable(),
-                _ => false,
-            };
-            if overflow_not_to_check {
-                const_cond = Some(expected);
-            }
+        if !bx.cx().check_overflow() && msg.is_optional_overflow_check() {
+            const_cond = Some(expected);
         }
 
         // Don't codegen the panic block if success if known.

compiler/rustc_const_eval/src/interpret/machine.rs

@@ -155,7 +155,7 @@ pub trait Machine<'mir, 'tcx>: Sized {
 
     /// Whether Assert(OverflowNeg) and Assert(Overflow) MIR terminators should actually
     /// check for overflow.
-    fn ignore_checkable_overflow_assertions(_ecx: &InterpCx<'mir, 'tcx, Self>) -> bool;
+    fn ignore_optional_overflow_checks(_ecx: &InterpCx<'mir, 'tcx, Self>) -> bool;
 
     /// Entry point for obtaining the MIR of anything that should get evaluated.
     /// So not just functions and shims, but also const/static initializers, anonymous
@@ -474,7 +474,7 @@ pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
     }
 
     #[inline(always)]
-    fn ignore_checkable_overflow_assertions(_ecx: &InterpCx<$mir, $tcx, Self>) -> bool {
+    fn ignore_optional_overflow_checks(_ecx: &InterpCx<$mir, $tcx, Self>) -> bool {
         false
     }
 

compiler/rustc_const_eval/src/interpret/terminator.rs

@@ -138,12 +138,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             }
 
             Assert { ref cond, expected, ref msg, target, cleanup } => {
-                let ignored = M::ignore_checkable_overflow_assertions(self)
-                    && match msg {
-                        mir::AssertKind::OverflowNeg(..) => true,
-                        mir::AssertKind::Overflow(op, ..) => op.is_checkable(),
-                        _ => false,
-                    };
+                let ignored =
+                    M::ignore_optional_overflow_checks(self) && msg.is_optional_overflow_check();
                 let cond_val = self.read_scalar(&self.eval_operand(cond, None)?)?.to_bool()?;
                 if ignored || expected == cond_val {
                     self.go_to_block(target);

compiler/rustc_error_codes/src/error_codes.rs

@@ -513,6 +513,7 @@ E0790: include_str!("./error_codes/E0790.md"),
 E0791: include_str!("./error_codes/E0791.md"),
 E0792: include_str!("./error_codes/E0792.md"),
 E0793: include_str!("./error_codes/E0793.md"),
+E0794: include_str!("./error_codes/E0794.md"),
 }
 
 // Undocumented removed error codes. Note that many removed error codes are documented.

compiler/rustc_error_codes/src/error_codes/E0794.md

@@ -0,0 +1,64 @@
+A lifetime parameter of a function definition is called *late-bound* if it both:
+
+1. appears in an argument type
+2. does not appear in a generic type constraint
+
+You cannot specify lifetime arguments for late-bound lifetime parameters.
+
+Erroneous code example:
+
+```compile_fail,E0794
+fn foo<'a>(x: &'a str) -> &'a str { x }
+let _ = foo::<'static>;
+```
+
+The type of a concrete instance of a generic function is universally quantified
+over late-bound lifetime parameters. This is because we want the function to
+work for any lifetime substituted for the late-bound lifetime parameter, no
+matter where the function is called. Consequently, it doesn't make sense to
+specify arguments for late-bound lifetime parameters, since they are not
+resolved until the function's call site(s).
+
+To fix the issue, remove the specified lifetime:
+
+```
+fn foo<'a>(x: &'a str) -> &'a str { x }
+let _ = foo;
+```
+
+### Additional information
+
+Lifetime parameters that are not late-bound are called *early-bound*.
+Confusion may arise from the fact that late-bound and early-bound
+lifetime parameters are declared the same way in function definitions.
+When referring to a function pointer type, universal quantification over
+late-bound lifetime parameters can be made explicit:
+
+```
+trait BarTrait<'a> {}
+
+struct Bar<'a> {
+    s: &'a str
+}
+
+impl<'a> BarTrait<'a> for Bar<'a> {}
+
+fn bar<'a, 'b, T>(x: &'a str, _t: T) -> &'a str
+where T: BarTrait<'b>
+{
+    x
+}
+
+let bar_fn: for<'a> fn(&'a str, Bar<'static>) -> &'a str = bar; // OK
+let bar_fn2 = bar::<'static, Bar>; // Not allowed
+let bar_fn3 = bar::<Bar>; // OK
+```
+
+In the definition of `bar`, the lifetime parameter `'a` is late-bound, while
+`'b` is early-bound. This is reflected in the type annotation for `bar_fn`,
+where `'a` is universally quantified and `'b` is substituted by a specific
+lifetime. It is not allowed to explicitly specify early-bound lifetime
+arguments when late-bound lifetime parameters are present (as for `bar_fn2`,
+see issue #42868: https://github.com/rust-lang/rust/issues/42868), although the
+types that are constrained by early-bound parameters can be specified (as for
+`bar_fn3`).

compiler/rustc_hir_analysis/src/astconv/generics.rs

@@ -612,7 +612,7 @@ pub(crate) fn prohibit_explicit_late_bound_lifetimes(
         if position == GenericArgPosition::Value
             && args.num_lifetime_params() != param_counts.lifetimes
         {
-            let mut err = tcx.sess.struct_span_err(span, msg);
+            let mut err = struct_span_err!(tcx.sess, span, E0794, "{}", msg);
             err.span_note(span_late, note);
             err.emit();
         } else {

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -1205,6 +1205,17 @@ fn compare_number_of_generics<'tcx>(
         return Ok(());
     }
 
+    // We never need to emit a separate error for RPITITs, since if an RPITIT
+    // has mismatched type or const generic arguments, then the method that it's
+    // inheriting the generics from will also have mismatched arguments, and
+    // we'll report an error for that instead. Delay a bug for safety, though.
+    if tcx.opt_rpitit_info(trait_.def_id).is_some() {
+        return Err(tcx.sess.delay_span_bug(
+            rustc_span::DUMMY_SP,
+            "errors comparing numbers of generics of trait/impl functions were not emitted",
+        ));
+    }
+
     let matchings = [
         ("type", trait_own_counts.types, impl_own_counts.types),
         ("const", trait_own_counts.consts, impl_own_counts.consts),