Rollup merge of #105147 - nbdd0121:inline_const_unsafe, r=oli-obk

Allow unsafe through inline const

Handle similar to closures.

Address https://github.com/rust-lang/rust/pull/104087#issuecomment-1324173328

Note that this PR does not fix the issue for `unsafe { [0; function_requiring_unsafe()] }`. This is fundamentally unfixable for MIR unsafeck IMO.

This PR also does not fix unsafety checking for inline const in pattern position. It actually breaks it, allowing unsafe functions to be used in inline const in pattern position without unsafe blocks. Inline const in pattern position is not visible in MIR so ignored by MIR unsafety checking (currently it is also not checked by borrow checker, which is the reason why it's considered an incomplete feature).

`@rustbot` label: +T-lang +F-inline_const

src/test/ui/inline-const/expr-unsafe-err.mir.stderr

@@ -0,0 +1,11 @@
+error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
+  --> $DIR/expr-unsafe-err.rs:8:9
+   |
+LL |         require_unsafe();
+   |         ^^^^^^^^^^^^^^^^ call to unsafe function
+   |
+   = note: consult the function's documentation for information on how to avoid undefined behavior
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0133`.

src/test/ui/inline-const/expr-unsafe-err.rs

@@ -0,0 +1,11 @@
+// revisions: mir thir
+// [thir]compile-flags: -Z thir-unsafeck
+#![feature(inline_const)]
+const unsafe fn require_unsafe() -> usize { 1 }
+
+fn main() {
+    const {
+        require_unsafe();
+        //~^ ERROR [E0133]
+    }
+}

src/test/ui/inline-const/expr-unsafe-err.thir.stderr

@@ -0,0 +1,11 @@
+error[E0133]: call to unsafe function `require_unsafe` is unsafe and requires unsafe function or block
+  --> $DIR/expr-unsafe-err.rs:8:9
+   |
+LL |         require_unsafe();
+   |         ^^^^^^^^^^^^^^^^ call to unsafe function
+   |
+   = note: consult the function's documentation for information on how to avoid undefined behavior
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0133`.

src/test/ui/inline-const/expr-unsafe.mir.stderr

@@ -0,0 +1,14 @@
+warning: unnecessary `unsafe` block
+  --> $DIR/expr-unsafe.rs:12:13
+   |
+LL |             unsafe {}
+   |             ^^^^^^ unnecessary `unsafe` block
+   |
+note: the lint level is defined here
+  --> $DIR/expr-unsafe.rs:4:9
+   |
+LL | #![warn(unused_unsafe)]
+   |         ^^^^^^^^^^^^^
+
+warning: 1 warning emitted
+

src/test/ui/inline-const/expr-unsafe.rs

@@ -0,0 +1,16 @@
+// check-pass
+// revisions: mir thir
+// [thir]compile-flags: -Z thir-unsafeck
+#![warn(unused_unsafe)]
+#![feature(inline_const)]
+const unsafe fn require_unsafe() -> usize { 1 }
+
+fn main() {
+    unsafe {
+        const {
+            require_unsafe();
+            unsafe {}
+            //~^ WARNING unnecessary `unsafe` block
+        }
+    }
+}

src/test/ui/inline-const/expr-unsafe.thir.stderr

@@ -0,0 +1,17 @@
+warning: unnecessary `unsafe` block
+  --> $DIR/expr-unsafe.rs:12:13
+   |
+LL |     unsafe {
+   |     ------ because it's nested under this `unsafe` block
+...
+LL |             unsafe {}
+   |             ^^^^^^ unnecessary `unsafe` block
+   |
+note: the lint level is defined here
+  --> $DIR/expr-unsafe.rs:4:9
+   |
+LL | #![warn(unused_unsafe)]
+   |         ^^^^^^^^^^^^^
+
+warning: 1 warning emitted
+

src/test/ui/inline-const/pat-unsafe-err.rs

@@ -0,0 +1,17 @@
+// ignore-test This is currently broken
+// revisions: mir thir
+// [thir]compile-flags: -Z thir-unsafeck
+
+#![allow(incomplete_features)]
+#![feature(inline_const_pat)]
+
+const unsafe fn require_unsafe() -> usize { 1 }
+
+fn main() {
+    match () {
+        const {
+            require_unsafe();
+            //~^ ERROR [E0133]
+        } => (),
+    }
+}

src/test/ui/inline-const/pat-unsafe.rs

@@ -0,0 +1,22 @@
+// ignore-test This is currently broken
+// check-pass
+// revisions: mir thir
+// [thir]compile-flags: -Z thir-unsafeck
+
+#![allow(incomplete_features)]
+#![warn(unused_unsafe)]
+#![feature(inline_const_pat)]
+
+const unsafe fn require_unsafe() -> usize { 1 }
+
+fn main() {
+    unsafe {
+        match () {
+            const {
+                require_unsafe();
+                unsafe {}
+                //~^ WARNING unnecessary `unsafe` block
+            } => (),
+        }
+    }
+}