Rollup merge of #116284 - RalfJung:no-nan-match, r=cjgillot

make matching on NaN a hard error, and remove the rest of illegal_floating_point_literal_pattern

These arms would never be hit anyway, so the pattern makes little sense. We have had a future-compat lint against float matches in general for a *long* time, so I hope we can get away with immediately making this a hard error.

This is part of implementing rust-lang/rfcs#3535.

Closes #41620 by removing the lint.

rust-lang/reference#1456 updates the reference to match.

Author: matthiaskrgr

tests/ui/expect_tool_lint_rfc_2383.rs

@@ -20,12 +20,8 @@ mod rustc_ok {
     pub fn rustc_lints() {
         let x = 42.0;
 
-        #[expect(illegal_floating_point_literal_pattern)]
-        match x {
-            5.0 => {}
-            6.0 => {}
-            _ => {}
-        }
+        #[expect(invalid_nan_comparisons)]
+        let _b = x == f32::NAN;
     }
 }
 
@@ -38,13 +34,9 @@ mod rustc_warn {
     pub fn rustc_lints() {
         let x = 42;
 
-        #[expect(illegal_floating_point_literal_pattern)]
+        #[expect(invalid_nan_comparisons)]
         //~^ ERROR: this lint expectation is unfulfilled
-        match x {
-            5 => {}
-            6 => {}
-            _ => {}
-        }
+        let _b = x == 5;
     }
 }
 

tests/ui/expect_tool_lint_rfc_2383.stderr

@@ -1,5 +1,5 @@
 error: this lint expectation is unfulfilled
-  --> $DIR/expect_tool_lint_rfc_2383.rs:35:14
+  --> $DIR/expect_tool_lint_rfc_2383.rs:31:14
    |
 LL |     #[expect(dead_code)]
    |              ^^^^^^^^^
@@ -8,31 +8,31 @@ LL |     #[expect(dead_code)]
    = help: to override `-D warnings` add `#[allow(unfulfilled_lint_expectations)]`
 
 error: this lint expectation is unfulfilled
-  --> $DIR/expect_tool_lint_rfc_2383.rs:41:18
+  --> $DIR/expect_tool_lint_rfc_2383.rs:37:18
    |
-LL |         #[expect(illegal_floating_point_literal_pattern)]
-   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |         #[expect(invalid_nan_comparisons)]
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this lint expectation is unfulfilled
-  --> $DIR/expect_tool_lint_rfc_2383.rs:116:14
+  --> $DIR/expect_tool_lint_rfc_2383.rs:108:14
    |
 LL |     #[expect(clippy::almost_swapped)]
    |              ^^^^^^^^^^^^^^^^^^^^^^
 
 error: this lint expectation is unfulfilled
-  --> $DIR/expect_tool_lint_rfc_2383.rs:124:14
+  --> $DIR/expect_tool_lint_rfc_2383.rs:116:14
    |
 LL |     #[expect(clippy::bytes_nth)]
    |              ^^^^^^^^^^^^^^^^^
 
 error: this lint expectation is unfulfilled
-  --> $DIR/expect_tool_lint_rfc_2383.rs:130:14
+  --> $DIR/expect_tool_lint_rfc_2383.rs:122:14
    |
 LL |     #[expect(clippy::if_same_then_else)]
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this lint expectation is unfulfilled
-  --> $DIR/expect_tool_lint_rfc_2383.rs:136:14
+  --> $DIR/expect_tool_lint_rfc_2383.rs:128:14
    |
 LL |     #[expect(clippy::overly_complex_bool_expr)]
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^