fix issues and ui test

Author: fee1-dead

compiler/rustc_middle/src/ty/mod.rs

@@ -2181,7 +2181,8 @@ impl<'tcx> TyCtxt<'tcx> {
                         self.constness(def_id) == hir::Constness::Const
                     }
                     DefKind::Impl { of_trait: true } => {
-                        self.constness(self.trait_item_of(def_id).unwrap()) == hir::Constness::Const
+                        let Some(trait_method_did) = self.trait_item_of(def_id) else { return false; };
+                        self.constness(trait_method_did) == hir::Constness::Const
                             && self.is_conditionally_const(parent_def_id)
                     }
                     DefKind::Trait => {

tests/ui/typeck/typeck_type_placeholder_item.stderr

@@ -684,13 +684,6 @@ error[E0015]: cannot call non-const method `<std::ops::Range<i32> as Iterator>::
 LL | const _: _ = (1..10).filter(|x| x % 2 == 0).map(|x| x * x);
    |                      ^^^^^^^^^^^^^^^^^^^^^^
    |
-note: method `filter` is not const because trait `Iterator` is not const
-  --> $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
-   |
-   = note: this trait is not const
-  ::: $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
-   |
-   = note: this method is not const
    = note: calls in constants are limited to constant functions, tuple structs and tuple variants
 
 error[E0015]: cannot call non-const method `<Filter<std::ops::Range<i32>, {closure@$DIR/typeck_type_placeholder_item.rs:240:29: 240:32}> as Iterator>::map::<i32, {closure@$DIR/typeck_type_placeholder_item.rs:240:49: 240:52}>` in constants
@@ -699,13 +692,6 @@ error[E0015]: cannot call non-const method `<Filter<std::ops::Range<i32>, {closu
 LL | const _: _ = (1..10).filter(|x| x % 2 == 0).map(|x| x * x);
    |                                             ^^^^^^^^^^^^^^
    |
-note: method `map` is not const because trait `Iterator` is not const
-  --> $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
-   |
-   = note: this trait is not const
-  ::: $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
-   |
-   = note: this method is not const
    = note: calls in constants are limited to constant functions, tuple structs and tuple variants
 
 error: aborting due to 83 previous errors