Rollup merge of #70006 - petrochenkov:fresh, r=Centril

resolve: Fix two issues in fresh binding disambiguation

Prevent fresh bindings from shadowing ambiguity items.
Fixes https://github.com/rust-lang/rust/issues/46079

Correctly treat const generic parameters in fresh binding disambiguation.
Fixes https://github.com/rust-lang/rust/issues/68853

src/test/ui/binding/ambiguity-item.rs

@@ -0,0 +1,18 @@
+// Identifier pattern referring to an ambiguity item is an error (issue #46079).
+
+mod m {
+    pub fn f() {}
+}
+use m::*;
+
+mod n {
+    pub fn f() {}
+}
+use n::*; // OK, no conflict with `use m::*;`
+
+fn main() {
+    let v = f; //~ ERROR `f` is ambiguous
+    match v {
+        f => {} //~ ERROR `f` is ambiguous
+    }
+}

src/test/ui/binding/ambiguity-item.stderr

@@ -0,0 +1,41 @@
+error[E0659]: `f` is ambiguous (glob import vs glob import in the same module)
+  --> $DIR/ambiguity-item.rs:14:13
+   |
+LL |     let v = f;
+   |             ^ ambiguous name
+   |
+note: `f` could refer to the function imported here
+  --> $DIR/ambiguity-item.rs:6:5
+   |
+LL | use m::*;
+   |     ^^^^
+   = help: consider adding an explicit import of `f` to disambiguate
+note: `f` could also refer to the function imported here
+  --> $DIR/ambiguity-item.rs:11:5
+   |
+LL | use n::*; // OK, no conflict with `use m::*;`
+   |     ^^^^
+   = help: consider adding an explicit import of `f` to disambiguate
+
+error[E0659]: `f` is ambiguous (glob import vs glob import in the same module)
+  --> $DIR/ambiguity-item.rs:16:9
+   |
+LL |         f => {}
+   |         ^ ambiguous name
+   |
+note: `f` could refer to the function imported here
+  --> $DIR/ambiguity-item.rs:6:5
+   |
+LL | use m::*;
+   |     ^^^^
+   = help: consider adding an explicit import of `f` to disambiguate
+note: `f` could also refer to the function imported here
+  --> $DIR/ambiguity-item.rs:11:5
+   |
+LL | use n::*; // OK, no conflict with `use m::*;`
+   |     ^^^^
+   = help: consider adding an explicit import of `f` to disambiguate
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0659`.

src/test/ui/binding/const-param.rs

@@ -0,0 +1,12 @@
+// Identifier pattern referring to a const generic parameter is an error (issue #68853).
+
+#![feature(const_generics)] //~ WARN the feature `const_generics` is incomplete
+
+fn check<const N: usize>() {
+    match 1 {
+        N => {} //~ ERROR const parameters cannot be referenced in patterns
+        _ => {}
+    }
+}
+
+fn main() {}

src/test/ui/binding/const-param.stderr

@@ -0,0 +1,17 @@
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/const-param.rs:3:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0158]: const parameters cannot be referenced in patterns
+  --> $DIR/const-param.rs:7:9
+   |
+LL |         N => {}
+   |         ^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0158`.