Encode def span for ConstParam

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -823,6 +823,7 @@ fn should_encode_span(def_kind: DefKind) -> bool {
         | DefKind::TraitAlias
         | DefKind::AssocTy
         | DefKind::TyParam
+        | DefKind::ConstParam
         | DefKind::Fn
         | DefKind::Const
         | DefKind::Static(_)
@@ -837,8 +838,7 @@ fn should_encode_span(def_kind: DefKind) -> bool {
         | DefKind::Impl { .. }
         | DefKind::Closure
         | DefKind::Generator => true,
-        DefKind::ConstParam
-        | DefKind::ExternCrate
+        DefKind::ExternCrate
         | DefKind::Use
         | DefKind::ForeignMod
         | DefKind::ImplTraitPlaceholder

tests/ui/consts/auxiliary/foreign-generic-mismatch-with-const-arg.rs

@@ -0,0 +1 @@
+pub fn test<const N: usize, T>() {}

tests/ui/consts/foreign-generic-mismatch-with-const-arg.rs

@@ -0,0 +1,8 @@
+// aux-build: foreign-generic-mismatch-with-const-arg.rs
+
+extern crate foreign_generic_mismatch_with_const_arg;
+
+fn main() {
+    foreign_generic_mismatch_with_const_arg::test::<1>();
+    //~^ ERROR function takes 2 generic arguments but 1 generic argument was supplied
+}

tests/ui/consts/foreign-generic-mismatch-with-const-arg.stderr

@@ -0,0 +1,21 @@
+error[E0107]: function takes 2 generic arguments but 1 generic argument was supplied
+  --> $DIR/foreign-generic-mismatch-with-const-arg.rs:6:46
+   |
+LL |     foreign_generic_mismatch_with_const_arg::test::<1>();
+   |                                              ^^^^   - supplied 1 generic argument
+   |                                              |
+   |                                              expected 2 generic arguments
+   |
+note: function defined here, with 2 generic parameters: `N`, `T`
+  --> $DIR/auxiliary/foreign-generic-mismatch-with-const-arg.rs:1:8
+   |
+LL | pub fn test<const N: usize, T>() {}
+   |        ^^^^ --------------  -
+help: add missing generic argument
+   |
+LL |     foreign_generic_mismatch_with_const_arg::test::<1, T>();
+   |                                                      +++
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0107`.