Rollup merge of rust-lang#78960 - ethanboxx:const-gen-test-default-error, r=lcnr

Test default values for const parameters.

The last topic on rust-lang#78433

I originally intended to place these tests in a single file, however, due to them being parser errors that are fatal, they must be in separate files to be detected.

Thanks, ``@lcnr`` for mentoring me on this PR.

r? ``@lcnr``

Author: GuillaumeGomez

src/test/ui/const-generics/min_const_generics/default_function_param.rs

@@ -0,0 +1,6 @@
+#![feature(min_const_generics)]
+
+fn foo<const SIZE: usize = 5>() {}
+                      //~^ ERROR expected one of `!`, `(`, `+`, `,`, `::`, `<`, or `>`, found `=`
+
+fn main() {}

src/test/ui/const-generics/min_const_generics/default_function_param.stderr

@@ -0,0 +1,8 @@
+error: expected one of `!`, `(`, `+`, `,`, `::`, `<`, or `>`, found `=`
+  --> $DIR/default_function_param.rs:3:26
+   |
+LL | fn foo<const SIZE: usize = 5>() {}
+   |                          ^ expected one of 7 possible tokens
+
+error: aborting due to previous error
+

src/test/ui/const-generics/min_const_generics/default_trait_param.rs

@@ -0,0 +1,6 @@
+#![feature(min_const_generics)]
+
+trait Foo<const KIND: bool = true> {}
+                        //~^ ERROR expected one of `!`, `(`, `+`, `,`, `::`, `<`, or `>`, found `=`
+
+fn main() {}

src/test/ui/const-generics/min_const_generics/default_trait_param.stderr

@@ -0,0 +1,8 @@
+error: expected one of `!`, `(`, `+`, `,`, `::`, `<`, or `>`, found `=`
+  --> $DIR/default_trait_param.rs:3:28
+   |
+LL | trait Foo<const KIND: bool = true> {}
+   |                            ^ expected one of 7 possible tokens
+
+error: aborting due to previous error
+