Add fix to error msg which relied on order

Previously types needed to be ordered before consts. Since relaxing that restriction, this
created a bug wherever relying on that. This produces a strange error message, so it's not awful
but should still be fixed.

Add ParamKindOrd instead of &str

Switches from using strings to ParamKindOrd, as dealing with enums provides better guarantees to
not miss things.

Add test

Add new loop for checking types/consts

Update to check const & type in 1 loop

Author: JulianKnodt

compiler/rustc_middle/src/ty/mod.rs

@@ -826,6 +826,8 @@ pub struct GenericParamCount {
     pub lifetimes: usize,
     pub types: usize,
     pub consts: usize,
+
+    pub type_defaults: usize,
 }
 
 /// Information about the formal type/lifetime parameters associated
@@ -861,7 +863,10 @@ impl<'tcx> Generics {
         for param in &self.params {
             match param.kind {
                 GenericParamDefKind::Lifetime => own_counts.lifetimes += 1,
-                GenericParamDefKind::Type { .. } => own_counts.types += 1,
+                GenericParamDefKind::Type { has_default, .. } => {
+                    own_counts.types += 1;
+                    own_counts.type_defaults += has_default as usize;
+                }
                 GenericParamDefKind::Const => own_counts.consts += 1,
             };
         }

compiler/rustc_typeck/src/astconv/generics.rs

@@ -0,0 +1,88 @@
+// Check that ordering of errors is correctly reported even with consts preceding types.
+
+#![feature(const_generics)]
+#![allow(incomplete_features)]
+
+struct Example<'a, const N: usize, T=f32> {
+  s: &'a T,
+}
+
+type Consts = Example<3, 3, 3>;
+//~^ ERROR missing lifetime specifier
+//~| ERROR wrong number of const arguments
+type Types = Example<f32, f32, f32>;
+//~^ ERROR missing lifetime specifier
+//~| ERROR wrong number of const arguments
+//~| ERROR wrong number of type arguments
+type Lifetimes = Example<'static, 'static, 'static>;
+//~^ ERROR wrong number of const arguments
+//~| ERROR misplaced type arguments
+//~| wrong number of lifetime
+
+type LtConst1 = Example<'static, 3, 3>;
+//~^ ERROR wrong number of const arguments
+type LtConst2 = Example<3, 'static, 3>;
+//~^ ERROR wrong number of const arguments
+type LtConst3 = Example<3, 3, 'static>;
+//~^ ERROR misplaced type arguments
+
+type LtTy1 = Example<'static, f32, f32>;
+//~^ ERROR wrong number of const arguments
+//~| ERROR wrong number of type arguments
+type LtTy2 = Example<f32, 'static, f32>;
+//~^ ERROR wrong number of const arguments
+//~| ERROR wrong number of type arguments
+type LtTy3 = Example<f32, f32, 'static>;
+//~^ ERROR wrong number of const arguments
+//~| ERROR wrong number of type arguments
+
+type ConstTy1 = Example<3, f32, f32>;
+//~^ ERROR missing lifetime specifier
+//~| ERROR wrong number of type arguments
+type ConstTy2 = Example<f32, 3, f32>;
+//~^ ERROR missing lifetime specifier
+//~| ERROR wrong number of type arguments
+type ConstTy3 = Example<f32, f32, 3>;
+//~^ ERROR missing lifetime specifier
+//~| ERROR wrong number of type arguments
+
+type ConstLt1 = Example<3, 'static, 'static>;
+//~^ ERROR wrong number of lifetime
+type ConstLt2 = Example<'static, 3, 'static>;
+//~^ ERROR wrong number of lifetime
+type ConstLt3 = Example<'static, 'static, 3>;
+//~^ ERROR wrong number of lifetime
+
+type TyLt1 = Example<f32, 'static, 'static>;
+//~^ ERROR wrong number of lifetime
+//~| ERROR wrong number of const
+//~| ERROR misplaced type arguments
+type TyLt2 = Example<'static, f32, 'static>;
+//~^ ERROR wrong number of lifetime
+//~| ERROR wrong number of const
+//~| ERROR misplaced type arguments
+type TyLt3 = Example<'static, 'static, f32>;
+//~^ ERROR wrong number of const
+//~| ERROR wrong number of lifetime
+
+type TyConst1 = Example<f32, 3, 3>;
+//~^ ERROR missing lifetime specifier
+//~| ERROR wrong number of const
+//~| ERROR misplaced type arguments
+type TyConst2 = Example<3, f32, 3>;
+//~^ ERROR missing lifetime specifier
+//~| ERROR wrong number of const
+type TyConst3 = Example<3, 3, f32>;
+//~^ ERROR missing lifetime specifier
+//~| ERROR wrong number of const
+//~| ERROR misplaced type arguments
+
+type Intermixed1 = Example<'static, 3, f32>; // ok
+
+
+type Intermixed2 = Example<f32, 'static, 3>;
+//~^ ERROR type provided when a constant was expected
+type Intermixed3 = Example<3, f32, 'static>;
+//~^ ERROR constant provided when a lifetime
+
+fn main() {}