mGCA: drop literal anon-const special case in parser

Author: reddevilmidzy

compiler/rustc_parse/src/parser/path.rs

@@ -919,24 +919,10 @@ impl<'a> Parser<'a> {
         Ok((expr, mgca_disambiguation))
     }
 
-    /// Under `min_generic_const_args` we still allow *some* anon consts to be written without
-    /// a `const` block as it makes things quite a lot nicer. This function is useful for contexts
-    /// where we would like to use `MgcaDisambiguation::Direct` but need to fudge it to be `AnonConst`
-    /// in the presence of literals.
-    //
-    /// FIXME(min_generic_const_args): In the long term it would be nice to have a way to directly
-    /// represent literals in `hir::ConstArgKind` so that we can remove this special case by not
-    /// needing an anon const.
-    pub fn mgca_direct_lit_hack(&self, expr: &Expr) -> MgcaDisambiguation {
-        match &expr.kind {
-            ast::ExprKind::Lit(_) => MgcaDisambiguation::AnonConst,
-            ast::ExprKind::Unary(ast::UnOp::Neg, expr)
-                if matches!(expr.kind, ast::ExprKind::Lit(_)) =>
-            {
-                MgcaDisambiguation::AnonConst
-            }
-            _ => MgcaDisambiguation::Direct,
-        }
+    /// Under `min_generic_const_args`, prefer direct const arguments rather than
+    /// wrapping literals in anon consts.
+    pub fn mgca_direct_lit_hack(&self, _expr: &Expr) -> MgcaDisambiguation {
+        MgcaDisambiguation::Direct
     }
 
     /// Parse a generic argument in a path segment.

tests/ui/const-generics/associated-const-bindings/dyn-compat-self-const-projections-in-assoc-const-ty.stderr

@@ -1,27 +1,14 @@
-error[E0277]: the trait bound `FreshTy(0): A` is not satisfied
+error: type annotations needed for the literal
   --> $DIR/dyn-compat-self-const-projections-in-assoc-const-ty.rs:32:33
    |
 LL |     let _: dyn A<Ty = i32, CT = 0>;
-   |                                 ^ the trait `A` is not implemented for `FreshTy(0)`
-   |
-help: the trait `A` is implemented for `()`
-  --> $DIR/dyn-compat-self-const-projections-in-assoc-const-ty.rs:20:1
-   |
-LL | impl A for () {
-   | ^^^^^^^^^^^^^
+   |                                 ^
 
-error[E0277]: the trait bound `FreshTy(0): A` is not satisfied
+error: type annotations needed for the literal
   --> $DIR/dyn-compat-self-const-projections-in-assoc-const-ty.rs:34:34
    |
 LL |     let _: &dyn A<Ty = i32, CT = 0> = &();
-   |                                  ^ the trait `A` is not implemented for `FreshTy(0)`
-   |
-help: the trait `A` is implemented for `()`
-  --> $DIR/dyn-compat-self-const-projections-in-assoc-const-ty.rs:20:1
-   |
-LL | impl A for () {
-   | ^^^^^^^^^^^^^
+   |                                  ^
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0277`.

tests/ui/const-generics/mgca/array-expr-type-mismatch-in-where-bound.rs

@@ -14,7 +14,7 @@ where
 
 fn bar<T>()
 where
-    T: Trait2<3>, //~ ERROR: mismatched types
+    T: Trait2<3>, //~ ERROR: type annotations needed for the literal
 {
 }
 

tests/ui/const-generics/mgca/array-expr-type-mismatch-in-where-bound.stderr

@@ -4,12 +4,11 @@ error: expected `usize`, found const array
 LL |     T: Trait1<{ [] }>,
    |                 ^^
 
-error[E0308]: mismatched types
+error: type annotations needed for the literal
   --> $DIR/array-expr-type-mismatch-in-where-bound.rs:17:15
    |
 LL |     T: Trait2<3>,
-   |               ^ expected `[u8; 3]`, found integer
+   |               ^
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0308`.

tests/ui/const-generics/mgca/type_const-inherent-const-omitted-type.rs

@@ -6,6 +6,7 @@ struct A;
 impl A {
     type const B = 4;
     //~^ ERROR: missing type for `const` item
+    //~| ERROR: type annotations needed for the literal
 }
 
 fn main() {}

tests/ui/const-generics/mgca/type_const-inherent-const-omitted-type.stderr

@@ -9,5 +9,11 @@ help: provide a type for the item
 LL |     type const B: <type> = 4;
    |                 ++++++++
 
-error: aborting due to 1 previous error
+error: type annotations needed for the literal
+  --> $DIR/type_const-inherent-const-omitted-type.rs:7:20
+   |
+LL |     type const B = 4;
+   |                    ^
+
+error: aborting due to 2 previous errors
 

tests/ui/const-generics/mgca/type_const-mismatched-types.rs

@@ -3,7 +3,6 @@
 
 type const FREE: u32 = 5_usize;
 //~^ ERROR the constant `5` is not of type `u32`
-//~| ERROR mismatched types
 
 type const FREE2: isize = FREE;
 //~^ ERROR the constant `5` is not of type `isize`
@@ -14,7 +13,7 @@ trait Tr {
 
 impl Tr for () {
     type const N: usize = false;
-    //~^ ERROR mismatched types
+    //~^ ERROR the constant `false` is not of type `usize`
 }
 
 fn main() {}

tests/ui/const-generics/mgca/type_const-mismatched-types.stderr

@@ -5,29 +5,16 @@ LL | type const FREE: u32 = 5_usize;
    | ^^^^^^^^^^^^^^^^^^^^ expected `u32`, found `usize`
 
 error: the constant `5` is not of type `isize`
-  --> $DIR/type_const-mismatched-types.rs:8:1
+  --> $DIR/type_const-mismatched-types.rs:7:1
    |
 LL | type const FREE2: isize = FREE;
    | ^^^^^^^^^^^^^^^^^^^^^^^ expected `isize`, found `usize`
 
-error[E0308]: mismatched types
-  --> $DIR/type_const-mismatched-types.rs:16:27
+error: the constant `false` is not of type `usize`
+  --> $DIR/type_const-mismatched-types.rs:15:5
    |
 LL |     type const N: usize = false;
-   |                           ^^^^^ expected `usize`, found `bool`
+   |     ^^^^^^^^^^^^^^^^^^^ expected `usize`, found `bool`
 
-error[E0308]: mismatched types
-  --> $DIR/type_const-mismatched-types.rs:4:24
-   |
-LL | type const FREE: u32 = 5_usize;
-   |                        ^^^^^^^ expected `u32`, found `usize`
-   |
-help: change the type of the numeric literal from `usize` to `u32`
-   |
-LL - type const FREE: u32 = 5_usize;
-LL + type const FREE: u32 = 5_u32;
-   |
-
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0308`.

tests/ui/const-generics/mgca/type_const-only-in-impl-omitted-type.rs

@@ -10,6 +10,7 @@ struct GoodS;
 impl BadTr for GoodS {
     type const NUM: = 84;
     //~^ ERROR: missing type for `const` item
+    //~| ERROR: type annotations needed for the literal
 
 }
 

tests/ui/const-generics/mgca/type_const-only-in-impl-omitted-type.stderr

@@ -5,12 +5,18 @@ LL |     type const NUM: = 84;
    |                    ^ help: provide a type for the associated constant: `usize`
 
 error: use of trait associated const not defined as `type const`
-  --> $DIR/type_const-only-in-impl-omitted-type.rs:16:43
+  --> $DIR/type_const-only-in-impl-omitted-type.rs:17:43
    |
 LL | fn accept_bad_tr<const N: usize, T: BadTr<NUM = { N }>>(_x: &T) {}
    |                                           ^^^^^^^^^^^
    |
    = note: the declaration in the trait must begin with `type const` not just `const` alone
 
-error: aborting due to 2 previous errors
+error: type annotations needed for the literal
+  --> $DIR/type_const-only-in-impl-omitted-type.rs:11:23
+   |
+LL |     type const NUM: = 84;
+   |                       ^^
+
+error: aborting due to 3 previous errors