Give correct suggestion for a typo in raw pointers

compiler/rustc_parse/src/parser/ty.rs

@@ -398,6 +398,10 @@ impl<'a> Parser<'a> {
             // Qualified path
             let (qself, path) = self.parse_qpath(PathStyle::Type)?;
             TyKind::Path(Some(qself), path)
+        } else if (self.token.is_keyword(kw::Const) || self.token.is_keyword(kw::Mut))
+            && self.look_ahead(1, |t| *t == token::Star)
+        {
+            self.parse_ty_c_style_pointer()?
         } else if self.check_path() {
             self.parse_path_start_ty(lo, allow_plus, ty_generics)?
         } else if self.can_begin_bound() {
@@ -579,6 +583,41 @@ impl<'a> Parser<'a> {
         Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
     }
 
+    /// Parses a raw pointer with a C-style typo
+    fn parse_ty_c_style_pointer(&mut self) -> PResult<'a, TyKind> {
+        let kw_span = self.token.span;
+        let mutbl = self.parse_const_or_mut();
+
+        if let Some(mutbl) = mutbl
+            && self.eat(exp!(Star))
+        {
+            let star_span = self.prev_token.span;
+
+            let mutability = match mutbl {
+                Mutability::Not => "const",
+                Mutability::Mut => "mut",
+            };
+
+            let ty = self.parse_ty_no_question_mark_recover()?;
+
+            self.dcx()
+                .struct_span_err(
+                    kw_span,
+                    format!("raw pointer types must be written as `*{mutability} T`"),
+                )
+                .with_multipart_suggestion(
+                    format!("put the `*` before `{mutability}`"),
+                    vec![(star_span, String::new()), (kw_span.shrink_to_lo(), "*".to_string())],
+                    Applicability::MachineApplicable,
+                )
+                .emit();
+
+            return Ok(TyKind::Ptr(MutTy { ty, mutbl }));
+        }
+        // This is unreachable because we always get into if above and return from it
+        unreachable!("this could never happen")
+    }
+
     /// Parses a raw pointer type: `*[const | mut] $type`.
     fn parse_ty_ptr(&mut self) -> PResult<'a, TyKind> {
         let mutbl = self.parse_const_or_mut().unwrap_or_else(|| {

tests/ui/did_you_mean/c-style-pointer-types.fixed

@@ -0,0 +1,113 @@
+//@ run-rustfix
+
+#![allow(unused)]
+
+pub const P1: *const u8 = 0 as _;
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+pub const P2: *mut u8 = 1 as _;
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+pub const P3: *const i32 = std::ptr::null();
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+pub const P4: *const i32 = std::ptr::null();
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+pub const P5: *mut i32 = std::ptr::null_mut();
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+pub const P6: *mut i32 = std::ptr::null_mut();
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+pub const P7: *const Vec<u8> = std::ptr::null();
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+pub const P8: *const std::collections::HashMap<String, i32> = std::ptr::null();
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+fn func1(p: *const u8) {}
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+fn func2(p: *mut u8) {}
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+fn func3() -> *const u8 { std::ptr::null() }
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+fn func4() -> *mut u8 { std::ptr::null_mut() }
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+struct S1 {
+    field: *const u8,
+    //~^ ERROR: raw pointer types must be written as `*const T`
+    //~| HELP: put the `*` before `const`
+}
+
+struct S2 {
+    field: *mut u8,
+    //~^ ERROR: raw pointer types must be written as `*mut T`
+    //~| HELP: put the `*` before `mut`
+}
+
+type Tuple1 = (*const u8, i32);
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+type Tuple2 = (*mut u8, i32);
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+type Array1 = [*const u8; 10];
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+type Array2 = [*mut u8; 10];
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+type Alias1 = *const u8;
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+type Alias2 = *mut u8;
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+pub const P9: *const u8 = std::ptr::null();
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+pub const P10: *const    u8 = std::ptr::null();
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+impl S1 {
+    fn method(self, size: *const u32) {}
+    //~^ ERROR: raw pointer types must be written as `*const T`
+    //~| HELP: put the `*` before `const`
+}
+
+trait Trait1 {
+    fn method(p: *const u8);
+    //~^ ERROR: raw pointer types must be written as `*const T`
+    //~| HELP: put the `*` before `const`
+}
+
+fn generic_func<T>() -> *const T { std::ptr::null() }
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+fn main() {}

tests/ui/did_you_mean/c-style-pointer-types.rs

@@ -0,0 +1,113 @@
+//@ run-rustfix
+
+#![allow(unused)]
+
+pub const P1: const* u8 = 0 as _;
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+pub const P2: mut* u8 = 1 as _;
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+pub const P3: const* i32 = std::ptr::null();
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+pub const P4: const* i32 = std::ptr::null();
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+pub const P5: mut* i32 = std::ptr::null_mut();
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+pub const P6: mut* i32 = std::ptr::null_mut();
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+pub const P7: const* Vec<u8> = std::ptr::null();
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+pub const P8: const* std::collections::HashMap<String, i32> = std::ptr::null();
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+fn func1(p: const* u8) {}
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+fn func2(p: mut* u8) {}
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+fn func3() -> const* u8 { std::ptr::null() }
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+fn func4() -> mut* u8 { std::ptr::null_mut() }
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+struct S1 {
+    field: const* u8,
+    //~^ ERROR: raw pointer types must be written as `*const T`
+    //~| HELP: put the `*` before `const`
+}
+
+struct S2 {
+    field: mut* u8,
+    //~^ ERROR: raw pointer types must be written as `*mut T`
+    //~| HELP: put the `*` before `mut`
+}
+
+type Tuple1 = (const* u8, i32);
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+type Tuple2 = (mut* u8, i32);
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+type Array1 = [const* u8; 10];
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+type Array2 = [mut* u8; 10];
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+type Alias1 = const* u8;
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+type Alias2 = mut* u8;
+//~^ ERROR: raw pointer types must be written as `*mut T`
+//~| HELP: put the `*` before `mut`
+
+pub const P9: const *u8 = std::ptr::null();
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+pub const P10: const  *  u8 = std::ptr::null();
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+impl S1 {
+    fn method(self, size: const* u32) {}
+    //~^ ERROR: raw pointer types must be written as `*const T`
+    //~| HELP: put the `*` before `const`
+}
+
+trait Trait1 {
+    fn method(p: const* u8);
+    //~^ ERROR: raw pointer types must be written as `*const T`
+    //~| HELP: put the `*` before `const`
+}
+
+fn generic_func<T>() -> const* T { std::ptr::null() }
+//~^ ERROR: raw pointer types must be written as `*const T`
+//~| HELP: put the `*` before `const`
+
+fn main() {}