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Auto merge of #123007 - kadiwa4:suggest_convert_ptr_to_mut_ref, r=est…
…ebank Rework ptr-to-ref conversion suggestion for method calls If we have a value `z` of type `*const u8` and try to call `z.to_string()`, the upstream compiler will show you a note suggesting to call `<*const u8>::as_ref` first. This PR extends that: - The note will only be shown when the method would exist on the corresponding reference type - It can now suggest any of `<*const u8>::as_ref`, `<*mut u8>::as_ref` and `<*mut u8>::as_mut`, depending on what the method needs. I didn't introduce a `help` message because that's not a good idea with `unsafe` functions (and you'd also need to unwrap the `Option<&_>` somehow). People should check the safety requirements. For the simplest case ```rust fn main() { let x = 8u8; let z: *const u8 = &x; // issue #21596 println!("{}", z.to_string()); //~ ERROR E0599 } ``` the output changes like this: ```diff error[E0599]: `*const u8` doesn't implement `std::fmt::Display` --> $DIR/suggest-convert-ptr-to-ref.rs:5:22 | LL | println!("{}", z.to_string()); | ^^^^^^^^^ `*const u8` cannot be formatted with the default formatter | - = note: try using `<*const T>::as_ref()` to get a reference to the type behind the pointer: https://doc.rust-lang.org/std/primitive.pointer.html#method.as_ref - = note: using `<*const T>::as_ref()` on a pointer which is unaligned or points to invalid or uninitialized memory is undefined behavior +note: the method `to_string` exists on the type `&u8` + --> $SRC_DIR/alloc/src/string.rs:LL:COL + = note: try using the unsafe method `<*const T>::as_ref` to get an optional reference to the value behind the pointer: https://doc.rust-lang.org/std/primitive.pointer.html#method.as_ref = note: the following trait bounds were not satisfied: `*const u8: std::fmt::Display` which is required by `*const u8: ToString` ``` I removed the separate note about the safety requirements because it was incomplete and the linked doc page already has the information you need. Fixes #83695, but that's more of a side effect. The upstream compiler already suggests the right method name here.
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,17 @@ | ||
fn main() { | ||
let mut x = 8u8; | ||
let z: *const u8 = &x; | ||
// issue #21596 | ||
println!("{}", z.to_string()); //~ ERROR E0599 | ||
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let t: *mut u8 = &mut x; | ||
println!("{}", t.to_string()); //~ ERROR E0599 | ||
t.make_ascii_lowercase(); //~ ERROR E0599 | ||
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// suggest `as_mut` simply because the name is similar | ||
let _ = t.as_mut_ref(); //~ ERROR E0599 | ||
let _ = t.as_ref_mut(); //~ ERROR E0599 | ||
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// no ptr-to-ref suggestion | ||
z.make_ascii_lowercase(); //~ ERROR E0599 | ||
} |
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,70 @@ | ||
error[E0599]: `*const u8` doesn't implement `std::fmt::Display` | ||
--> $DIR/suggest-convert-ptr-to-ref.rs:5:22 | ||
| | ||
LL | println!("{}", z.to_string()); | ||
| ^^^^^^^^^ `*const u8` cannot be formatted with the default formatter | ||
| | ||
note: the method `to_string` exists on the type `&u8` | ||
--> $SRC_DIR/alloc/src/string.rs:LL:COL | ||
= note: you might want to use the unsafe method `<*const T>::as_ref` to get an optional reference to the value behind the pointer | ||
= note: read the documentation for `<*const T>::as_ref` and ensure you satisfy its safety preconditions before calling it to avoid undefined behavior: https://doc.rust-lang.org/std/primitive.pointer.html#method.as_ref | ||
= note: the following trait bounds were not satisfied: | ||
`*const u8: std::fmt::Display` | ||
which is required by `*const u8: ToString` | ||
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error[E0599]: `*mut u8` doesn't implement `std::fmt::Display` | ||
--> $DIR/suggest-convert-ptr-to-ref.rs:8:22 | ||
| | ||
LL | println!("{}", t.to_string()); | ||
| ^^^^^^^^^ `*mut u8` cannot be formatted with the default formatter | ||
| | ||
note: the method `to_string` exists on the type `&&mut u8` | ||
--> $SRC_DIR/alloc/src/string.rs:LL:COL | ||
= note: you might want to use the unsafe method `<*mut T>::as_ref` to get an optional reference to the value behind the pointer | ||
= note: read the documentation for `<*mut T>::as_ref` and ensure you satisfy its safety preconditions before calling it to avoid undefined behavior: https://doc.rust-lang.org/std/primitive.pointer.html#method.as_ref-1 | ||
= note: the following trait bounds were not satisfied: | ||
`*mut u8: std::fmt::Display` | ||
which is required by `*mut u8: ToString` | ||
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error[E0599]: no method named `make_ascii_lowercase` found for raw pointer `*mut u8` in the current scope | ||
--> $DIR/suggest-convert-ptr-to-ref.rs:9:7 | ||
| | ||
LL | t.make_ascii_lowercase(); | ||
| ^^^^^^^^^^^^^^^^^^^^ method not found in `*mut u8` | ||
| | ||
note: the method `make_ascii_lowercase` exists on the type `&mut u8` | ||
--> $SRC_DIR/core/src/num/mod.rs:LL:COL | ||
= note: you might want to use the unsafe method `<*mut T>::as_mut` to get an optional reference to the value behind the pointer | ||
= note: read the documentation for `<*mut T>::as_mut` and ensure you satisfy its safety preconditions before calling it to avoid undefined behavior: https://doc.rust-lang.org/std/primitive.pointer.html#method.as_mut | ||
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error[E0599]: no method named `as_mut_ref` found for raw pointer `*mut u8` in the current scope | ||
--> $DIR/suggest-convert-ptr-to-ref.rs:12:15 | ||
| | ||
LL | let _ = t.as_mut_ref(); | ||
| ^^^^^^^^^^ | ||
| | ||
help: there is a method `as_mut` with a similar name | ||
| | ||
LL | let _ = t.as_mut(); | ||
| ~~~~~~ | ||
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error[E0599]: no method named `as_ref_mut` found for raw pointer `*mut u8` in the current scope | ||
--> $DIR/suggest-convert-ptr-to-ref.rs:13:15 | ||
| | ||
LL | let _ = t.as_ref_mut(); | ||
| ^^^^^^^^^^ | ||
| | ||
help: there is a method `as_mut` with a similar name | ||
| | ||
LL | let _ = t.as_mut(); | ||
| ~~~~~~ | ||
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error[E0599]: no method named `make_ascii_lowercase` found for raw pointer `*const u8` in the current scope | ||
--> $DIR/suggest-convert-ptr-to-ref.rs:16:7 | ||
| | ||
LL | z.make_ascii_lowercase(); | ||
| ^^^^^^^^^^^^^^^^^^^^ method not found in `*const u8` | ||
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error: aborting due to 6 previous errors | ||
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For more information about this error, try `rustc --explain E0599`. |