Previously whenever a duplicate discriminant was detected for an Enum,
we would print the discriminant bits in the diagnostic without any
casting. This caused us to display incorrect values for negative
discriminants. After this PR we format the discriminant signedness
correctly. Also reworded some of the original error
messages.
Remove mutable_borrow_reservation_conflict lint and allow the code pattern
This was the only breaking issue with the NLL stabilization PR. Lang team decided to go ahead and allow this.
r? `@nikomatsakis`
Closes#59159Closes#56254
Erase type params when suggesting fully qualified path
When suggesting the use of a fully qualified path for a method call that
is ambiguous because it has multiple candidates, erase type params in
the resulting code, as they would result in an error when applied. We
replace them with `_` in the output to rely on inference. There might be
cases where this still produces slighlty incomplete suggestions, but it
otherwise produces many more errors in relatively common cases.
Fix#96292
This attempts to bring better error messages to invalid method calls, by applying some heuristics to identify common mistakes.
The algorithm is inspired by Levenshtein distance and longest common sub-sequence. In essence, we treat the types of the function, and the types of the arguments you provided as two "words" and compute the edits to get from one to the other.
We then modify that algorithm to detect 4 cases:
- A function input is missing
- An extra argument was provided
- The type of an argument is straight up invalid
- Two arguments have been swapped
- A subset of the arguments have been shuffled
(We detect the last two as separate cases so that we can detect two swaps, instead of 4 parameters permuted.)
It helps to understand this argument by paying special attention to terminology: "inputs" refers to the inputs being *expected* by the function, and "arguments" refers to what has been provided at the call site.
The basic sketch of the algorithm is as follows:
- Construct a boolean grid, with a row for each argument, and a column for each input. The cell [i, j] is true if the i'th argument could satisfy the j'th input.
- If we find an argument that could satisfy no inputs, provided for an input that can't be satisfied by any other argument, we consider this an "invalid type".
- Extra arguments are those that can't satisfy any input, provided for an input that *could* be satisfied by another argument.
- Missing inputs are inputs that can't be satisfied by any argument, where the provided argument could satisfy another input
- Swapped / Permuted arguments are identified with a cycle detection algorithm.
As each issue is found, we remove the relevant inputs / arguments and check for more issues. If we find no issues, we match up any "valid" arguments, and start again.
Note that there's a lot of extra complexity:
- We try to stay efficient on the happy path, only computing the diagonal until we find a problem, and then filling in the rest of the matrix.
- Closure arguments are wrapped in a tuple and need to be unwrapped
- We need to resolve closure types after the rest, to allow the most specific type constraints
- We need to handle imported C functions that might be variadic in their inputs.
I tried to document a lot of this in comments in the code and keep the naming clear.
Extends support for generating `DiagnosticMessage::FluentIdentifier`
messages from `SessionDiagnostic` derive to `#[label]`.
Signed-off-by: David Wood <david.wood@huawei.com>
This makes the order of the output always consistent:
1. Place of the `match` missing arms
2. The `enum` definition span
3. The structured suggestion to add a fallthrough arm
* Point at RHS of associated type in obligation span
* Point at `impl` assoc type on projection error
* Reduce verbosity of recursive obligations
* Point at source of binding lifetime obligation
* Tweak "required bound" note
* Tweak "expected... found opaque (return) type" labels
* Point at set type in impl assoc type WF errors
* Do not emit unnecessary E0308 after E0070
* Show fewer errors on `while let` missing `let`
* Hide redundant E0308 on `while let` missing `let`
* Point at binding definition when possible on invalid assignment
* do not point at closure twice
* do not suggest `if let` for literals in lhs
* account for parameter types
