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Emit fewer errors after parse errors #48724

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estebank opened this Issue Mar 4, 2018 · 0 comments

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estebank commented Mar 4, 2018

In cases of parse errors, many times we continue checking the code generating errors that would be fixed if the syntax was corrected. We should be more proactive in detecting elements that were "recovered" during parsing, in the same spirit as #46732.

It is particularly bad when encountering unenclosed delimiters. On this, the parser should try some really conservative local recovery (simple substitutions) and unless the rest of the code successfully compiles, the parser should discard the rest of the code until it finds a closing curly brace at the beggining of the line or EOF. This assumes that the likelihood of the following code being correct and usable is high. This type of recovery might still fail during typeck as, for example, methods might be missing. If this is the case, the impl block in the AST should be marked as "recovered" and during typeck avoid emitting errors related to it.

@estebank estebank added C-enhancement A-diagnostics A-parser labels Mar 4, 2018

@estebank estebank referenced this issue Dec 7, 2018

Closed

Gracefully handle missing comma between struct style enum variants #56579

@estebank estebank referenced this issue Jan 12, 2019

Merged

Modify some parser diagnostics to continue evaluating beyond the parser #57540

Centril added a commit to Centril/rust that referenced this issue Jan 14, 2019

@Centril
Rollup merge of rust-lang#57540 - estebank:eval-more, r=petrochenkov 
Modify some parser diagnostics to continue evaluating beyond the parser

Continue evaluating further errors after parser errors on:
 - trailing type argument attribute
 - lifetime in incorrect location
 - incorrect binary literal
 - missing `for` in `impl Trait for Foo`
 - type argument in `where` clause
 - incorrect float literal
 - incorrect `..` in pattern
 - associated types
 - incorrect discriminator value variant error

and others. All of these were found by making `continue-parse-after-error` `true` by default to identify errors that would need few changes. There are now only a handful of errors that have any change with `continue-parse-after-error` enabled.

These changes make it so `rust` _won't_ stop evaluation after finishing parsing, enabling type checking errors to be displayed on the existing code without having to fix the parse errors.

Each commit has an individual diagnostic change with their corresponding tests.

CC rust-lang#48724.
Verified
This commit was created on GitHub.com and signed with a verified signature using GitHub’s key.
GPG key ID: 4AEE18F83AFDEB23 Learn about signing commits
a8d0fc8

Centril added a commit to Centril/rust that referenced this issue Jan 14, 2019

@Centril
Rollup merge of rust-lang#57540 - estebank:eval-more, r=petrochenkov 
Modify some parser diagnostics to continue evaluating beyond the parser

Continue evaluating further errors after parser errors on:
 - trailing type argument attribute
 - lifetime in incorrect location
 - incorrect binary literal
 - missing `for` in `impl Trait for Foo`
 - type argument in `where` clause
 - incorrect float literal
 - incorrect `..` in pattern
 - associated types
 - incorrect discriminator value variant error

and others. All of these were found by making `continue-parse-after-error` `true` by default to identify errors that would need few changes. There are now only a handful of errors that have any change with `continue-parse-after-error` enabled.

These changes make it so `rust` _won't_ stop evaluation after finishing parsing, enabling type checking errors to be displayed on the existing code without having to fix the parse errors.

Each commit has an individual diagnostic change with their corresponding tests.

CC rust-lang#48724.
Verified
This commit was created on GitHub.com and signed with a verified signature using GitHub’s key.
GPG key ID: 4AEE18F83AFDEB23 Learn about signing commits
ce1f3e3

Centril added a commit to Centril/rust that referenced this issue Jan 14, 2019

@Centril
Rollup merge of rust-lang#57540 - estebank:eval-more, r=petrochenkov 
Modify some parser diagnostics to continue evaluating beyond the parser

Continue evaluating further errors after parser errors on:
 - trailing type argument attribute
 - lifetime in incorrect location
 - incorrect binary literal
 - missing `for` in `impl Trait for Foo`
 - type argument in `where` clause
 - incorrect float literal
 - incorrect `..` in pattern
 - associated types
 - incorrect discriminator value variant error

and others. All of these were found by making `continue-parse-after-error` `true` by default to identify errors that would need few changes. There are now only a handful of errors that have any change with `continue-parse-after-error` enabled.

These changes make it so `rust` _won't_ stop evaluation after finishing parsing, enabling type checking errors to be displayed on the existing code without having to fix the parse errors.

Each commit has an individual diagnostic change with their corresponding tests.

CC rust-lang#48724.
Verified
This commit was created on GitHub.com and signed with a verified signature using GitHub’s key.
GPG key ID: 4AEE18F83AFDEB23 Learn about signing commits
2f7a226
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