Commits on Mar 27, 2021

1. Recover from if (let ...) in parsing, instead of lowering …

   When we recover from `if (let ...)` in lowering we can't "ungate" the
   syntax after generating the error
   
       invalid parentheses around `let` expression in `if let`
   
   as the feature_gate::check_crate pass has already run. This is mentioned
   in these comments in the old code
   
   > Ideally, we'd remove the feature gating of a `let` expression since we
   > are already complaining about it here, but `feature_gate::check_crate`
   > has already run by now
   
   We now recover from `if (let ...)` in parsing, generate the error as
   before, and "ungate" the syntax. For example, in this code:
   
       fn main() {
           let x = Some(3);
           if (let Some(y) = x) {}
       }
   
   We would previously generate:
   
       error[E0658]: `let` expressions in this position are experimental
        --> test.rs:3:9
         |
       3 |     if (let Some(y) = x) {}
         |         ^^^^^^^^^^^^^^^
         |
         = note: see issue rust-lang#53667 <rust-lang#53667> for more information
         = help: add `#![feature(let_chains)]` to the crate attributes to enable
         = help: you can write `matches!(<expr>, <pattern>)` instead of `let <pattern> = <expr>`
   
       error: invalid parentheses around `let` expression in `if let`
        --> test.rs:3:8
         |
       3 |     if (let Some(y) = x) {}
         |        ^               ^
         |
       help: `if let` needs to be written without parentheses
         |
       3 |     if let Some(y) = x {}
         |       --             --
   
       error: aborting due to 2 previous errors
   
   The first error doesn't make sense. With the "ungating" we now generate
   just the second one:
   
       error: invalid parentheses around `let` expression in `if let`
        --> test.rs:3:8
         |
       3 |     if (let Some(y) = x) {}
         |        ^               ^
         |
       help: `if let` needs to be written without parentheses
         |
       3 |     if let Some(y) = x {}
         |       --             --
   
       error: aborting due to previous error
   
   Fixes rust-lang#83274

   

   osa1 committed Mar 27, 2021
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   d23e0ed View commit details

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2. Refactor updating expr in parse_if_expr

   

   osa1 committed Mar 27, 2021
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   57363f4 View commit details

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