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Allow e.g. if (cond) break/continue/return/kill; without brackets. #705

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Allow e.g. if (cond) break/continue/return/kill; without brackets. #705

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a4e85df
Allow e.g. `if (cond) break/continue/return/kill;`.
kdashg Apr 14, 2020
3045d14
Minor fixes.
kdashg May 15, 2020
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22 changes: 16 additions & 6 deletions wgsl/index.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -970,9 +970,24 @@ pipeline_stage
## Statements ## {#statements}

<pre class='def'>
branch_stmt
: RETURN logical_or_expression SEMICOLON
OpReturn
OpReturnValue
| break_stmt SEMICOLON
| continue_stmt SEMICOLON
| KILL SEMICOLON

body_stmt:
: BRACKET_LEFT statements BRACKET_RIGHT
| branch_stmt
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This seems to be too general as this makes it grammatically correct to say

fn foo() -> f32
   return 2.3;

Seems like we should have an if_body_stmt and then we need to update the if section so you can't do something like:

if (a)
  break;
else if (b)
  continue;
else
 kill;

as I don't think that should be allowed?

</pre>

While `body_stmt` is generally `{ statements }`, it also allows omitting brackets around some control-flow statements.
This can better preserve author intent for cases like `if (expr) break;`, where adding statements within the body block would have more semantic impact than expected.
`if (condition) { break/continue/return; }` is a common pattern where where the body block is unnecessary, since when the first statement branches/jumps, further statements in that block are unreachable.

<pre class='def'>
paren_rhs_stmt
: PAREN_LEFT logical_or_expression PAREN_RIGHT

Expand All @@ -981,17 +996,12 @@ statements

statement
: SEMICOLON
| RETURN logical_or_expression SEMICOLON
OpReturn
OpReturnValue
| branch_stmt
| if_stmt
| unless_stmt
| switch_stmt
| loop_stmt
| variable_stmt SEMICOLON
| break_stmt SEMICOLON
| continue_stmt SEMICOLON
| KILL SEMICOLON
| NOP SEMICOLON
| assignment_stmt SEMICOLON

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