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internal: more reasonable grammar for blocks

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Consider these expples

        { 92 }
  async { 92 }
    'a: { 92 }
   #[a] { 92 }

Previously the tree for them were

  BLOCK_EXPR
    { ... }

  EFFECT_EXPR
    async
    BLOCK_EXPR
      { ... }

  EFFECT_EXPR
    'a:
    BLOCK_EXPR
      { ... }

  BLOCK_EXPR
    #[a]
    { ... }

As you see, it gets progressively worse :) The last two items are
especially odd. The last one even violates the balanced curleys
invariant we have (#10357) The new approach is to say that the stuff in
`{}` is stmt_list, and the block is stmt_list + optional modifiers

  BLOCK_EXPR
    STMT_LIST
      { ... }

  BLOCK_EXPR
    async
    STMT_LIST
      { ... }

  BLOCK_EXPR
    'a:
    STMT_LIST
      { ... }

  BLOCK_EXPR
    #[a]
    STMT_LIST
      { ... }
This commit is contained in:
Aleksey Kladov 2021-09-26 12:12:57 +03:00
parent c51a3c78cf
commit 2bf81922f7
233 changed files with 11762 additions and 11343 deletions
Download patch file Download diff file Expand all files Collapse all files

36
crates/syntax/src/ast/expr_ext.rs
View file

@ -25,7 +25,6 @@ impl ast::Expr {
| ast::Expr::WhileExpr(_)
| ast::Expr::BlockExpr(_)
| ast::Expr::MatchExpr(_)
| ast::Expr::EffectExpr(_)
)
}
}
@ -268,38 +267,23 @@ impl ast::Literal {
}
}
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Effect {
pub enum BlockModifier {
Async(SyntaxToken),
Unsafe(SyntaxToken),
Try(SyntaxToken),
Const(SyntaxToken),
// Very much not an effect, but we stuff it into this node anyway
Label(ast::Label),
}
impl ast::EffectExpr {
pub fn effect(&self) -> Effect {
if let Some(token) = self.async_token() {
return Effect::Async(token);
}
if let Some(token) = self.unsafe_token() {
return Effect::Unsafe(token);
}
if let Some(token) = self.try_token() {
return Effect::Try(token);
}
if let Some(token) = self.const_token() {
return Effect::Const(token);
}
if let Some(label) = self.label() {
return Effect::Label(label);
}
unreachable!("ast::EffectExpr without Effect")
}
}
impl ast::BlockExpr {
pub fn modifier(&self) -> Option<BlockModifier> {
self.async_token()
.map(BlockModifier::Async)
.or_else(|| self.unsafe_token().map(BlockModifier::Unsafe))
.or_else(|| self.try_token().map(BlockModifier::Try))
.or_else(|| self.const_token().map(BlockModifier::Const))
.or_else(|| self.label().map(BlockModifier::Label))
}
/// false if the block is an intrinsic part of the syntax and can't be
/// replaced with arbitrary expression.
///
@ -312,7 +296,7 @@ impl ast::BlockExpr {
Some(it) => it,
None => return true,
};
!matches!(parent.kind(), FN | IF_EXPR | WHILE_EXPR | LOOP_EXPR | EFFECT_EXPR)
!matches!(parent.kind(), FN | IF_EXPR | WHILE_EXPR | LOOP_EXPR)
}
}