introduce hacks module

crates/ide_completion/src/completions/attribute.rs

@@ -309,7 +309,7 @@ fn parse_comma_sep_expr(input: ast::TokenTree) -> Option<Vec<ast::Expr>> {
         input_expressions
             .into_iter()
             .filter_map(|(is_sep, group)| (!is_sep).then(|| group))
-            .filter_map(|mut tokens| ast::Expr::parse(&tokens.join("")).ok())
+            .filter_map(|mut tokens| syntax::hacks::parse_expr_from_str(&tokens.join("")))
             .collect::<Vec<ast::Expr>>(),
     )
 }

crates/ide_completion/src/snippet.rs

@@ -212,15 +212,14 @@ fn validate_snippet(
 ) -> Option<(Box<[GreenNode]>, String, Option<Box<str>>)> {
     let mut imports = Vec::with_capacity(requires.len());
     for path in requires.iter() {
-        let path = ast::Path::parse(path).ok()?;
-        let valid_use_path = path.segments().all(|seg| {
-            matches!(seg.kind(), Some(ast::PathSegmentKind::Name(_)))
-                || seg.generic_arg_list().is_none()
-        });
-        if !valid_use_path {
+        let use_path = ast::SourceFile::parse(&format!("use {};", path))
+            .syntax_node()
+            .descendants()
+            .find_map(ast::Path::cast)?;
+        if use_path.syntax().text() != path.as_str() {
             return None;
         }
-        let green = path.syntax().green().into_owned();
+        let green = use_path.syntax().green().into_owned();
         imports.push(green);
     }
     let snippet = snippet.iter().join("\n");

crates/ide_db/src/helpers.rs

@@ -67,7 +67,11 @@ pub fn get_path_at_cursor_in_tt(cursor: &ast::Ident) -> Option<ast::Path> {
         .filter_map(SyntaxElement::into_token)
         .take_while(|tok| tok != cursor);
 
-    ast::Path::parse(&path_tokens.chain(iter::once(cursor.clone())).join("")).ok()
+    syntax::hacks::parse_expr_from_str(&path_tokens.chain(iter::once(cursor.clone())).join(""))
+        .and_then(|expr| match expr {
+            ast::Expr::PathExpr(it) => it.path(),
+            _ => None,
+        })
 }
 
 /// Parses and resolves the path at the cursor position in the given attribute, if it is a derive.
@@ -323,7 +327,12 @@ pub fn parse_tt_as_comma_sep_paths(input: ast::TokenTree) -> Option<Vec<ast::Pat
     let paths = input_expressions
         .into_iter()
         .filter_map(|(is_sep, group)| (!is_sep).then(|| group))
-        .filter_map(|mut tokens| ast::Path::parse(&tokens.join("")).ok())
+        .filter_map(|mut tokens| {
+            syntax::hacks::parse_expr_from_str(&tokens.join("")).and_then(|expr| match expr {
+                ast::Expr::PathExpr(it) => it.path(),
+                _ => None,
+            })
+        })
         .collect();
     Some(paths)
 }

crates/syntax/src/hacks.rs

@@ -0,0 +1,14 @@
+//! Things which exist to solve practial issues, but which shouldn't exist.
+//!
+//! Please avoid adding new usages of the functions in this module
+
+use crate::{ast, AstNode};
+
+pub fn parse_expr_from_str(s: &str) -> Option<ast::Expr> {
+    let file = ast::SourceFile::parse(&format!("const _: () = {};", s));
+    let expr = file.syntax_node().descendants().find_map(ast::Expr::cast)?;
+    if expr.syntax().text() != s {
+        return None;
+    }
+    Some(expr)
+}

crates/syntax/src/lib.rs

@@ -40,6 +40,7 @@ pub mod ast;
 pub mod fuzz;
 pub mod utils;
 pub mod ted;
+pub mod hacks;
 
 use std::{marker::PhantomData, sync::Arc};
 
@@ -167,26 +168,6 @@ impl SourceFile {
     }
 }
 
-// FIXME: `parse` functions shouldn't hang directly from AST nodes, and they
-// shouldn't return `Result`.
-//
-// We need a dedicated module for parser entry points, and they should always
-// return `Parse`.
-
-impl ast::Path {
-    /// Returns `text`, parsed as a path, but only if it has no errors.
-    pub fn parse(text: &str) -> Result<Self, ()> {
-        parsing::parse_text_as(text, parser::ParserEntryPoint::Path)
-    }
-}
-
-impl ast::Expr {
-    /// Returns `text`, parsed as an expression, but only if it has no errors.
-    pub fn parse(text: &str) -> Result<Self, ()> {
-        parsing::parse_text_as(text, parser::ParserEntryPoint::Expr)
-    }
-}
-
 /// Matches a `SyntaxNode` against an `ast` type.
 ///
 /// # Example:

crates/syntax/src/parsing.rs

@@ -5,7 +5,7 @@ mod reparsing;
 
 use rowan::TextRange;
 
-use crate::{syntax_node::GreenNode, AstNode, SyntaxError, SyntaxNode, SyntaxTreeBuilder};
+use crate::{syntax_node::GreenNode, SyntaxError, SyntaxTreeBuilder};
 
 pub(crate) use crate::parsing::reparsing::incremental_reparse;
 
@@ -17,26 +17,6 @@ pub(crate) fn parse_text(text: &str) -> (GreenNode, Vec<SyntaxError>) {
     (node, errors)
 }
 
-/// Returns `text` parsed as a `T` provided there are no parse errors.
-pub(crate) fn parse_text_as<T: AstNode>(
-    text: &str,
-    entry_point: parser::ParserEntryPoint,
-) -> Result<T, ()> {
-    let lexed = parser::LexedStr::new(text);
-    if lexed.errors().next().is_some() {
-        return Err(());
-    }
-    let parser_input = lexed.to_input();
-    let parser_output = parser::parse(&parser_input, entry_point);
-    let (node, errors, eof) = build_tree(lexed, parser_output, true);
-
-    if !errors.is_empty() || !eof {
-        return Err(());
-    }
-
-    SyntaxNode::new_root(node).first_child().and_then(T::cast).ok_or(())
-}
-
 pub(crate) fn build_tree(
     lexed: parser::LexedStr<'_>,
     parser_output: parser::Output,