From b9d9db83d1ac85e83e018333f7aa4c5c5616e82b Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Tue, 10 Sep 2019 21:28:27 +0300
Subject: cleanup dollar handling in expressions

---
 crates/ra_parser/src/grammar/expressions.rs      | 49 +++++-------------------
 crates/ra_parser/src/grammar/expressions/atom.rs | 25 ++++++++++++
 2 files changed, 34 insertions(+), 40 deletions(-)

(limited to 'crates/ra_parser/src/grammar')

diff --git a/crates/ra_parser/src/grammar/expressions.rs b/crates/ra_parser/src/grammar/expressions.rs
index ea04b9458..1dd9a586c 100644
--- a/crates/ra_parser/src/grammar/expressions.rs
+++ b/crates/ra_parser/src/grammar/expressions.rs
@@ -14,20 +14,17 @@ const EXPR_FIRST: TokenSet = LHS_FIRST;
 
 pub(super) fn expr(p: &mut Parser) -> BlockLike {
     let r = Restrictions { forbid_structs: false, prefer_stmt: false };
-    let mut dollar_lvl = 0;
-    expr_bp(p, r, 1, &mut dollar_lvl).1
+    expr_bp(p, r, 1).1
 }
 
 pub(super) fn expr_stmt(p: &mut Parser) -> (Option<CompletedMarker>, BlockLike) {
     let r = Restrictions { forbid_structs: false, prefer_stmt: true };
-    let mut dollar_lvl = 0;
-    expr_bp(p, r, 1, &mut dollar_lvl)
+    expr_bp(p, r, 1)
 }
 
 fn expr_no_struct(p: &mut Parser) {
     let r = Restrictions { forbid_structs: true, prefer_stmt: false };
-    let mut dollar_lvl = 0;
-    expr_bp(p, r, 1, &mut dollar_lvl);
+    expr_bp(p, r, 1);
 }
 
 // test block
@@ -257,23 +254,8 @@ fn current_op(p: &Parser) -> (u8, SyntaxKind) {
 }
 
 // Parses expression with binding power of at least bp.
-fn expr_bp(
-    p: &mut Parser,
-    r: Restrictions,
-    mut bp: u8,
-    dollar_lvl: &mut usize,
-) -> (Option<CompletedMarker>, BlockLike) {
-    // `newly_dollar_open` is a flag indicated that dollar is just closed after lhs, e.g.
-    // `$1$ + a`
-    // We use this flag to skip handling it.
-    let mut newly_dollar_open = if p.at_l_dollar() {
-        *dollar_lvl += p.eat_l_dollars();
-        true
-    } else {
-        false
-    };
-
-    let mut lhs = match lhs(p, r, dollar_lvl) {
+fn expr_bp(p: &mut Parser, r: Restrictions, bp: u8) -> (Option<CompletedMarker>, BlockLike) {
+    let mut lhs = match lhs(p, r) {
         Some((lhs, blocklike)) => {
             // test stmt_bin_expr_ambiguity
             // fn foo() {
@@ -289,15 +271,6 @@ fn expr_bp(
     };
 
     loop {
-        if *dollar_lvl > 0 && p.at_r_dollar() {
-            *dollar_lvl -= p.eat_r_dollars(*dollar_lvl);
-            if !newly_dollar_open {
-                // We "pump" bp for make it highest priority
-                bp = 255;
-            }
-            newly_dollar_open = false;
-        }
-
         let is_range = p.at(T![..]) || p.at(T![..=]);
         let (op_bp, op) = current_op(p);
         if op_bp < bp {
@@ -306,7 +279,7 @@ fn expr_bp(
         let m = lhs.precede(p);
         p.bump(op);
 
-        expr_bp(p, r, op_bp + 1, dollar_lvl);
+        expr_bp(p, r, op_bp + 1);
         lhs = m.complete(p, if is_range { RANGE_EXPR } else { BIN_EXPR });
     }
     (Some(lhs), BlockLike::NotBlock)
@@ -314,11 +287,7 @@ fn expr_bp(
 
 const LHS_FIRST: TokenSet = atom::ATOM_EXPR_FIRST.union(token_set![AMP, STAR, EXCL, DOT, MINUS]);
 
-fn lhs(
-    p: &mut Parser,
-    r: Restrictions,
-    dollar_lvl: &mut usize,
-) -> Option<(CompletedMarker, BlockLike)> {
+fn lhs(p: &mut Parser, r: Restrictions) -> Option<(CompletedMarker, BlockLike)> {
     let m;
     let kind = match p.current() {
         // test ref_expr
@@ -351,7 +320,7 @@ fn lhs(
                     m = p.start();
                     p.bump(op);
                     if p.at_ts(EXPR_FIRST) {
-                        expr_bp(p, r, 2, dollar_lvl);
+                        expr_bp(p, r, 2);
                     }
                     return Some((m.complete(p, RANGE_EXPR), BlockLike::NotBlock));
                 }
@@ -367,7 +336,7 @@ fn lhs(
             return Some(postfix_expr(p, lhs, blocklike, !(r.prefer_stmt && blocklike.is_block())));
         }
     };
-    expr_bp(p, r, 255, dollar_lvl);
+    expr_bp(p, r, 255);
     Some((m.complete(p, kind), BlockLike::NotBlock))
 }
 
diff --git a/crates/ra_parser/src/grammar/expressions/atom.rs b/crates/ra_parser/src/grammar/expressions/atom.rs
index cea79cf6f..6e295fbf9 100644
--- a/crates/ra_parser/src/grammar/expressions/atom.rs
+++ b/crates/ra_parser/src/grammar/expressions/atom.rs
@@ -69,6 +69,7 @@ pub(super) fn atom_expr(p: &mut Parser, r: Restrictions) -> Option<(CompletedMar
     let done = match p.current() {
         T!['('] => tuple_expr(p),
         T!['['] => array_expr(p),
+        L_DOLLAR => meta_var_expr(p),
         T![|] => lambda_expr(p),
         T![move] if la == T![|] => lambda_expr(p),
         T![async] if la == T![|] || (la == T![move] && p.nth(2) == T![|]) => lambda_expr(p),
@@ -554,3 +555,27 @@ fn box_expr(p: &mut Parser, m: Option<Marker>) -> CompletedMarker {
     }
     m.complete(p, BOX_EXPR)
 }
+
+/// Expression from `$var` macro expansion, wrapped in dollars
+fn meta_var_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(L_DOLLAR));
+    let m = p.start();
+    p.bump(L_DOLLAR);
+    let (completed, _is_block) =
+        expr_bp(p, Restrictions { forbid_structs: false, prefer_stmt: false }, 1);
+
+    match (completed, p.current()) {
+        (Some(it), R_DOLLAR) => {
+            p.bump(R_DOLLAR);
+            m.abandon(p);
+            it
+        }
+        _ => {
+            while !p.at(R_DOLLAR) {
+                p.bump_any()
+            }
+            p.bump(R_DOLLAR);
+            m.complete(p, ERROR)
+        }
+    }
+}
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