From 3d9997889bfe536a96e70535ab208a6e7ff3bc12 Mon Sep 17 00:00:00 2001
From: David Lattimore <dml@google.com>
Date: Tue, 23 Jun 2020 19:07:42 +1000
Subject: SSR: Add initial support for placeholder constraints

---
 crates/ra_ssr/src/matching.rs | 39 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

(limited to 'crates/ra_ssr/src/matching.rs')

diff --git a/crates/ra_ssr/src/matching.rs b/crates/ra_ssr/src/matching.rs
index 53d802e77..ce53d46d2 100644
--- a/crates/ra_ssr/src/matching.rs
+++ b/crates/ra_ssr/src/matching.rs
@@ -2,7 +2,7 @@
 //! process of matching, placeholder values are recorded.
 
 use crate::{
-    parsing::{Placeholder, SsrTemplate},
+    parsing::{Constraint, NodeKind, Placeholder, SsrTemplate},
     SsrMatches, SsrPattern, SsrRule,
 };
 use hir::Semantics;
@@ -11,6 +11,7 @@ use ra_syntax::ast::{AstNode, AstToken};
 use ra_syntax::{ast, SyntaxElement, SyntaxElementChildren, SyntaxKind, SyntaxNode, SyntaxToken};
 use rustc_hash::FxHashMap;
 use std::{cell::Cell, iter::Peekable};
+use test_utils::mark;
 
 // Creates a match error. If we're currently attempting to match some code that we thought we were
 // going to match, as indicated by the --debug-snippet flag, then populate the reason field.
@@ -169,6 +170,9 @@ impl<'db, 'sema> MatchState<'db, 'sema> {
         if let Some(placeholder) =
             match_inputs.get_placeholder(&SyntaxElement::Node(pattern.clone()))
         {
+            for constraint in &placeholder.constraints {
+                self.check_constraint(constraint, code)?;
+            }
             if self.match_out.is_none() {
                 return Ok(());
             }
@@ -292,6 +296,24 @@ impl<'db, 'sema> MatchState<'db, 'sema> {
         Ok(())
     }
 
+    fn check_constraint(
+        &self,
+        constraint: &Constraint,
+        code: &SyntaxNode,
+    ) -> Result<(), MatchFailed> {
+        match constraint {
+            Constraint::Kind(kind) => {
+                kind.matches(code)?;
+            }
+            Constraint::Not(sub) => {
+                if self.check_constraint(&*sub, code).is_ok() {
+                    fail_match!("Constraint {:?} failed for '{}'", constraint, code.text());
+                }
+            }
+        }
+        Ok(())
+    }
+
     /// We want to allow the records to match in any order, so we have special matching logic for
     /// them.
     fn attempt_match_record_field_list(
@@ -515,6 +537,21 @@ impl SsrPattern {
     }
 }
 
+impl NodeKind {
+    fn matches(&self, node: &SyntaxNode) -> Result<(), MatchFailed> {
+        let ok = match self {
+            Self::Literal => {
+                mark::hit!(literal_constraint);
+                ast::Literal::can_cast(node.kind())
+            }
+        };
+        if !ok {
+            fail_match!("Code '{}' isn't of kind {:?}", node.text(), self);
+        }
+        Ok(())
+    }
+}
+
 // If `node` contains nothing but an ident then return it, otherwise return None.
 fn only_ident(element: SyntaxElement) -> Option<SyntaxToken> {
     match element {
-- 
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