Undefined variable never matches

3 files changed, 23 insertions, 2 deletions

diff --git a/effcee/check.cc b/effcee/check.cc
index d927994..28d9227 100644
--- a/effcee/check.cc
+++ b/effcee/check.cc
@@ -76,6 +76,11 @@ Check::Check(Type type, StringPiece param) : type_(type), param_(param) {
   parts_.push_back(make_unique<Check::Part>(Part::Type::Fixed, param));
 }
 
+bool Check::Part::MightMatch(const VarMapping& vars) const {
+  return type_ != Type::VarUse ||
+         vars.find(VarUseName().as_string()) != vars.end();
+}
+
 std::string Check::Part::Regex(const VarMapping& vars) const {
   switch (type_) {
     case Type::Fixed:
@@ -90,7 +95,7 @@ std::string Check::Part::Regex(const VarMapping& vars) const {
         // Return the escaped form of the current value of the variable.
         return RE2::QuoteMeta((*where).second);
       } else {
-        // The variable is not yet set.
+        // The variable is not yet set.  Should not get here.
         return "";
       }
     }
@@ -101,6 +106,9 @@ std::string Check::Part::Regex(const VarMapping& vars) const {
 bool Check::Matches(StringPiece* input, StringPiece* captured,
                     VarMapping* vars) const {
   if (parts_.empty()) return false;
+  for (auto& part : parts_) {
+    if (!part->MightMatch(*vars)) return false;
+  }
 
   std::unordered_map<int, std::string> var_def_indices;
 
diff --git a/effcee/check.h b/effcee/check.h
index fec0d80..005d00c 100644
--- a/effcee/check.h
+++ b/effcee/check.h
@@ -74,6 +74,10 @@ class Check {
           expression_(expr),
           num_capturing_groups_(CountCapturingGroups()) {}
 
+    // Returns true if this part might match a target string.  The only case where
+    // this is false is for a VarUse part where the variable is not yet defined.
+    bool MightMatch(const VarMapping& vars) const;
+
     // Returns a regular expression to match this part, given a mapping of
     // variable names to values.  If this part is a fixed string or variable use
     // then quoting has been applied.
diff --git a/effcee/match_test.cc b/effcee/match_test.cc
index 1824911..d1d0944 100644
--- a/effcee/match_test.cc
+++ b/effcee/match_test.cc
@@ -741,7 +741,7 @@ Begin
 }
 
 
-// TODO: Statefulness: variable definitions and uses
+// Statefulness: variable definitions and uses
 
 TEST(Match, VarDefFollowedByUse) {
   const auto result =
@@ -749,4 +749,13 @@ TEST(Match, VarDefFollowedByUse) {
   EXPECT_TRUE(result) << result.message();
 }
 
+TEST(Match, UndefinedVarNeverMatches) {
+  const auto result =
+      Match("Hello HeXllo", "CHECK: He[[X]]llo");
+  EXPECT_FALSE(result) << result.message();
+}
+
+
+// TODO: DAG def after use
+
 }  // namespace