fix multiple eq bug

samples/infix/examples/multi_eq_bad.expected

@@ -0,0 +1,32 @@
+//! --expect-fail calculate
+//! --enable-tuples --expect-fail calculate
+//! --enable-tuples --tuples-require-parens --expect-fail calculate
+//! --enable-tuples --tuples-require-parens --use-parser-tuples --expect-fail calculate
+(top
+  {}
+  (infix-calculation
+    {
+      x = infix-assign}
+    (error
+      (errormsg 14:Invalid assign)
+      (errorast
+        (infix-equals
+          (group
+            (infix-ident 1:x))
+          (group
+            (infix-int 1:5))
+          (group
+            (infix-int 1:6)))))
+    (infix-assign
+      (infix-ident 1:x)
+      (infix-expression
+        (infix-int 1:1)))
+    (error
+      (errormsg 14:Invalid assign)
+      (errorast
+        (infix-equals
+          (group
+            (infix-ident 1:x))
+          (group)
+          (group
+            (infix-int 1:1)))))))

samples/infix/examples/multi_eq_bad.infix

@@ -0,0 +1,3 @@
+x = 5 = 6;
+x = 1 =; // this is not an error, surprisingly
+x = = 1;

samples/infix/examples/simple.infix

@@ -1,4 +1,4 @@
-x = 5 = 5;
+x = 5;
 print "x" x;
 y = 2 - 1;
 print "1 + 10" 1 + 10;

samples/infix/parse.cc

@@ -85,6 +85,8 @@ namespace infix
         R"([[:digit:]]+\b)" >> [](auto& m) { m.add(Int); },
 
         // Line comment.
+        // Note: care is taken to handle all 3 possible line endings: \n, \r,
+        // \r\n
         R"(//[^\n\r]*(\r\n?|\n))" >> [](auto&) {}, // another no-op
 
         // Print.

samples/infix/reader.cc

@@ -169,7 +169,7 @@ namespace
         // an Assign node that has two children: the Ident and the
         // an Expression, which will take the children of the Group.
         In(Calculation) *
-            (T(Equals) << ((T(Group) << T(Ident)[Id]) * T(Group)[Rhs])) >>
+            (T(Equals) << ((T(Group) << T(Ident)[Id]) * T(Group)[Rhs] * End)) >>
           [](Match& _) { return Assign << _(Id) << (Expression << *_[Rhs]); },
 
         // This rule selects a Group that matches the Output pattern