[fine] Type testing with probes and reporting

I'm proud of the test harness here actually. Also fix a bug in
checking!

fine/tests/expression/arithmetic.fine

@@ -20,3 +20,5 @@
 // |     Semicolon:'";"'
 //
 1 * 2 + -3 * 4;
+
+// type: 532 f64

fine/tests/expression/boolean.fine

@@ -20,3 +20,5 @@
 // |     Semicolon:'";"'
 //
 true and false or false and !true;
+
+// type: 549 bool

fine/tests/expression/conditional.fine

@@ -24,3 +24,21 @@
 // |         RightBrace:'"}"'
 //
 if true { "discarded"; 23 } else { 45 }
+
+// Here come some type probes!
+// (type of the condition)
+// type: 667 bool
+//
+// (the discarded expression)
+// type: 674 string
+//
+// (the "then" clause)
+// type: 686 f64
+// type: 689 f64
+//
+// (the "else" clause)
+// type: 696 f64
+// type: 699 f64
+//
+// (the overall expression)
+// type: 664 f64

fine/tests/expression/number.fine

@@ -4,6 +4,7 @@
 // |     LiteralExpression
 // |       Number:'"42"'
 // |     Semicolon:'";"'
-//
-// type: 138 Number
+
 42;
+
+// type: 129 f64

fine/tests/expression/strings.fine

@@ -10,3 +10,5 @@
 // |     Semicolon:'";"'
 //
 "Hello " + 'world!';
+
+// type: 261 string