[fine] Many test improvements, error improvements

- Check for more error conditions
- Move to more definitive error assertions
- Simpler error messages in some cases
- Test more conditions more thoroughly, revisit old tests

fine/tests/expression/variable.fine

@@ -1,10 +1,15 @@
 let x = 23;
 let y = x * 2;
-let z = print(y);
+let z = y;
 z;
 
+fun test() -> f64 {
+  x + y
+}
+
 // @no-errors
-// @type: 41 f64
+// @type: 38 f64
+// @eval: Float(69.0)
 // @concrete:
 // | File
 // |   LetStatement
@@ -29,25 +34,38 @@ z;
 // |     Let:'"let"'
 // |     Identifier:'"z"'
 // |     Equal:'"="'
-// |     CallExpression
-// |       Identifier
-// |         Identifier:'"print"'
-// |       ArgumentList
-// |         LeftParen:'"("'
-// |         Argument
-// |           Identifier
-// |             Identifier:'"y"'
-// |         RightParen:'")"'
+// |     Identifier
+// |       Identifier:'"y"'
 // |     Semicolon:'";"'
 // |   ExpressionStatement
 // |     Identifier
 // |       Identifier:'"z"'
 // |     Semicolon:'";"'
+// |   FunctionDecl
+// |     Fun:'"fun"'
+// |     Identifier:'"test"'
+// |     ParamList
+// |       LeftParen:'"("'
+// |       RightParen:'")"'
+// |     ReturnType
+// |       Arrow:'"->"'
+// |       TypeExpression
+// |         Identifier:'"f64"'
+// |     Block
+// |       LeftBrace:'"{"'
+// |       ExpressionStatement
+// |         BinaryExpression
+// |           Identifier
+// |             Identifier:'"x"'
+// |           Plus:'"+"'
+// |           Identifier
+// |             Identifier:'"y"'
+// |       RightBrace:'"}"'
 // |
 // @compiles-to:
 // | function << module >> (0 args, 0 locals):
 // |   strings (0):
-// |   code (14):
+// |   code (12):
 // |     0: PushFloat(23.0)
 // |     1: StoreModule(0)
 // |     2: LoadModule(0)
@@ -55,11 +73,16 @@ z;
 // |     4: FloatMultiply
 // |     5: StoreModule(1)
 // |     6: LoadModule(1)
-// |     7: LoadExternFunction(0)
-// |     8: Call(1)
-// |     9: StoreModule(2)
-// |     10: LoadModule(2)
-// |     11: Discard
-// |     12: PushNothing
-// |     13: Return
+// |     7: StoreModule(2)
+// |     8: LoadModule(2)
+// |     9: Discard
+// |     10: PushNothing
+// |     11: Return
+// | function test (0 args, 0 locals):
+// |   strings (0):
+// |   code (4):
+// |     0: LoadModule(0)
+// |     1: LoadModule(1)
+// |     2: FloatAdd
+// |     3: Return
 // |