Fix import errors in multi-methods (#223)

* Fix the litany of errors that occurred in diagnosing multi-methods

* Rectify test failures

Author: chrisrink10

src/basilisp/compiler.py

@@ -965,7 +965,7 @@ def _import_ast(ctx: CompilerContext, form: llist.List) -> ASTStream:
 
 def _interop_call_ast(ctx: CompilerContext, form: llist.List) -> ASTStream:
     """Generate a Python AST node for Python interop method calls."""
-    assert form[0] == _INTEROP_CALL
+    assert form.first == _INTEROP_CALL
     assert form[1] is not None
     assert isinstance(form[2], sym.Symbol)
     assert form[2] is not None
@@ -987,7 +987,7 @@ def _interop_call_ast(ctx: CompilerContext, form: llist.List) -> ASTStream:
 
 def _interop_prop_ast(ctx: CompilerContext, form: llist.List) -> ASTStream:
     """Generate a Python AST node for Python interop property access."""
-    assert form[0] == _INTEROP_PROP
+    assert form.first == _INTEROP_PROP
     assert form[1] is not None
     assert isinstance(form[2], sym.Symbol)
     assert form[2].ns is None
@@ -1020,7 +1020,7 @@ def let_32(a_33, b_34, c_35):
 
         let_32(a_36, b_37, c_38)  #=> {:length 1}
     """
-    assert form[0] == _LET
+    assert form.first == _LET
     assert isinstance(form[1], vec.Vector)
     assert len(form) >= 3
 

src/basilisp/core/__init__.lpy

@@ -1385,14 +1385,14 @@
                       body)
         dispatch-fn (first body)
         opts        (apply hash-map (rest body))]
-    `(def ~name (basilisp.lang.multifn/MultiFunction ~name
+    `(def ~name (basilisp.lang.multifn/MultiFunction ~(quote name)
                                                      ~dispatch-fn
-                                                     (or (:default opts) :default)))))
+                                                     ~(or (:default opts) :default)))))
 
 (defmacro defmethod
   "Add a new method to the multi-function which responds to dispatch-val."
   [multifn dispatch-val & fn-tail]
-  `(.add-method multi-fn dispatch-val (fn ~@fn-tail)))
+  `(. ~multifn ~'add-method ~dispatch-val (fn ~@fn-tail)))
 
 (defn methods
   "Return a map of dispatch values to methods for the given multi function."
@@ -1414,6 +1414,6 @@
 
 (defn remove-all-methods
   "Remove all method for this multi-function. Return the multi function."
-  [multifn dispatch-val]
+  [multifn]
   (.remove-all-methods multifn)
   multifn)

src/basilisp/lang/runtime.py

@@ -239,6 +239,7 @@ class Namespace:
                                               'basilisp.lang.keyword',
                                               'basilisp.lang.list',
                                               'basilisp.lang.map',
+                                              'basilisp.lang.multifn',
                                               'basilisp.lang.runtime',
                                               'basilisp.lang.seq',
                                               'basilisp.lang.set',

tests/basilisp/test_multifn.lpy

@@ -0,0 +1,46 @@
+(ns basilisp.multifn-test
+  (:require
+   [basilisp.test :refer [deftest is testing]]))
+
+(defmulti test-fn
+  (fn [v]
+    (cond
+      (= v "i")  :a
+      (= v "ii") :b
+      :else      :default)))
+
+(defmethod test-fn :a
+  [_]
+  "1")
+
+(defmethod test-fn :b
+  [_]
+  "2")
+
+(defmethod test-fn :default
+  [_]
+  "BLAH")
+
+(deftest test-multi-functions
+  (testing "multi method usage"
+    (is (= "1" (test-fn "i")))
+    (is (= "2" (test-fn "ii")))
+    (is (= "BLAH" (test-fn "iii")))
+    (is (= "BLAH" (test-fn "other"))))
+
+  (testing "multi-method generic assertions"
+    (is (map? (methods test-fn)))
+    (is (seq (methods test-fn))))
+
+  (testing "multi method usage after removal"
+    (remove-method test-fn :b)
+
+    (is (= "1" (test-fn "i")))
+    (is (= "BLAH" (test-fn "ii")))
+    (is (= "BLAH" (test-fn "iii")))
+    (is (= "BLAH" (test-fn "other"))))
+
+  (testing "removing all methods"
+    (remove-all-methods test-fn)
+
+    (is (not (seq (methods test-fn))))))