- Made some improvements to error messages in the compiler.

26 files changed, 144 insertions, 128 deletions

diff --git a/luxc/src/lux.clj b/luxc/src/lux.clj
index 2daf0000a..3ca520576 100644
--- a/luxc/src/lux.clj
+++ b/luxc/src/lux.clj
@@ -31,4 +31,4 @@
                 target-dir)
 
     _
-    (println "Can't understand command.")))
+    (println "Cannot understand command.")))
diff --git a/luxc/src/lux/analyser.clj b/luxc/src/lux/analyser.clj
index aaf441713..4090cfea8 100644
--- a/luxc/src/lux/analyser.clj
+++ b/luxc/src/lux/analyser.clj
@@ -197,7 +197,7 @@
             (&&lux/analyse-apply analyse cursor exo-type macro-caller =fn parameters))))
       
       _
-      (&/fail-with-loc (str "[Analyser Error] Unknown syntax: " (prn-str (&/show-ast (&/T [(&/T ["" -1 -1]) token])))))
+      (&/fail-with-loc (str "[Analyser Error] Unknown syntax: " (&/show-ast (&/T [(&/T ["" -1 -1]) token]))))
       )))
 
 ;; [Resources]
diff --git a/luxc/src/lux/analyser/base.clj b/luxc/src/lux/analyser/base.clj
index 3f95e072a..f4718a67e 100644
--- a/luxc/src/lux/analyser/base.clj
+++ b/luxc/src/lux/analyser/base.clj
@@ -55,7 +55,7 @@
       (return x)
 
       _
-      (&/fail-with-loc "[Analyser Error] Can't expand to other than 1 element."))))
+      (&/fail-with-loc "[Analyser Error] Macro cannot expand to more than 1 output."))))
 
 (defn analyse-1 [analyse exo-type elem]
   (&/with-expected-type exo-type
diff --git a/luxc/src/lux/analyser/case.clj b/luxc/src/lux/analyser/case.clj
index a37b6ebf3..5b25115ea 100644
--- a/luxc/src/lux/analyser/case.clj
+++ b/luxc/src/lux/analyser/case.clj
@@ -180,7 +180,7 @@
       (apply-type! =type-fun param))
     
     _
-    (&/fail-with-loc (str "[Type System] Not a type function:\n" (&type/show-type type-fn) "\n"))))
+    (&/fail-with-loc (str "[Type System] Not a type-function:\n" (&type/show-type type-fn) "\n"))))
 
 (defn adjust-type* [up type]
   "(-> (List (, (Maybe (List Type)) Int Type)) Type (Lux Type))"
@@ -245,7 +245,7 @@
     (return type)
 
     _
-    (&/fail-with-loc (str "[Pattern-matching Error] Can't adjust type: " (&type/show-type type)))
+    (&/fail-with-loc (str "[Pattern-matching Error] Cannot pattern-match against type: " (&type/show-type type)))
     ))
 
 (defn adjust-type [type]
@@ -335,9 +335,10 @@
                                                (return (&/T [&/$Nil =kont])))
                                              (&/|reverse (&/zip2 _tuple-types ?members)))]
                   (return (&/T [($TupleTestAC =tests) =kont])))
-                (&/fail-with-loc (str "[Pattern-matching Error] Pattern-matching mismatch. Require tuple[" (&/|length (&type/flatten-prod value-type*)) "]. Given tuple [" (&/|length ?members) "]"
-                                      " -- " (&/show-ast pattern)
-                                      " " (&type/show-type value-type*) " " (&type/show-type value-type)))))
+                (&/fail-with-loc (str "[Pattern-matching Error] Pattern-matching mismatch. Requires tuple[" (&/|length (&type/flatten-prod value-type*)) "]. Given tuple [" (&/|length ?members) "].\n"
+                                      "           At: " (&/show-ast pattern) "\n"
+                                      "Expected type: " (&type/show-type value-type*) "\n"
+                                      "  Actual type: " (&type/show-type value-type)))))
 
             _
             (&/fail-with-loc (str "[Pattern-matching Error] Tuples require tuple-types: " (&type/show-type value-type))))))
@@ -523,7 +524,9 @@
                                  (merge-total v (&/T [t ?body])))
                                ?values ?tests)]
           (return ($TupleTotal total? structs)))
-        (&/fail-with-loc "[Pattern-matching Error] Inconsistent tuple-size."))
+        (&/fail-with-loc (str "[Pattern-matching Error] Inconsistent tuple-size.\n"
+                              "Expected: " (&/|length ?values) "\n"
+                              "  Actual: " (&/|length ?tests))))
 
       [($DefaultTotal total?) ($VariantTestAC ?tag ?count ?test)]
       (|do [sub-struct (merge-total ($DefaultTotal total?)
@@ -533,7 +536,7 @@
                       (return list)
 
                       (&/$None)
-                      (&/fail-with-loc "[Pattern-matching Error] YOLO"))]
+                      (assert false))]
         (return ($VariantTotal total? structs)))
 
       [($VariantTotal total? ?branches) ($VariantTestAC ?tag ?count ?test)]
@@ -549,7 +552,7 @@
                       (return list)
 
                       (&/$None)
-                      (&/fail-with-loc "[Pattern-matching Error] YOLO"))]
+                      (assert false))]
         (return ($VariantTotal total? structs)))
       )))
 
@@ -623,11 +626,11 @@
               (|case value-type*
                 (&/$ProdT _)
                 (|let [num-elems (&/|length ?structs)
-                       [_shorter _tuple-types] (&type/tuple-types-for (&/|length ?structs) value-type*)]
-                  (if (= num-elems _shorter)
-                    (|do [totals (&/map2% check-totality _tuple-types ?structs)]
-                      (return (&/fold #(and %1 %2) true totals)))
-                    (&/fail-with-loc (str "[Pattern-maching Error] Tuple-mismatch. Require tuple[" (&/|length (&type/flatten-prod value-type*)) "]. Given tuple [" (&/|length ?structs) "]"))))
+                       [_shorter _tuple-types] (&type/tuple-types-for (&/|length ?structs) value-type*)
+                       _ (&/assert! (= num-elems _shorter)
+                                    (&/fail-with-loc (str "[Pattern-maching Error] Tuple-mismatch. Require tuple[" (&/|length (&type/flatten-prod value-type*)) "]. Given tuple [" (&/|length ?structs) "]")))]
+                  (|do [totals (&/map2% check-totality _tuple-types ?structs)]
+                    (return (&/fold #(and %1 %2) true totals))))
                 
                 _
                 (&/fail-with-loc (str "[Pattern-maching Error] Tuple is not total." " - " (&type/show-type value-type*)))))))))
@@ -655,7 +658,6 @@
                           &/$Nil
                           branches)
         struct (&/fold% merge-total ($DefaultTotal false) patterns)
-        ? (check-totality value-type struct)]
-    (if ?
-      (return patterns)
-      (&/fail-with-loc "[Pattern-maching Error] Pattern-matching is non-total."))))
+        ? (check-totality value-type struct)
+        _ (&/assert! ? "[Pattern-maching Error] Pattern-matching is not total.")]
+    (return patterns)))
diff --git a/luxc/src/lux/analyser/env.clj b/luxc/src/lux/analyser/env.clj
index 90fa39dfb..b8027a048 100644
--- a/luxc/src/lux/analyser/env.clj
+++ b/luxc/src/lux/analyser/env.clj
@@ -62,7 +62,7 @@
   (fn [state]
     (|case (&/get$ &/$scopes state)
       (&/$Nil)
-      ((&/fail-with-loc "[Analyser Error] Can't obtain captured vars without environments.")
+      ((&/fail-with-loc "[Analyser Error] Cannot obtain captured vars without environments.")
        state)
 
       (&/$Cons env _)
diff --git a/luxc/src/lux/analyser/lux.clj b/luxc/src/lux/analyser/lux.clj
index 1eecaf577..989ccb591 100644
--- a/luxc/src/lux/analyser/lux.clj
+++ b/luxc/src/lux/analyser/lux.clj
@@ -27,7 +27,7 @@
     _
     0))
 
-;; TODO: This technique won't work if the body of the type contains
+;; TODO: This technique will not work if the body of the type contains
 ;; nested quantifications that cannot be directly counted.
 (defn ^:private next-bound-type [type]
   "(-> Type Type)"
@@ -169,7 +169,7 @@
       (return x)
 
       _
-      (&/fail-with-loc "[Analyser Error] Can't expand to other than 1 element."))))
+      (&/fail-with-loc "[Analyser Error] Macro cannot expand to more than 1 output."))))
 
 (defn analyse-variant [analyse ?exo-type idx is-last? ?values]
   (|case ?exo-type
@@ -235,15 +235,15 @@
                 (&/map% (partial &&/clean-analysis $var) =exprs))))
           
           _
-          (&/fail-with-loc (str "[Analyser Error] Can't create variant if the expected type is " (&type/show-type exo-type*) " " idx " " (->> ?values (&/|map &/show-ast) (&/|interpose " ") (&/fold str "")))))
+          (&/fail-with-loc (str "[Analyser Error] Cannot create variant if the expected type is " (&type/show-type exo-type*) " " idx " " (->> ?values (&/|map &/show-ast) (&/|interpose " ") (&/fold str "")))))
         (fn [err]
           (|case exo-type
             (&/$VarT ?id)
             (|do [=exo-type (&type/deref ?id)]
-              (&/fail-with-loc (str err "\n" "[Analyser Error] Can't create variant if the expected type is " (&type/show-type =exo-type) " " idx " " (->> ?values (&/|map &/show-ast) (&/|interpose " ") (&/fold str "")))))
+              (&/fail-with-loc (str err "\n" "[Analyser Error] Cannot create variant if the expected type is " (&type/show-type =exo-type) " " idx " " (->> ?values (&/|map &/show-ast) (&/|interpose " ") (&/fold str "")))))
 
             _
-            (&/fail-with-loc (str err "\n" "[Analyser Error] Can't create variant if the expected type is " (&type/show-type exo-type) " " idx " " (->> ?values (&/|map &/show-ast) (&/|interpose " ") (&/fold str "")))))))
+            (&/fail-with-loc (str err "\n" "[Analyser Error] Cannot create variant if the expected type is " (&type/show-type exo-type) " " idx " " (->> ?values (&/|map &/show-ast) (&/|interpose " ") (&/fold str "")))))))
       )))
 
 (defn analyse-record [analyse exo-type ?elems]
@@ -293,7 +293,7 @@
                          state)
 
             _
-            ((&/fail-with-loc "[Analyser Error] Can't have anything other than a global def in the global environment.")
+            ((&/fail-with-loc "[Analyser Error] Cannot have anything other than a global def in the global environment.")
              state))
           ((&/fail-with-loc (str "[Analyser Error] Unknown global definition: " name))
            state))
@@ -363,9 +363,9 @@
             (return (&/T [=output-t (&/$Cons =arg =args)])))
 
           _
-          (&/fail-with-loc (str "[Analyser Error] Can't apply a non-function: " (&type/show-type ?fun-type*))))
+          (&/fail-with-loc (str "[Analyser Error] Cannot apply a non-function: " (&type/show-type ?fun-type*))))
         (fn [err]
-          (&/fail-with-loc (str err "\n" "[Analyser Error] Can't apply function " (&type/show-type fun-type) " to args: " (->> ?args (&/|map &/show-ast) (&/|interpose " ") (&/fold str "")))))))
+          (&/fail-with-loc (str err "\n" "[Analyser Error] Cannot apply function " (&type/show-type fun-type) " to args: " (->> ?args (&/|map &/show-ast) (&/|interpose " ") (&/fold str "")))))))
     ))
 
 (defn ^:private do-analyse-apply [analyse exo-type =fn ?args]
@@ -390,10 +390,11 @@
                                   ((&/fail-with-loc error) state)))
               ;; module-name &/get-module-name
               ;; :let [[r-prefix r-name] real-name
-              ;;       _ (->> (&/|map &/show-ast macro-expansion)
-              ;;              (&/|interpose "\n")
-              ;;              (&/fold str "")
-              ;;              (println 'macro-expansion (&/ident->text real-name) "@" module-name))]
+              ;;       _ (when (= "syntax:" r-name)
+              ;;           (->> (&/|map &/show-ast macro-expansion)
+              ;;                (&/|interpose "\n")
+              ;;                (&/fold str "")
+              ;;                (println 'macro-expansion (&/ident->text real-name) "@" module-name)))]
               ]
           (&/flat-map% (partial analyse exo-type) macro-expansion))
 
@@ -406,7 +407,7 @@
 
 (defn analyse-case [analyse exo-type ?value ?branches]
   (|do [:let [num-branches (&/|length ?branches)]
-        _ (&/assert! (> num-branches 0) "[Analyser Error] Can't have empty branches in \"case\" expression.")
+        _ (&/assert! (> num-branches 0) "[Analyser Error] Cannot have empty branches in \"case\" expression.")
         _ (&/assert! (even? num-branches) "[Analyser Error] Unbalanced branches in \"case\" expression.")
         =value (&&/analyse-1+ analyse ?value)
         :let [var?? (|case =value
@@ -548,25 +549,24 @@
 (defn analyse-def [analyse optimize eval! compile-def ?name ?value ?meta]
   (|do [_ &/ensure-statement
         module-name &/get-module-name
-        ? (&&module/defined? module-name ?name)]
-    (if ?
-      (&/fail-with-loc (str "[Analyser Error] Can't re-define " (str module-name ";" ?name)))
-      (|do [=value (&/without-repl-closure
-                    (&/with-scope ?name
-                      (&&/analyse-1+ analyse ?value)))
-            =meta (&&/analyse-1 analyse &type/Anns ?meta)
-            ==meta (eval! (optimize =meta))
-            _ (&&module/test-type module-name ?name ==meta (&&/expr-type* =value))
-            _ (&&module/test-macro module-name ?name ==meta (&&/expr-type* =value))
-            _ (compile-def ?name (optimize =value) ==meta)
-            ;; TODO: Make the call to &type/reset-mappings unnecessary.
-            ;; It shouldn't be necessary to reset the mappings of the
-            ;; type-vars, because those mappings shouldn't stay around
-            ;; after being cleaned-up.
-            ;; I must figure out why they're staying around.
-            _ &type/reset-mappings]
-        (return &/$Nil))
-      )))
+        ? (&&module/defined? module-name ?name)
+        _ (&/assert! (not ?)
+                     (&/fail-with-loc (str "[Analyser Error] Cannot re-define " (str module-name ";" ?name))))
+        =value (&/without-repl-closure
+                (&/with-scope ?name
+                  (&&/analyse-1+ analyse ?value)))
+        =meta (&&/analyse-1 analyse &type/Anns ?meta)
+        ==meta (eval! (optimize =meta))
+        _ (&&module/test-type module-name ?name ==meta (&&/expr-type* =value))
+        _ (&&module/test-macro module-name ?name ==meta (&&/expr-type* =value))
+        _ (compile-def ?name (optimize =value) ==meta)
+        ;; TODO: Make the call to &type/reset-mappings unnecessary.
+        ;; It should not be necessary to reset the mappings of the
+        ;; type-vars, because those mappings should not stay around
+        ;; after being cleaned-up.
+        ;; I must figure out why they're staying around.
+        _ &type/reset-mappings]
+    (return &/$Nil)))
 
 (defn ^:private merge-module-states
   "(-> Host Host Host)"
@@ -596,7 +596,7 @@
                            (&/get$ &&module/$defs)
                            &/|length
                            (= 0)))
-                ;; Don't modify the entry of the current module, to
+                ;; Do not modify the entry of the current module, to
                 ;; avoid overwritting it's data in improper ways.
                 ;; Since it's assumed the "original" old module
                 ;; contains all the proper own-module information.
@@ -635,13 +635,14 @@
                           (|let [[path alias] _import]
                             (&/without-repl
                              (&/save-module
-                              (|do [_ (if (= current-module path)
-                                        (&/fail-with-loc (str "[Analyser Error] Module can't import itself: " path))
-                                        (return nil))
+                              (|do [_ (&/assert! (not (= current-module path))
+                                                 (&/fail-with-loc (str "[Analyser Error] Module cannot import itself: " path)))
                                     already-compiled? (&&module/exists? path)
                                     active? (&&module/active-module? path)
+                                    ;; TODO: Enrich this error-message
+                                    ;; to explicitly show the cyclic dependency.
                                     _ (&/assert! (not active?)
-                                                 (str "[Analyser Error] Can't import a module that is mid-compilation: " path " @ " current-module))
+                                                 (str "[Analyser Error] Cannot import a module that is mid-compilation { cyclic dependency }: " path " @ " current-module))
                                     _ (&&module/add-import path)
                                     ?async (if (not already-compiled?)
                                              (compile-module path)
@@ -658,7 +659,7 @@
         ;; the environment forever, making type-checking slower.
         ;; The merging process for compilers more-or-less "fixes" the
         ;; problem by resetting the typing enviroment, but ideally
-        ;; those type-vars shouldn't survive in the first place.
+        ;; those type-vars should not survive in the first place.
         ;; TODO: MUST FIX
         _ (&/fold% (fn [compiler _async]
                      (|case @_async
diff --git a/luxc/src/lux/analyser/module.clj b/luxc/src/lux/analyser/module.clj
index 9df1054c8..0a7e336aa 100644
--- a/luxc/src/lux/analyser/module.clj
+++ b/luxc/src/lux/analyser/module.clj
@@ -81,7 +81,7 @@
   (|do [current-module &/get-module-name]
     (fn [state]
       (if (&/|member? module (->> state (&/get$ &/$modules) (&/|get current-module) (&/get$ $imports)))
-        ((&/fail-with-loc (str "[Analyser Error] Can't import module " (pr-str module) " twice @ " current-module))
+        ((&/fail-with-loc (str "[Analyser Error] Cannot import module " (pr-str module) " twice @ " current-module))
          state)
         (return* (&/update$ &/$modules
                             (fn [ms]
@@ -122,7 +122,7 @@
                nil)
       
       _
-      ((&/fail-with-loc (str "[Analyser Error] Can't create a new global definition outside of a global environment: " module ";" name))
+      ((&/fail-with-loc (str "[Analyser Error] Cannot create a new global definition outside of a global environment: " module ";" name))
        state))))
 
 (defn def-type
@@ -182,10 +182,10 @@
   (fn [state]
     (let [_module_ (->> state (&/get$ &/$modules) (&/|get module))]
       (if (&/|member? module (->> _module_ (&/get$ $imports)))
-        ((&/fail-with-loc (str "[Analyser Error] Can't create alias that is the same as a module nameL " (pr-str alias) " for " reference))
+        ((&/fail-with-loc (str "[Analyser Error] Cannot create alias that is the same as a module nameL " (pr-str alias) " for " reference))
          state)
         (if-let [real-name (->> _module_ (&/get$ $module-aliases) (&/|get alias))]
-          ((&/fail-with-loc (str "[Analyser Error] Can't re-use alias \"" alias "\" @ " module))
+          ((&/fail-with-loc (str "[Analyser Error] Cannot re-use alias \"" alias "\" @ " module))
            state)
           (return* (->> state
                         (&/update$ &/$modules
@@ -247,11 +247,11 @@
                   (return* state (&/T [(&/T [module name]) $def]))
 
                   _
-                  ((&/fail-with-loc (str "[Analyser Error @ find-def] Can't use unexported definition: " (str module &/+name-separator+ name)))
+                  ((&/fail-with-loc (str "[Analyser Error @ find-def] Cannot use unexported definition: " (str module &/+name-separator+ name)))
                    state))))
             ((&/fail-with-loc (str "[Analyser Error @ find-def] Definition does not exist: " (str module &/+name-separator+ name)))
              state))
-          ((&/fail-with-loc (str "[Analyser Error @ find-def] Module doesn't exist: " module))
+          ((&/fail-with-loc (str "[Analyser Error @ find-def] Module does not exist: " module))
            state))
         ((&/fail-with-loc (str "[Analyser Error @ find-def] Unknown module: " module))
          state))
@@ -311,7 +311,7 @@
   (|do [tags-table (tags-by-module module)
         _ (&/map% (fn [tag]
                     (if (&/|get tag tags-table)
-                      (&/fail-with-loc (str "[Analyser Error] Can't re-declare tag: " (&/ident->text (&/T [module tag]))))
+                      (&/fail-with-loc (str "[Analyser Error] Cannot re-declare tag: " (&/ident->text (&/T [module tag]))))
                       (return nil)))
                   tags)]
     (return nil)))
@@ -319,7 +319,7 @@
 (defn ensure-undeclared-type [module name]
   (|do [types-table (types-by-module module)
         _ (&/assert! (nil? (&/|get name types-table))
-                     (str "[Analyser Error] Can't re-declare type: " (&/ident->text (&/T [module name]))))]
+                     (str "[Analyser Error] Cannot re-declare type: " (&/ident->text (&/T [module name]))))]
     (return nil)))
 
 (defn declare-tags
@@ -329,7 +329,7 @@
         type-name (&type/type-name type)
         :let [[_module _name] type-name]
         _ (&/assert! (= module _module)
-                     (str "[Module Error] Can't define tags for a type belonging to a foreign module: " (&/ident->text type-name)))
+                     (str "[Module Error] Cannot define tags for a type belonging to a foreign module: " (&/ident->text type-name)))
         _ (ensure-undeclared-type _module _name)]
     (fn [state]
       (if-let [=module (->> state (&/get$ &/$modules) (&/|get module))]
@@ -361,7 +361,7 @@
             (if (or ?exported
                     (= module current-module))
               (return* state &/unit-tag)
-              ((&/fail-with-loc (str "[Analyser Error] Can't access tag #" (&/ident->text (&/T [module tag-name])) " from module " current-module))
+              ((&/fail-with-loc (str "[Analyser Error] Cannot access tag #" (&/ident->text (&/T [module tag-name])) " from module " current-module))
                state)))
           ((&/fail-with-loc (str "[Module Error] Unknown tag: " (&/ident->text (&/T [module tag-name]))))
            state))
@@ -408,7 +408,7 @@
     (|case (&meta/meta-get <tag> meta)
       (&/$Some (&/$BoolA true))
       (&/try-all% (&/|list (&type/check <type> type)
-                           (&/fail-with-loc (str "[Analyser Error] Can't tag as lux;" <desc> "? if it's not a " <desc> ": " (str module ";" name)))))
+                           (&/fail-with-loc (str "[Analyser Error] Cannot tag as lux;" <desc> "? if it's not a " <desc> ": " (str module ";" name)))))
 
       _
       (return nil)))
@@ -428,7 +428,7 @@
                 (return (&/T [_module _alias]))
 
                 _
-                (&/fail-with-loc "[Analyser Error] Wrong import syntax.")))
+                (&/fail-with-loc "[Analyser Error] Incorrect import syntax.")))
             _parts)
 
     _
diff --git a/luxc/src/lux/analyser/proc/js.clj b/luxc/src/lux/analyser/proc/js.clj
index 2d36dd0d9..ff6a21c11 100644
--- a/luxc/src/lux/analyser/proc/js.clj
+++ b/luxc/src/lux/analyser/proc/js.clj
@@ -89,5 +89,5 @@
     "null"         (analyse-js-null analyse exo-type ?values)
     "undefined"    (analyse-js-undefined analyse exo-type ?values)
     ;; else
-    (&/fail-with-loc (str "[Analyser Error] Unknown JS procedure: " proc)))
+    (&/fail-with-loc (str "[Analyser Error] Unknown host procedure: " ["js" proc])))
   )
diff --git a/luxc/src/lux/analyser/proc/jvm.clj b/luxc/src/lux/analyser/proc/jvm.clj
index 1d6075136..ec14aabb0 100644
--- a/luxc/src/lux/analyser/proc/jvm.clj
+++ b/luxc/src/lux/analyser/proc/jvm.clj
@@ -45,7 +45,7 @@
       (ensure-object type*))
 
     _
-    (&/fail-with-loc (str "[Analyser Error] Expecting object: " (&type/show-type type)))))
+    (&/fail-with-loc (str "[Analyser Error] Was expecting object type. Instead got: " (&type/show-type type)))))
 
 (defn ^:private as-object [type]
   "(-> Type Type)"
@@ -119,7 +119,9 @@
                                 gvars
                                 targs)]
         (&host-type/instance-param &type/existential gtype-env gtype))
-      (&/fail-with-loc (str "[Type Error] Mismatched number of type-parameters: " (&/|length gvars) " - " (&type/show-type obj-type))))
+      (&/fail-with-loc (str "[Type Error] Mismatched number of type-parameters for " (&type/show-type obj-type) "\n"
+                            "Expected: " (&/|length targs) "\n"
+                            "  Actual: " (&/|length gvars))))
 
     _
     (&/fail-with-loc (str "[Type Error] Type is not an object type: " (&type/show-type obj-type)))))
@@ -181,7 +183,7 @@
     (&/$GenericTypeVar var-name)
     (if-let [ex (&/|get var-name env)]
       (return ex)
-      (&/fail-with-loc (str "[Analysis Error] Unknown type var: " var-name)))
+      (&/fail-with-loc (str "[Analysis Error] Unknown type-var: " var-name)))
     
     (&/$GenericClass name params)
     (case name
@@ -987,7 +989,7 @@
       "b2l"          (analyse-jvm-b2l analyse exo-type ?values)
       "s2l"          (analyse-jvm-s2l analyse exo-type ?values)
       ;; else
-      (->> (&/fail-with-loc (str "[Analyser Error] Unknown JVM procedure: " proc))
+      (->> (&/fail-with-loc (str "[Analyser Error] Unknown host procedure: " ["jvm" proc]))
            (if-let [[_ _def-code] (re-find #"^interface:(.*)$" proc)]
              (|do [[_module _line _column] &/cursor]
                (&reader/with-source (str "interface@" "(" _module "," _line "," _column ")") _def-code
diff --git a/luxc/src/lux/base.clj b/luxc/src/lux/base.clj
index 582e2c96f..da6dcbf0a 100644
--- a/luxc/src/lux/base.clj
+++ b/luxc/src/lux/base.clj
@@ -722,7 +722,7 @@
       +init-bindings+]
      ))
 
-(do-template [<tag> <host> <ask> <change> <with>]
+(do-template [<tag> <host-desc> <host> <ask> <change> <with>]
   (do (def <host>
         (fn [compiler]
           (|case (get$ $host compiler)
@@ -730,7 +730,8 @@
             (return* compiler host-data)
 
             _
-            ((fail-with-loc "[Error] Wrong host.") compiler))))
+            ((fail-with-loc (str "[Error] Wrong host.\nExpected: " <host-desc>))
+             compiler))))
 
     (def <ask>
       (fn [compiler]
@@ -753,8 +754,8 @@
             new-val (<change> slot (fn [_] old-val))]
         (return ?output-val))))
 
-  $Jvm jvm-host jvm? change-jvm-host-slot with-jvm-host-slot
-  $Js  js-host  js?  change-js-host-slot  with-js-host-slot
+  $Jvm "JVM" jvm-host jvm? change-jvm-host-slot with-jvm-host-slot
+  $Js  "JS"  js-host  js?  change-js-host-slot  with-js-host-slot
   )
 
 (do-template [<name> <slot>]
@@ -774,7 +775,7 @@
       (return writer)
 
       _
-      (fail-with-loc "[Error] Writer hasn't been set."))))
+      (fail-with-loc "[Error] Writer has not been set."))))
 
 (defn with-writer [writer body]
   (with-jvm-host-slot $writer (fn [_] ($Some writer)) body))
@@ -879,7 +880,8 @@
     (try (let [top (|head (get$ $scopes state))]
            (return* state top))
       (catch Throwable _
-        ((fail-with-loc "[Error] No local environment.") state)))))
+        ((fail-with-loc "[Error] No local environment.")
+         state)))))
 
 (def gen-id
   (fn [state]
@@ -908,7 +910,8 @@
   (fn [state]
     (|case (|reverse (get$ $scopes state))
       ($Nil)
-      ((fail-with-loc "[Analyser Error] Can't get the module-name without a module.") state)
+      ((fail-with-loc "[Analyser Error] Cannot get the module-name without a module.")
+       state)
 
       ($Cons ?global _)
       (return* state (|head (get$ $name ?global))))))
@@ -918,7 +921,8 @@
   (fn [state]
     (if-let [module (|get name (get$ $modules state))]
       (return* state module)
-      ((fail-with-loc (str "[Error] Unknown module: " name)) state))))
+      ((fail-with-loc (str "[Error] Unknown module: " name))
+       state))))
 
 (def get-current-module
   "(Lux (Module Compiler))"
@@ -1061,7 +1065,8 @@
       (return* state unit-tag)
 
       ($Some _)
-      ((fail-with-loc "[Error] All statements must be top-level forms.") state))))
+      ((fail-with-loc "[Error] All statements must be top-level forms.")
+       state))))
 
 (def cursor
   ;; (Lux Cursor)
@@ -1250,7 +1255,7 @@
     (return init)
 
     [_ _]
-    (assert false "Lists don't match in size.")))
+    (assert false "Lists do not match in size.")))
 
 (defn map2% [f xs ys]
   (|case [xs ys]
@@ -1263,7 +1268,7 @@
     (return $Nil)
 
     [_ _]
-    (assert false "Lists don't match in size.")))
+    (assert false "Lists do not match in size.")))
 
 (defn map2 [f xs ys]
   (|case [xs ys]
diff --git a/luxc/src/lux/compiler/cache/ann.clj b/luxc/src/lux/compiler/cache/ann.clj
index 5256fa0af..b71d6707b 100644
--- a/luxc/src/lux/compiler/cache/ann.clj
+++ b/luxc/src/lux/compiler/cache/ann.clj
@@ -148,7 +148,7 @@
       (deserialize-ident input)
       (deserialize-list input)
       (deserialize-dict input)
-      (assert false "[Cache error] Can't deserialize annocation.")))
+      (assert false "[Cache error] Cannot deserialize annocation.")))
 
 (defn deserialize-anns
   "(-> Text Text)"
diff --git a/luxc/src/lux/compiler/cache/type.clj b/luxc/src/lux/compiler/cache/type.clj
index 6bddef9c1..26a08e193 100644
--- a/luxc/src/lux/compiler/cache/type.clj
+++ b/luxc/src/lux/compiler/cache/type.clj
@@ -156,4 +156,4 @@
       (deserialize-univq input)
       (deserialize-exq input)
       (deserialize-host input)
-      (assert false (str "[Cache error] Can't deserialize type. --- " input))))
+      (assert false (str "[Cache error] Cannot deserialize type. --- " input))))
diff --git a/luxc/src/lux/compiler/core.clj b/luxc/src/lux/compiler/core.clj
index 15f03ea6e..a43a6ff48 100644
--- a/luxc/src/lux/compiler/core.clj
+++ b/luxc/src/lux/compiler/core.clj
@@ -22,7 +22,7 @@
 
 ;; [Utils]
 (defn write-file [^String file-name ^bytes data]
-  (do (assert (not (.exists (File. file-name))) (str "Can't overwrite file: " file-name))
+  (do (assert (not (.exists (File. file-name))) (str "Cannot overwrite file: " file-name))
     (with-open [stream (BufferedOutputStream. (FileOutputStream. file-name))]
       (.write stream data)
       (.flush stream))))
diff --git a/luxc/src/lux/compiler/io.clj b/luxc/src/lux/compiler/io.clj
index f129fd3f0..46a3fdfd7 100644
--- a/luxc/src/lux/compiler/io.clj
+++ b/luxc/src/lux/compiler/io.clj
@@ -37,4 +37,4 @@
         (return (&/T [host-file-name code]))
         (if-let [code (get @!libs lux-file-name)]
           (return (&/T [lux-file-name code]))
-          (&/fail-with-loc (str "[I/O Error] Module doesn't exist: " module-name)))))))
+          (&/fail-with-loc (str "[I/O Error] Module does not exist: " module-name)))))))
diff --git a/luxc/src/lux/compiler/js.clj b/luxc/src/lux/compiler/js.clj
index be405ad33..68d4e0997 100644
--- a/luxc/src/lux/compiler/js.clj
+++ b/luxc/src/lux/compiler/js.clj
@@ -139,7 +139,7 @@
                 (let [compiler-step (&analyser/analyse &optimizer/optimize eval! compile-module!! all-compilers)]
                   (|do [module-exists? (&a-module/exists? name)]
                     (if module-exists?
-                      (&/fail-with-loc (str "[Compiler Error] Can't re-define a module: " name))
+                      (&/fail-with-loc (str "[Compiler Error] Cannot re-define a module: " name))
                       (|do [_ (&&cache/delete name)
                             _ (&&/init-buffer)
                             _ (&a-module/create-module name file-hash)
diff --git a/luxc/src/lux/compiler/js/lux.clj b/luxc/src/lux/compiler/js/lux.clj
index bf188803c..d066dff17 100644
--- a/luxc/src/lux/compiler/js/lux.clj
+++ b/luxc/src/lux/compiler/js/lux.clj
@@ -97,7 +97,7 @@
 
 (defn compile-iter [compile register-offset ?args]
   ;; Can only optimize if it is a simple expression.
-  ;; Won't work if it's inside an 'if', unlike on the JVM.
+  ;; Will not work if it's inside an 'if', unlike on the JVM.
   ;; (|do [[updates _] (&/fold% (fn [updates+offset ?arg]
   ;;                              (|let [[updates offset] updates+offset
   ;;                                     already-set? (|case ?arg
@@ -368,7 +368,7 @@
                   (return nil))
 
                 [false (&/$Some _)]
-                (&/fail-with-loc "[Compiler Error] Can't define tags for non-type.")
+                (&/fail-with-loc "[Compiler Error] Cannot define tags for non-type.")
 
                 [true (&/$Some _)]
                 (&/fail-with-loc "[Compiler Error] Incorrect format for tags.")
diff --git a/luxc/src/lux/compiler/js/proc/common.clj b/luxc/src/lux/compiler/js/proc/common.clj
index 4fdff5f21..eb4e27857 100644
--- a/luxc/src/lux/compiler/js/proc/common.clj
+++ b/luxc/src/lux/compiler/js/proc/common.clj
@@ -604,4 +604,4 @@
       )
     
     ;; else
-    (&/fail-with-loc (str "[Compiler Error] Unknown host procedure: " [category proc]))))
+    (&/fail-with-loc (str "[Compiler Error] Unknown procedure: " [category proc]))))
diff --git a/luxc/src/lux/compiler/jvm.clj b/luxc/src/lux/compiler/jvm.clj
index 6c4731e16..150ec54f4 100644
--- a/luxc/src/lux/compiler/jvm.clj
+++ b/luxc/src/lux/compiler/jvm.clj
@@ -180,7 +180,7 @@
                   (let [compiler-step (&analyser/analyse &optimizer/optimize eval! compile-module!! all-compilers)]
                     (|do [module-exists? (&a-module/exists? name)]
                       (if module-exists?
-                        (&/fail-with-loc "[Compiler Error] Can't re-define a module!")
+                        (&/fail-with-loc (str "[Compiler Error] Cannot re-define a module: " name))
                         (|do [_ (&&cache/delete name)
                               _ (&a-module/create-module name file-hash)
                               _ (&a-module/flag-active-module name)
diff --git a/luxc/src/lux/compiler/jvm/lux.clj b/luxc/src/lux/compiler/jvm/lux.clj
index 12a2f83c7..e14615946 100644
--- a/luxc/src/lux/compiler/jvm/lux.clj
+++ b/luxc/src/lux/compiler/jvm/lux.clj
@@ -310,7 +310,9 @@
                         def-meta ?meta]
                   def-value (try (return (-> def-class (.getField &/value-field) (.get nil)))
                               (catch Throwable t
-                                (&/assert! "Error during value initialization." (throwable->text t))))
+                                (&/assert! false
+                                           (str "Error during value initialization:\n"
+                                                (throwable->text t)))))
                   _ (&/without-repl-closure
                      (&a-module/define module-name ?name def-type def-meta def-value))
                   _ (|case (&/T [is-type? (&a-meta/meta-get &a-meta/tags-tag def-meta)])
@@ -333,7 +335,7 @@
                         (return nil))
 
                       [false (&/$Some _)]
-                      (&/fail-with-loc "[Compiler Error] Can't define tags for non-type.")
+                      (&/fail-with-loc "[Compiler Error] Cannot define tags for non-type.")
 
                       [true (&/$Some _)]
                       (&/fail-with-loc "[Compiler Error] Incorrect format for tags.")
@@ -377,7 +379,9 @@
                       def-meta ?meta]
                 def-value (try (return (-> def-class (.getField &/value-field) (.get nil)))
                             (catch Throwable t
-                              (&/assert! "Error during value initialization." (throwable->text t))))
+                              (&/assert! false
+                                         (str "Error during value initialization:\n"
+                                              (throwable->text t)))))
                 _ (&/without-repl-closure
                    (&a-module/define module-name ?name def-type def-meta def-value))
                 _ (|case (&/T [is-type? (&a-meta/meta-get &a-meta/tags-tag def-meta)])
@@ -400,7 +404,7 @@
                       (return nil))
 
                     [false (&/$Some _)]
-                    (&/fail-with-loc "[Compiler Error] Can't define tags for non-type.")
+                    (&/fail-with-loc "[Compiler Error] Cannot define tags for non-type.")
 
                     [true (&/$Some _)]
                     (&/fail-with-loc "[Compiler Error] Incorrect format for tags.")
diff --git a/luxc/src/lux/compiler/jvm/rt.clj b/luxc/src/lux/compiler/jvm/rt.clj
index 9bc94427e..5d3a1ad09 100644
--- a/luxc/src/lux/compiler/jvm/rt.clj
+++ b/luxc/src/lux/compiler/jvm/rt.clj
@@ -254,7 +254,7 @@
          ;; done to ensure variants were never created with null
          ;; values (this would interfere later with
          ;; pattern-matching).
-         ;; Since Lux itself doesn't have null values as part of
+         ;; Since Lux itself does not have null values as part of
          ;; the language, the burden of ensuring non-nulls was
          ;; shifted to library code dealing with host-interop, to
          ;; ensure variant-making was as fast as possible.
@@ -285,7 +285,7 @@
                ;; (.visitLabel $is-null)
                ;; (.visitTypeInsn Opcodes/NEW "java/lang/IllegalStateException")
                ;; (.visitInsn Opcodes/DUP)
-               ;; (.visitLdcInsn "Can't create variant for null pointer")
+               ;; (.visitLdcInsn "Cannot create variant for null pointer")
                ;; (.visitMethodInsn Opcodes/INVOKESPECIAL "java/lang/IllegalStateException" "<init>" "(Ljava/lang/String;)V")
                ;; (.visitInsn Opcodes/ATHROW)
                (.visitMaxs 0 0)
diff --git a/luxc/src/lux/host/generics.clj b/luxc/src/lux/host/generics.clj
index 5dd95bb9b..9e0359760 100644
--- a/luxc/src/lux/host/generics.clj
+++ b/luxc/src/lux/host/generics.clj
@@ -172,7 +172,7 @@
         (->bytecode-class-name name))
 
       (&/$GenericArray param)
-      (assert false "gclass->bytecode-class-name* doesn't work on arrays."))))
+      (assert false "gclass->bytecode-class-name* does not work on arrays."))))
 
 (let [object-bc-name (->bytecode-class-name "java.lang.Object")]
   (defn gclass->bytecode-class-name [gclass]
@@ -188,7 +188,7 @@
       (->bytecode-class-name name)
 
       (&/$GenericArray param)
-      (assert false "gclass->bytecode-class-name doesn't work on arrays."))))
+      (assert false "gclass->bytecode-class-name does not work on arrays."))))
 
 (defn method-signatures [method-decl]
   (|let [[=name =anns =gvars =exceptions =inputs =output] method-decl
diff --git a/luxc/src/lux/lexer.clj b/luxc/src/lux/lexer.clj
index 2f9c0717e..58f8f95f7 100644
--- a/luxc/src/lux/lexer.clj
+++ b/luxc/src/lux/lexer.clj
@@ -101,7 +101,7 @@
                               (return pre-quotes**))
         [pre-quotes post-quotes] (if (.endsWith pre-quotes* "\\")
                                    (if eol?
-                                     (&/fail-with-loc "[Lexer Error] Can't leave dangling back-slash \\")
+                                     (&/fail-with-loc "[Lexer Error] Cannot leave dangling back-slash \\")
                                      (if (if-let [^String back-slashes (re-find #"\\+$" pre-quotes*)]
                                            (odd? (.length back-slashes)))
                                        (|do [[_ eol?* _] (&reader/read-regex #"^([\"])")
diff --git a/luxc/src/lux/optimizer.clj b/luxc/src/lux/optimizer.clj
index a3ce2c089..9fc50646e 100644
--- a/luxc/src/lux/optimizer.clj
+++ b/luxc/src/lux/optimizer.clj
@@ -25,7 +25,7 @@
 
   ;; These other tags represent higher-order constructs that manifest
   ;; themselves as patterns in the code.
-  ;; Lux doesn't formally provide these features, but some macros
+  ;; Lux does not formally provide these features, but some macros
   ;; expose ways to implement them in terms of the other (primitive)
   ;; features.
   ;; The optimizer looks for those usage patterns and transforms them
@@ -59,7 +59,7 @@
 ;; (possibly) branching path, where each step along the path
 ;; corresponds to a value, the ends of the path are the jumping-off
 ;; points for the bodies of branches, and branching decisions can be
-;; backtracked, if they don't result in a valid jump.
+;; backtracked, if they do not result in a valid jump.
 (defvariant
   ;; Throw away the current data-node (CDN). It's useless.
   ("PopPM" 0)
@@ -213,7 +213,7 @@
 
     (&a-case/$TupleTestAC _sub-tests)
     (|case _sub-tests
-      ;; An empty tuple corresponds to unit, which can't be tested in
+      ;; An empty tuple corresponds to unit, which cannot be tested in
       ;; any meaningful way, so it's just popped.
       (&/$Nil)
       (&/|list $PopPM)
@@ -844,7 +844,7 @@
 
 ;; [[Loop Optimizations]]
 
-;; Lux doesn't offer any looping constructs, relying instead on
+;; Lux does not offer any looping constructs, relying instead on
 ;; recursion.
 ;; Some common usages of recursion can be written more efficiently
 ;; just using regular loops/iteration.
diff --git a/luxc/src/lux/parser.clj b/luxc/src/lux/parser.clj
index 3323dadfc..3f0a95653 100644
--- a/luxc/src/lux/parser.clj
+++ b/luxc/src/lux/parser.clj
@@ -45,9 +45,9 @@
         :let [elems (&/fold &/|++ &/$Nil elems*)]]
     (|case token
       [meta (&lexer/$Close_Brace _)]
-      (if (even? (&/|length elems))
-        (return (&/$RecordS (&/|as-pairs elems)))
-        (&/fail-with-loc base-uneven-record-error))
+      (|do [_ (&/assert! (even? (&/|length elems))
+                         (&/fail-with-loc base-uneven-record-error))]
+        (return (&/$RecordS (&/|as-pairs elems))))
       
       _
       (&/fail-with-loc "[Parser Error] Unbalanced braces.")
diff --git a/luxc/src/lux/type.clj b/luxc/src/lux/type.clj
index dd2e536bb..47b4b9c38 100644
--- a/luxc/src/lux/type.clj
+++ b/luxc/src/lux/type.clj
@@ -178,7 +178,7 @@
         
         (&/$None)
         (return* state false))
-      ((&/fail-with-loc (str "[Type Error] <bound?> Unknown type-var: " id))
+      ((&/fail-with-loc (str "[Type Error] Unknown type-var: " id))
        state))))
 
 (defn deref [id]
@@ -191,7 +191,7 @@
         (&/$None)
         ((&/fail-with-loc (str "[Type Error] Unbound type-var: " id))
          state))
-      ((&/fail-with-loc (str "[Type Error] <deref> Unknown type-var: " id))
+      ((&/fail-with-loc (str "[Type Error] Unknown type-var: " id))
        state))))
 
 (defn deref+ [type]
@@ -210,7 +210,7 @@
         (&/$Some bound)
         (if (type= type bound)
           (return* state nil)
-          ((&/fail-with-loc (str "[Type Error] Can't re-bind type var: " id " | Current type: " (show-type bound)))
+          ((&/fail-with-loc (str "[Type Error] Cannot re-bind type var: " id " | Current type: " (show-type bound)))
            state))
         
         (&/$None)
@@ -218,7 +218,7 @@
                                                             ts))
                             state)
                  nil))
-      ((&/fail-with-loc (str "[Type Error] <set-var> Unknown type-var: " id " | " (->> state (&/get$ &/$type-vars) (&/get$ &/$mappings) &/|length)))
+      ((&/fail-with-loc (str "[Type Error] Unknown type-var: " id " | " (->> state (&/get$ &/$type-vars) (&/get$ &/$mappings) &/|length)))
        state))))
 
 (defn reset-var [id type]
@@ -228,7 +228,7 @@
                                                           ts))
                           state)
                nil)
-      ((&/fail-with-loc (str "[Type Error] <set-var> Unknown type-var: " id " | " (->> state (&/get$ &/$type-vars) (&/get$ &/$mappings) &/|length)))
+      ((&/fail-with-loc (str "[Type Error] Unknown type-var: " id " | " (->> state (&/get$ &/$type-vars) (&/get$ &/$mappings) &/|length)))
        state))))
 
 (defn unset-var [id]
@@ -238,7 +238,7 @@
                                                           ts))
                           state)
                nil)
-      ((&/fail-with-loc (str "[Type Error] <set-var> Unknown type-var: " id " | " (->> state (&/get$ &/$type-vars) (&/get$ &/$mappings) &/|length)))
+      ((&/fail-with-loc (str "[Type Error] Unknown type-var: " id " | " (->> state (&/get$ &/$type-vars) (&/get$ &/$mappings) &/|length)))
        state))))
 
 ;; [Exports]
@@ -422,7 +422,7 @@
         _
         (&/fail-with-loc (str "[Type Error] Type is not a " <desc> ": " (show-type type))))))
 
-  &/$SumT  flatten-sum  sum-at "Sum"
+  &/$SumT  flatten-sum  sum-at  "Sum"
   &/$ProdT flatten-prod prod-at "Product"
   )
 
@@ -583,9 +583,9 @@
   (|do [=expected (show-type+ expected)
         =actual (show-type+ actual)]
     (&/fail-with-loc (str (if (= "" err) err (str err "\n"))
-                          "[Type Checker]\n"
+                          "[Type Checker Error]\n"
                           "Expected: " =expected "\n\n"
-                          "Actual:   " =actual
+                          "  Actual: " =actual
                           "\n"))))
 
 (defn beta-reduce [env type]
diff --git a/luxc/src/lux/type/host.clj b/luxc/src/lux/type/host.clj
index 40a3373f0..e2f7c1c1f 100644
--- a/luxc/src/lux/type/host.clj
+++ b/luxc/src/lux/type/host.clj
@@ -114,9 +114,10 @@
         (let [gvar (.getName ^TypeVariable refl-type)]
           (if-let [m-type (&/|get gvar matchings)]
             (return m-type)
-            (&/fail-with-loc (str "[Type Error] Unknown generic type variable: " gvar " -- " (->> matchings
-                                                                                       (&/|map &/|first)
-                                                                                       &/->seq)))))
+            (&/fail-with-loc (str "[Host Error] Unknown generic type-variable: " gvar "\n"
+                                  "Available type-variables: " (->> matchings
+                                                                    (&/|map &/|first)
+                                                                    &/->seq)))))
         
         (instance? WildcardType refl-type)
         (if-let [bound (->> ^WildcardType refl-type .getUpperBounds seq first)]
@@ -175,9 +176,10 @@
     (&/$GenericTypeVar var-name)
     (if-let [m-type (&/|get var-name matchings)]
       (return m-type)
-      (&/fail-with-loc (str "[Type Error] Unknown generic type variable: " var-name " -- " (->> matchings
-                                                                                     (&/|map &/|first)
-                                                                                     &/->seq))))
+      (&/fail-with-loc (str "[Host Error] Unknown generic type-variable: " var-name "\n"
+                            "Available type-variables: " (->> matchings
+                                                              (&/|map &/|first)
+                                                              &/->seq))))
     
     (&/$GenericWildcard)
     existential))
@@ -231,7 +233,7 @@
       (let [lineage (trace-lineage sub-class+ super-class+)]
         (|do [[^Class sub-class* sub-params*] (raise existential lineage sub-class+ sub-params)]
           (return (&/$HostT (.getName sub-class*) sub-params*))))
-      (&/fail-with-loc (str "[Type Error] Classes don't have a subtyping relationship: " sub-class " </= " super-class)))))
+      (&/fail-with-loc (str "[Host Error] Classes do not have a subtyping relationship: " sub-class " </= " super-class)))))
 
 (defn as-obj [class]
   (case class