Simple check for [in] and [out] parameters.

test/test_suite/errors/try_with_chained_unwrap_errors.c3

@@ -9,7 +9,7 @@ fn void test2()
     int! a;
     int b;
     if (try b = a) {}
-    if (try test2 = a) {} // #error: 'try' expected an assignable variable or expression here, did you make a mistake?
+    if (try test2 = a) {} // #error: An assignable expression
 }
 
 const int BAZ = 1;
@@ -19,7 +19,7 @@ fn void test3()
 
     int! a;
     int b;
-    if (try BAZ = a) {} // #error: 'try' expected an assignable variable or expression here, did you make a mistake?
+    if (try BAZ = a) {} // #error: An assignable expression
 }
 
 

test/test_suite/expressions/arithmetics_sema_fail.c3

@@ -17,32 +17,32 @@ fn void test9()
 
 fn void test10()
 {
-    10 = 20;        // #error: This expression is not assignable
+    10 = 20;        // #error: An assignable expression
 }
 
 fn void test11()
 {
-    '10' = '20';        // #error: This expression is not assignable
+    '10' = '20';        // #error: An assignable expression
 }
 
 fn void test12()
 {
-    true = false;        // #error: This expression is not assignable
+    true = false;        // #error: An assignable expression
 }
 
 fn void test13()
 {
-    "a" = "b";        // #error: This expression is not assignable
+    "a" = "b";        // #error: An assignable expression
 }
 
 fn void test14()
 {
-    1.2 = 1.3;        // #error: This expression is not assignable
+    1.2 = 1.3;        // #error: An assignable expression
 }
 
 fn void test15()
 {
-    null = null;      // #error: This expression is not assignable
+    null = null;      // #error: An assignable expression
 }
 
 fn void test16()

test/test_suite/expressions/assignability.c3

@@ -2,34 +2,34 @@ define Number = int;
 
 fn void test1()
 {
-    10 = 20;        // #error: This expression is not assignable
+    10 = 20;        // #error: An assignable expression
 }
 
 fn void test2()
 {
-    "foo" = "bar";  // #error: This expression is not assignable
+    "foo" = "bar";  // #error: An assignable expression
 }
 
 fn void test3()
 {
-    true = false;   // #error: This expression is not assignable
+    true = false;   // #error: An assignable expression
 }
 
 fn void test4()
 {
-    'c' = 'd';      // #error: This expression is not assignable
+    'c' = 'd';      // #error: An assignable expression
 }
 
 fn void test5()
 {
-    3.14 = 2.14;    // #error: This expression is not assignable
+    3.14 = 2.14;    // #error: An assignable expression
 }
 
 fn void test21()
 {
     int a = 0;
     int b = 2;
-    a++ = b++;      // #error: This expression is not assignable
+    a++ = b++;      // #error: An assignable expression
 }
 
 fn void test22()

test/test_suite/symbols/various.c3

@@ -62,7 +62,7 @@ fn void test9()
 {
     const char A = 1;
     char b = A;
-    A = b;              // #error: This expression is not assignable, did you make
+    A = b;              // #error: An assignable expression
 }
 
 fn void test10()