Fix more fuzz crashes.

Author: threeifbyair

regression-tests/mixed-bugfix-for-double-poundelse.cpp2

@@ -0,0 +1,2 @@
+#else
+#else

regression-tests/pure2-bugfix-for-bad-parameter.cpp2

@@ -0,0 +1 @@
+print: <T: type> (inout out: std::ostream=args: T) requires true = {}

regression-tests/pure2-bugfix-for-naked-unsigned-char.cpp2

@@ -0,0 +1,3 @@
+main: () = {
+    e: unsigned char
+}

regression-tests/test-results/mixed-bugfix-for-double-poundelse.cpp2.output

@@ -0,0 +1,5 @@
+mixed-bugfix-for-double-poundelse.cpp2...
+mixed-bugfix-for-double-poundelse.cpp2(2,1): error: #else does not match a prior #if
+mixed-bugfix-for-double-poundelse.cpp2(3,1): error: #else does not match a prior #if
+mixed-bugfix-for-double-poundelse.cpp2(3,1): error: #else already encountered for this #if
+

regression-tests/test-results/pure2-bugfix-for-bad-parameter.cpp2.output

@@ -0,0 +1,3 @@
+pure2-bugfix-for-bad-parameter.cpp2...
+pure2-bugfix-for-bad-parameter.cpp2(1,50): error: parameter must be initialized with an expression (at ')')
+

regression-tests/test-results/pure2-bugfix-for-naked-unsigned-char.cpp2.output

@@ -0,0 +1,8 @@
+pure2-bugfix-for-naked-unsigned-char.cpp2...
+pure2-bugfix-for-naked-unsigned-char.cpp2(2,8): error: 'unsigned char' - did you mean 'u8' (usually best) or 'cpp2::_uchar'?
+pure2-bugfix-for-naked-unsigned-char.cpp2(2,8): error: 'unsigned char' is an old-style C/C++ multi-word keyword type
+    - most such types should be used only for interoperability with older code
+    - using those when you need them is fine, but name them with these short names instead:
+        short, ushort, int, uint, long, ulong, longlong, ulonglong, longdouble, _schar, _uchar
+    - see also cpp2util.h > "Convenience names for integer types"
+

source/io.h

@@ -362,9 +362,11 @@ class braces_tracker
             else             { --else_net_braces; }
         }
 
-        auto found_preprocessor_else() -> void {
-            assert (!found_else);
+        auto found_preprocessor_else_was_there_another() -> bool {
+            if (found_else)
+                return true; 
             found_else = true;
+            return false;
         }
 
         //  If the "if" and "else" branches opened/closed the same net number
@@ -469,7 +471,14 @@ class braces_tracker
             );
         }
 
-        preprocessor.back().found_preprocessor_else();
+        if (preprocessor.back().found_preprocessor_else_was_there_another()) {
+            //  If this is the second or subsequent #else, it doesn't match
+            //  the prior #if, so report an error
+            errors.emplace_back(
+                lineno,
+                "#else already encountered for this #if"
+            );
+        };
     }
 
     //  Exiting an #endif

source/lex.h

@@ -713,13 +713,18 @@ auto lex_line(
             tokens.pop_back();
             ++num_merged_tokens;
         }
-
-        tokens.push_back({
-            &generated_text.back()[0],
-            std::ssize(generated_text.back()),
-            pos,
-            lexeme::Keyword
-            });
+ 
+        // It's an error to have more than one of these, but we require that
+        // the number of tokens has not gone down. So just push back as many
+        // tokens as we merged. This will ensure that the token count remains
+        // the same. 
+        for (auto i = 0; i < num_merged_tokens; i++)
+            tokens.push_back({
+                &generated_text.back()[0],
+                std::ssize(generated_text.back()),
+                pos,
+                lexeme::Keyword
+                });
 
         if (num_merged_tokens > 1)
         {
@@ -750,8 +755,6 @@ auto lex_line(
                 "        short, ushort, int, uint, long, ulong, longlong, ulonglong, longdouble, _schar, _uchar\n"
                 "    - see also cpp2util.h > \"Convenience names for integer types\""
             );
-
-            return;
         }
 
         tokens.push_back(last_token);

source/parse.h

@@ -8684,6 +8684,18 @@ class parser
             }
         }
 
+        if (
+            !is_returns
+            && n->declaration->initializer
+            && !n->declaration->initializer->is_expression()
+            )
+        {
+            //  If the initializer is not an expression statement (like a function call),
+            //  then it can't be used as a parameter.
+            error("parameter must be initialized with an expression");
+            return {};
+        }
+
         return n;
     }