Correctly handle EOF when the last entity is a function with a single-expression body that ends in an unnamed function

Before this, we emitted an "unexpected end of source file" in the specific case that the very last entity in a source file was a function with a single-expression body that ended in an unnamed function that also had a single-expression body that ended in an unnamed function -- I specifically don't require two `;` there, and making the second `;` optional exposes expression parsing to EOF. Solution: Check `done()` in the places that could be the end of an expression-statement, in case we consumed all the tokens already in this particular edge case.

Author: hsutter

source/parse.h

@@ -1635,7 +1635,7 @@ class parser
             return {};
         }
 
-        while (
+        while ( !done() && (
             (is_postfix_operator(curr().type())
                 //  Postfix operators must be lexically adjacent
                 && curr().position().lineno == peek(-1)->position().lineno
@@ -1645,6 +1645,7 @@ class parser
             curr().type() == lexeme::LeftParen ||
             curr().type() == lexeme::Dot
             )
+            )
         {
             //  these can't be unary operators if followed by a (, identifier, or literal
             if ((curr().type() == lexeme::Multiply  || curr().type() == lexeme::Ampersand || curr().type() == lexeme::Tilde) &&
@@ -1773,7 +1774,7 @@ class parser
         auto n = std::make_unique<Binary>();
         if ( (n->expr = term()) )
         {
-            while (true)
+            while (!done())
             {
                 typename Binary::term t{};
 
@@ -2171,7 +2172,7 @@ class parser
         auto is_found = false;
         auto as_found = false;
 
-        while (curr() == "is" || curr() == "as")
+        while (!done() && (curr() == "is" || curr() == "as"))
         {
             if (curr() == "is") {
                 if (is_found) {
@@ -2412,7 +2413,7 @@ class parser
             return {};
         }
 
-        if (semicolon_required && curr().type() != lexeme::Semicolon &&
+        if (semicolon_required && (done() || curr().type() != lexeme::Semicolon) &&
             peek(-1)->type() != lexeme::Semicolon
                 //  this last peek(-1)-condition is a hack (? or is it just
                 //  maybe elegant? I'm torn) so that code like
@@ -2426,7 +2427,7 @@ class parser
         {
             return {};
         }
-        if (curr().type() == lexeme::Semicolon) {
+        if (!done() && curr().type() == lexeme::Semicolon) {
             n->has_semicolon = true;
             next();
         }