fix(parse): recognize parameter named after contextual keyword

regression-tests/pure2-bugfix-for-parameter-named-after-contextual-keyword-error.cpp2

@@ -0,0 +1 @@
+f: (virtual) = { }

regression-tests/pure2-bugfix-for-parameter-named-after-contextual-keyword.cpp2

@@ -0,0 +1,10 @@
+t: type = {
+  f: (in) -> _ = in;
+}
+g: (final) -> _ = final.first;
+h: (out, x) -> _ = out(x);
+main: () = {
+  [[assert: t::f(0) == 0]]
+  [[assert: g(std::make_pair(1, 2)) == 1]]
+  [[assert: h(:(y) -> _ = y, 3) == 3]]
+}

regression-tests/test-results/pure2-bugfix-for-parameter-named-after-contextual-keyword-error.cpp2.output

@@ -0,0 +1,3 @@
+pure2-bugfix-for-parameter-named-after-contextual-keyword-error.cpp2...
+pure2-bugfix-for-parameter-named-after-contextual-keyword-error.cpp2(1,5): error: invalid parameter identifier (at 'virtual')
+

regression-tests/test-results/pure2-bugfix-for-parameter-named-after-contextual-keyword.cpp

@@ -0,0 +1,42 @@
+
+#define CPP2_USE_MODULES         Yes
+
+//=== Cpp2 type declarations ====================================================
+
+
+#include "cpp2util.h"
+
+#line 1 "pure2-bugfix-for-parameter-named-after-contextual-keyword.cpp2"
+class t;
+
+
+//=== Cpp2 type definitions and function declarations ===========================
+
+#line 1 "pure2-bugfix-for-parameter-named-after-contextual-keyword.cpp2"
+class t {
+  public: [[nodiscard]] static auto f(auto const& in) -> auto;
+
+  public: t() = default;
+  public: t(t const&) = delete; /* No 'that' constructor, suppress copy */
+  public: auto operator=(t const&) -> void = delete;
+#line 3 "pure2-bugfix-for-parameter-named-after-contextual-keyword.cpp2"
+};
+[[nodiscard]] auto g(auto const& final) -> auto;
+[[nodiscard]] auto h(auto const& out, auto const& x) -> auto;
+auto main() -> int;
+
+
+//=== Cpp2 function definitions =================================================
+
+
+#line 2 "pure2-bugfix-for-parameter-named-after-contextual-keyword.cpp2"
+  [[nodiscard]] auto t::f(auto const& in) -> auto { return in;  }
+
+[[nodiscard]] auto g(auto const& final) -> auto { return final.first;  }
+[[nodiscard]] auto h(auto const& out, auto const& x) -> auto { return out(x);  }
+auto main() -> int{
+  cpp2::Default.expects(t::f(0)==0, "");
+  cpp2::Default.expects(g(std::make_pair(1, 2))==1, "");
+  cpp2::Default.expects(h([](auto const& y) -> auto { return y;  }, 3)==3, "");
+}
+

regression-tests/test-results/pure2-bugfix-for-parameter-named-after-contextual-keyword.cpp2.output

@@ -0,0 +1,2 @@
+pure2-bugfix-for-parameter-named-after-contextual-keyword.cpp2... ok (all Cpp2, passes safety checks)
+

source/parse.h

@@ -5787,6 +5787,7 @@ class parser
 
         //  Handle optional this-specifier
         //
+        auto this_specifier_pos = pos; // For backtracking if it's to be an identifier.
         if (curr() == "implicit") {
             n->mod = parameter_declaration_node::modifier::implicit;
             next();
@@ -5806,6 +5807,7 @@ class parser
 
         //  Handle optional parameter-direction
         //
+        auto parameter_direction_pos = pos; // For backtracking if it's to be an identifier.
         if (auto dir = to_passing_style(curr());
             dir != passing_style::invalid
             )
@@ -5841,6 +5843,23 @@ class parser
             next();
         }
 
+        //  Before the main declaration
+        //  If we're not at an identifier, backtrack to a parsed one.
+        if (curr().type() != lexeme::Identifier && curr().type() != lexeme::Keyword) {
+            if (pos != parameter_direction_pos)
+            {
+                n->pass = passing_style::in;
+                pos = parameter_direction_pos;
+            }
+            else if (pos != this_specifier_pos)
+            {
+                auto mod = std::exchange(n->mod, parameter_declaration_node::modifier::none);
+                pos = this_specifier_pos;
+                if (mod == parameter_declaration_node::modifier::virtual_) {
+                    error("invalid parameter identifier");
+                }
+            }
+        }
         //  Now the main declaration
         //
         if (!(n->declaration = declaration(false, true, is_template))) {