Improve diagnostics for forward return, closes #1072

Author: hsutter

regression-tests/test-results/pure2-forward-return-diagnostics-error.cpp2.output

@@ -1,24 +1,24 @@
 pure2-forward-return-diagnostics-error.cpp2...
-pure2-forward-return-diagnostics-error.cpp2(1,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(2,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(3,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(4,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(5,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(6,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(7,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(8,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(9,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(10,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(11,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(12,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(13,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(14,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(15,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(16,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(17,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(18,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(19,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(20,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(21,28): error: a 'forward' return type cannot return a temporary variable
-pure2-forward-return-diagnostics-error.cpp2(22,28): error: a 'forward' return type cannot return a temporary variable
+pure2-forward-return-diagnostics-error.cpp2(1,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(2,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(3,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(4,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(5,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(6,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(7,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(8,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(9,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(10,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(11,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(12,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(13,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(14,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(15,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(16,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(17,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(18,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(19,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(20,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(21,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
+pure2-forward-return-diagnostics-error.cpp2(22,28): error: a 'forward' return type must return an 'inout', 'out', or 'forward' parameter; it cannot return a complex expression -- for example: for a function that takes a stream object 'output`, instead of 'return output << data;' write 'output << data; return output;'
 

source/parse.h

@@ -2479,6 +2479,18 @@ struct function_type_node
         return has_parameter_with_name_and_pass(s, passing_style::in);
     }
 
+    auto has_copy_parameter_named(std::string_view s) const
+        -> bool
+    {
+        return has_parameter_with_name_and_pass(s, passing_style::copy);
+    }
+
+    auto has_inout_parameter_named(std::string_view s) const
+        -> bool
+    {
+        return has_parameter_with_name_and_pass(s, passing_style::inout);
+    }
+
     auto has_out_parameter_named(std::string_view s) const
         -> bool
     {
@@ -2491,6 +2503,12 @@ struct function_type_node
         return has_parameter_with_name_and_pass(s, passing_style::move);
     }
 
+    auto has_forward_parameter_named(std::string_view s) const
+        -> bool
+    {
+        return has_parameter_with_name_and_pass(s, passing_style::forward);
+    }
+
     //  Internals
     //
     auto position() const
@@ -2923,6 +2941,24 @@ struct declaration_node
         return std::get<a_function>(type)->has_in_parameter_named(s);
     }
 
+    auto has_copy_parameter_named(std::string_view s) const
+        -> bool
+    {
+        if (!is_function()) {
+            return false;
+        }
+        return std::get<a_function>(type)->has_copy_parameter_named(s);
+    }
+
+    auto has_inout_parameter_named(std::string_view s) const
+        -> bool
+    {
+        if (!is_function()) {
+            return false;
+        }
+        return std::get<a_function>(type)->has_inout_parameter_named(s);
+    }
+
     auto has_out_parameter_named(std::string_view s) const
         -> bool
     {
@@ -2941,6 +2977,15 @@ struct declaration_node
         return std::get<a_function>(type)->has_move_parameter_named(s);
     }
 
+    auto has_forward_parameter_named(std::string_view s) const
+        -> bool
+    {
+        if (!is_function()) {
+            return false;
+        }
+        return std::get<a_function>(type)->has_forward_parameter_named(s);
+    }
+
     auto nth_parameter_type_name(int n) const
         -> std::string
     {