Doxygen cleanup

This CL suppresses some Doxygen warnings for code doxygen doesn't
process correctly and adds the missing return for GenerateEntryPoint
method.

Change-Id: If97443a7177caa51c1054de83fb0711692a7ab22
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/29461
Commit-Queue: dan sinclair <dsinclair@chromium.org>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Ryan Harrison <rharrison@chromium.org>

src/ast/function_decoration.h

@@ -42,7 +42,9 @@ class FunctionDecoration {
 
   /// Outputs the function decoration to the given stream
   /// @param out the stream to output too
+  //! @cond Doxygen_Suppress
   virtual void to_str(std::ostream& out) const = 0;
+  //! @endcond
 
  protected:
   FunctionDecoration();

src/ast/node.h

@@ -45,7 +45,9 @@ class Node {
   /// Writes a representation of the node to the output stream
   /// @param out the stream to write to
   /// @param indent number of spaces to indent the node when writing
+  //! @cond Doxygen_Suppress
   virtual void to_str(std::ostream& out, size_t indent) const = 0;
+  //! @endcond
 
   /// Convenience wrapper around the |to_str| method.
   /// @returns the node as a string

src/ast/variable_decoration.h

@@ -58,7 +58,9 @@ class VariableDecoration {
 
   /// Outputs the variable decoration to the given stream
   /// @param out the stream to output too
+  //! @cond Doxygen_Suppress
   virtual void to_str(std::ostream& out) const = 0;
+  //! @endcond
 
  protected:
   VariableDecoration();

src/writer/wgsl/generator_impl.h

@@ -50,6 +50,7 @@ class GeneratorImpl : public TextGenerator {
   /// @param module the module to generate from
   /// @param stage the pipeline stage
   /// @param name the entry point name
+  /// @returns true on successful generation; false otherwise
   bool GenerateEntryPoint(const ast::Module& module,
                           ast::PipelineStage stage,
                           const std::string& name);

src/writer/writer.h

@@ -32,7 +32,9 @@ class Writer {
   const std::string& error() const { return error_; }
 
   /// Resets the generator
+  //! @cond Doxygen_Suppress
   virtual void Reset() = 0;
+  //! @endcond
 
   /// Converts the module into the desired format
   /// @returns true on success; false on failure