Make doxygen happy.

This CL adds some code comments to fixup doxygen warnings.

Change-Id: I0d0f4b20a1023691141b2f49f82f4538ffe18614
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/31600
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: dan sinclair <dsinclair@chromium.org>

src/source.h

@@ -30,19 +30,26 @@ class Source {
   class File {
    public:
     /// Constructs the File with the given file path and content.
+    /// @param file_path the path for this file
+    /// @param file_content the file contents
     File(const std::string& file_path, const std::string& file_content);
     ~File();
 
-    const std::string path;                /// file path (optional)
-    const std::string content;             /// file content
-    const std::vector<std::string> lines;  /// |content| split by lines
+    /// file path (optional)
+    const std::string path;
+    /// file content
+    const std::string content;
+    /// |content| split by lines
+    const std::vector<std::string> lines;
   };
 
   /// Location holds a 1-based line and column index.
   /// 0's for |line| or |column| represent invalid values.
   class Location {
    public:
+    /// The line number, 1-based
     size_t line = 0;
+    /// The column number, 1-based
     size_t column = 0;
   };
 
@@ -53,28 +60,39 @@ class Source {
     inline Range() = default;
 
     /// Constructs a zero-length Range starting at |loc|.
+    /// @param loc the location to use to build the range
     inline explicit Range(const Location& loc) : begin(loc), end(loc) {}
 
     /// Constructs the Range beginning at |b| and ending at |e|.
+    /// @param b the beginning of the range
+    /// @param e the end of the range
     inline Range(const Location& b, const Location& e) : begin(b), end(e) {}
 
-    Location begin;  /// The location of the first character in the range.
-    Location end;  /// The location of one-past the last character in the range.
+    /// The location of the first character in the range.
+    Location begin;
+    /// The location of one-past the last character in the range.
+    Location end;
   };
 
   /// Constructs the Source with an zero initialized Range and null File.
   inline Source() = default;
 
   /// Constructs the Source with the Range |rng| and a null File.
+  /// @param rng the range to assign to the source
   inline explicit Source(const Range& rng) : range(rng) {}
 
   /// Constructs the Source with the Range |loc| and a null File.
+  /// @param loc the location to assign to the source
   inline explicit Source(const Location& loc) : range(Range(loc)) {}
 
   /// Constructs the Source with the Range |rng| and File |f|.
+  /// @param rng the range for the source
+  /// @param f the file for the source
   inline Source(const Range& rng, File const* f) : range(rng), file(f) {}
 
+  /// Line/column range for this source
   Range range;
+  /// Source file
   File const* file = nullptr;
 };