gccrs: diagnostics: Add underline for tokens in diagnostics.

Currently, the diagnostics only point to the corresponding token's
start position by carets, and lack of underlines for full token.  This
commit add support for such underlines in diagnostics by encoding range
information in location_t.

gcc/rust/ChangeLog:

	* lex/rust-lex.cc (Lexer::build_token): Make location enclose entire token.
	(Lexer::parse_byte_char): Likewise.
	(Lexer::parse_byte_string): Likewise.
	(Lexer::parse_raw_byte_string): Likewise.
	(Lexer::parse_raw_identifier): Likewise.
	(Lexer::parse_string): Likewise.
	(Lexer::parse_identifier_or_keyword): Likewise.
	(Lexer::parse_raw_string): Likewise.
	(Lexer::parse_non_decimal_int_literal): Likewise.
	(Lexer::parse_decimal_int_or_float): Likewise.
	(Lexer::parse_char_or_lifetime): Likewise.

gcc/testsuite/ChangeLog:

	* rust/compile/diagnostic_underline.rs: New test.

Signed-off-by: Xiao Ma <mxlol233@outlook.com>

gcc/rust/lex/rust-lex.cc

@@ -447,6 +447,7 @@ Lexer::build_token ()
 	      // match arm arrow
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (MATCH_ARROW, loc);
 	    }
@@ -455,6 +456,7 @@ Lexer::build_token ()
 	      // equality operator
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (EQUAL_EQUAL, loc);
 	    }
@@ -473,6 +475,7 @@ Lexer::build_token ()
 	      // return type specifier
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (RETURN_TYPE, loc);
 	    }
@@ -481,6 +484,7 @@ Lexer::build_token ()
 	      // minus-assign
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (MINUS_EQ, loc);
 	    }
@@ -496,6 +500,7 @@ Lexer::build_token ()
 	      // add-assign
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (PLUS_EQ, loc);
 	    }
@@ -517,6 +522,7 @@ Lexer::build_token ()
 	      // multiplication-assign
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (ASTERISK_EQ, loc);
 	    }
@@ -535,6 +541,7 @@ Lexer::build_token ()
 	      // division-assign
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (DIV_EQ, loc);
 	    }
@@ -602,6 +609,8 @@ Lexer::build_token ()
 	      start_line (current_line, max_column_hint);
 
 	      str.shrink_to_fit ();
+
+	      loc += str.size () - 1;
 	      if (is_inner)
 		return Token::make_inner_doc_comment (loc, std::move (str));
 	      else
@@ -756,6 +765,8 @@ Lexer::build_token ()
 		}
 
 	      str.shrink_to_fit ();
+
+	      loc += str.size () - 1;
 	      if (is_inner)
 		return Token::make_inner_doc_comment (loc, std::move (str));
 	      else
@@ -773,6 +784,7 @@ Lexer::build_token ()
 	      // modulo-assign
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (PERCENT_EQ, loc);
 	    }
@@ -788,6 +800,7 @@ Lexer::build_token ()
 	      // xor-assign?
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (CARET_EQ, loc);
 	    }
@@ -805,6 +818,7 @@ Lexer::build_token ()
 		  // left-shift assign
 		  skip_input (1);
 		  current_column += 3;
+		  loc += 2;
 
 		  return Token::make (LEFT_SHIFT_EQ, loc);
 		}
@@ -813,6 +827,7 @@ Lexer::build_token ()
 		  // left-shift
 		  skip_input ();
 		  current_column += 2;
+		  loc += 1;
 
 		  return Token::make (LEFT_SHIFT, loc);
 		}
@@ -822,6 +837,7 @@ Lexer::build_token ()
 	      // smaller than or equal to
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (LESS_OR_EQUAL, loc);
 	    }
@@ -840,6 +856,7 @@ Lexer::build_token ()
 		  // right-shift-assign
 		  skip_input (1);
 		  current_column += 3;
+		  loc += 2;
 
 		  return Token::make (RIGHT_SHIFT_EQ, loc);
 		}
@@ -848,6 +865,7 @@ Lexer::build_token ()
 		  // right-shift
 		  skip_input ();
 		  current_column += 2;
+		  loc += 1;
 
 		  return Token::make (RIGHT_SHIFT, loc);
 		}
@@ -857,6 +875,7 @@ Lexer::build_token ()
 	      // larger than or equal to
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (GREATER_OR_EQUAL, loc);
 	    }
@@ -872,6 +891,7 @@ Lexer::build_token ()
 	      // scope resolution ::
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (SCOPE_RESOLUTION, loc);
 	    }
@@ -888,6 +908,7 @@ Lexer::build_token ()
 	      // not equal boolean operator
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (NOT_EQUAL, loc);
 	    }
@@ -937,6 +958,7 @@ Lexer::build_token ()
 	      // bitwise or-assign?
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (PIPE_EQ, loc);
 	    }
@@ -945,6 +967,7 @@ Lexer::build_token ()
 	      // logical or
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (OR, loc);
 	    }
@@ -961,6 +984,7 @@ Lexer::build_token ()
 	      // bitwise and-assign?
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (AMP_EQ, loc);
 	    }
@@ -969,6 +993,7 @@ Lexer::build_token ()
 	      // logical and
 	      skip_input ();
 	      current_column += 2;
+	      loc += 1;
 
 	      return Token::make (LOGICAL_AND, loc);
 	    }
@@ -987,6 +1012,7 @@ Lexer::build_token ()
 		  // ellipsis
 		  skip_input (1);
 		  current_column += 3;
+		  loc += 2;
 
 		  return Token::make (ELLIPSIS, loc);
 		}
@@ -995,6 +1021,7 @@ Lexer::build_token ()
 		  // ..=
 		  skip_input (1);
 		  current_column += 3;
+		  loc += 2;
 
 		  return Token::make (DOT_DOT_EQ, loc);
 		}
@@ -1003,6 +1030,7 @@ Lexer::build_token ()
 		  // ..
 		  skip_input ();
 		  current_column += 2;
+		  loc += 1;
 
 		  return Token::make (DOT_DOT, loc);
 		}
@@ -1717,6 +1745,8 @@ Lexer::parse_byte_char (Location loc)
 
   current_column += length;
 
+  loc += length - 1;
+
   return Token::make_byte_char (loc, byte_char);
 }
 
@@ -1781,6 +1811,7 @@ Lexer::parse_byte_string (Location loc)
     }
 
   str.shrink_to_fit ();
+  loc += str.size () - 1;
 
   return Token::make_byte_string (loc, std::move (str));
 }
@@ -1861,6 +1892,8 @@ Lexer::parse_raw_byte_string (Location loc)
 
   current_column += length;
 
+  loc += length - 1;
+
   str.shrink_to_fit ();
 
   return Token::make_byte_string (loc, std::move (str));
@@ -1912,6 +1945,7 @@ Lexer::parse_raw_identifier (Location loc)
   else
     {
       str.shrink_to_fit ();
+      loc += length - 1;
 
       return Token::make_identifier (loc, std::move (str));
     }
@@ -2009,6 +2043,8 @@ Lexer::parse_string (Location loc)
     }
 
   str.shrink_to_fit ();
+  loc += length - 1;
+
   return Token::make_string (loc, std::move (str));
 }
 
@@ -2043,6 +2079,8 @@ Lexer::parse_identifier_or_keyword (Location loc)
 
   str.shrink_to_fit ();
 
+  loc += length - 1;
+
   TokenId keyword = classify_keyword (str);
   if (keyword == IDENTIFIER)
     return Token::make_identifier (loc, std::move (str));
@@ -2120,6 +2158,8 @@ Lexer::parse_raw_string (Location loc, int initial_hash_count)
 
   current_column += length;
 
+  loc += length - 1;
+
   str.shrink_to_fit ();
 
   return Token::make_string (loc, std::move (str));
@@ -2183,6 +2223,9 @@ Lexer::parse_non_decimal_int_literal (Location loc, IsDigitFunc is_digit_func,
 						 : "<insert unknown base>")));
       return nullptr;
     }
+
+  loc += length - 1;
+
   return Token::make_int (loc, std::move (existent_str), type_hint);
 }
 
@@ -2275,6 +2318,8 @@ Lexer::parse_decimal_int_or_float (Location loc)
 
       current_column += length;
 
+      loc += length - 1;
+
       str.shrink_to_fit ();
       return Token::make_float (loc, std::move (str), type_hint);
     }
@@ -2295,6 +2340,8 @@ Lexer::parse_decimal_int_or_float (Location loc)
 
       current_column += length;
 
+      loc += length - 1;
+
       str.shrink_to_fit ();
       return Token::make_float (loc, std::move (str), CORETYPE_UNKNOWN);
     }
@@ -2324,6 +2371,8 @@ Lexer::parse_decimal_int_or_float (Location loc)
 
       current_column += length;
 
+      loc += length - 1;
+
       str.shrink_to_fit ();
       return Token::make_float (loc, std::move (str), type_hint);
     }
@@ -2345,6 +2394,8 @@ Lexer::parse_decimal_int_or_float (Location loc)
 
       current_column += length;
 
+      loc += length - 1;
+
       str.shrink_to_fit ();
       return Token::make_int (loc, std::move (str), type_hint);
     }
@@ -2382,6 +2433,8 @@ Lexer::parse_char_or_lifetime (Location loc)
 
       current_column += length;
 
+      loc += length - 1;
+
       return Token::make_char (loc, current_char32);
     }
   else
@@ -2399,6 +2452,8 @@ Lexer::parse_char_or_lifetime (Location loc)
 	  // TODO fix due to different widths of utf-8 chars?
 	  current_column += 3;
 
+	  loc += 2;
+
 	  return Token::make_char (loc, current_char32);
 	}
       else if (ISDIGIT (current_char32.value) || ISALPHA (current_char32.value)
@@ -2421,6 +2476,8 @@ Lexer::parse_char_or_lifetime (Location loc)
 
 	  current_column += length;
 
+	  loc += length - 1;
+
 	  str.shrink_to_fit ();
 	  return Token::make_lifetime (loc, std::move (str));
 	}

gcc/testsuite/rust/compile/diagnostic_underline.rs

@@ -0,0 +1,15 @@
+// { dg-additional-options "-quiet" }
+
+/* { dg-options "-fdiagnostics-show-caret" } */
+
+
+fn barbarbar() {}
+
+const fn foo() { 
+    barbarbar();// { dg-error "only functions marked as 'const' are allowed to be called from constant contexts" }
+/* { dg-begin-multiline-output "" }
+     barbarbar();//
+     ^~~~~~~~~
+{ dg-end-multiline-output "" } */
+}
+