viml/parser/expressions: Highlight prefix separately from number

Should make accidental octals more visible.

src/nvim/viml/parser/expressions.c

@@ -1042,6 +1042,7 @@ void viml_pexpr_free_ast(ExprAST ast)
 //
 // NVimRegister -> SpecialChar
 // NVimNumber -> Number
+// NVimNumberPrefix -> SpecialChar
 // NVimFloat -> NVimNumber
 //
 // NVimNestingParenthesis -> NVimParenthesis
@@ -1842,6 +1843,14 @@ static const int want_node_to_lexer_flags[] = {
   [kENodeArgumentSeparator] = kELFlagForbidScope,
 };
 
+/// Number of characters to highlight as NumberPrefix depending on the base
+static const uint8_t base_to_prefix_length[] = {
+  [2] = 2,
+  [8] = 1,
+  [10] = 0,
+  [16] = 2,
+};
+
 /// Parse one VimL expression
 ///
 /// @param  pstate  Parser state.
@@ -2632,7 +2641,13 @@ viml_pexpr_parse_figure_brace_closing_error:
         } else {
           NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeInteger);
           cur_node->data.num.value = cur_token.data.num.val.integer;
-          HL_CUR_TOKEN(Number);
+          const uint8_t prefix_length = base_to_prefix_length[
+              cur_token.data.num.base];
+          viml_parser_highlight(pstate, cur_token.start, prefix_length,
+                                HL(NumberPrefix));
+          viml_parser_highlight(
+              pstate, shifted_pos(cur_token.start, prefix_length),
+              cur_token.len - prefix_length, HL(Number));
         }
         want_node = kENodeOperator;
         *top_node_p = cur_node;

test/unit/viml/expressions/parser_spec.lua

@@ -6858,6 +6858,116 @@ describe('Expressions parser', function()
       hl('Number', '2'),
     })
   end)
+  itp('highlights numbers with prefix', function()
+    check_parsing('0xABCDEF', 0, {
+      --           01234567
+      ast = {
+        'Integer(val=11259375):0:0:0xABCDEF',
+      },
+    }, {
+      hl('NumberPrefix', '0x'),
+      hl('Number', 'ABCDEF'),
+    })
+
+    check_parsing('0Xabcdef', 0, {
+      --           01234567
+      ast = {
+        'Integer(val=11259375):0:0:0Xabcdef',
+      },
+    }, {
+      hl('NumberPrefix', '0X'),
+      hl('Number', 'abcdef'),
+    })
+
+    check_parsing('0XABCDEF', 0, {
+      --           01234567
+      ast = {
+        'Integer(val=11259375):0:0:0XABCDEF',
+      },
+    }, {
+      hl('NumberPrefix', '0X'),
+      hl('Number', 'ABCDEF'),
+    })
+
+    check_parsing('0xabcdef', 0, {
+      --           01234567
+      ast = {
+        'Integer(val=11259375):0:0:0xabcdef',
+      },
+    }, {
+      hl('NumberPrefix', '0x'),
+      hl('Number', 'abcdef'),
+    })
+
+    check_parsing('0b001', 0, {
+      --           01234
+      ast = {
+        'Integer(val=1):0:0:0b001',
+      },
+    }, {
+      hl('NumberPrefix', '0b'),
+      hl('Number', '001'),
+    })
+
+    check_parsing('0B001', 0, {
+      --           01234
+      ast = {
+        'Integer(val=1):0:0:0B001',
+      },
+    }, {
+      hl('NumberPrefix', '0B'),
+      hl('Number', '001'),
+    })
+
+    check_parsing('0B00', 0, {
+      --           0123
+      ast = {
+        'Integer(val=0):0:0:0B00',
+      },
+    }, {
+      hl('NumberPrefix', '0B'),
+      hl('Number', '00'),
+    })
+
+    check_parsing('00', 0, {
+      --           01
+      ast = {
+        'Integer(val=0):0:0:00',
+      },
+    }, {
+      hl('NumberPrefix', '0'),
+      hl('Number', '0'),
+    })
+
+    check_parsing('001', 0, {
+      --           012
+      ast = {
+        'Integer(val=1):0:0:001',
+      },
+    }, {
+      hl('NumberPrefix', '0'),
+      hl('Number', '01'),
+    })
+
+    check_parsing('01', 0, {
+      --           01
+      ast = {
+        'Integer(val=1):0:0:01',
+      },
+    }, {
+      hl('NumberPrefix', '0'),
+      hl('Number', '1'),
+    })
+
+    check_parsing('1', 0, {
+      --           0
+      ast = {
+        'Integer(val=1):0:0:1',
+      },
+    }, {
+      hl('Number', '1'),
+    })
+  end)
   itp('works (KLEE tests)', function()
     check_parsing('\0002&A:\000', 0, {
       ast = nil,
@@ -6879,7 +6989,8 @@ describe('Expressions parser', function()
         'Integer(val=0):0:0:00',
       },
     }, {
-      hl('Number', '00'),
+      hl('NumberPrefix', '0'),
+      hl('Number', '0'),
     })
   end)
 end)