fix: fix incorrect syntax highlighting

Syntax highlighting is still not 100% accurate (due mostly to
highlighting differences between different languages which require
particular consideration), however, the accuracy of the highlights have
been improved, both overall, and in terms of common languages such as:
rust, ruby, ecma, c, c#, go, html, css, make, python, and lua.

Fixes projekt0n#252

lua/github-theme/group/syntax.lua

@@ -4,6 +4,33 @@ function M.get(spec, config)
   local syn = spec.syntax
   local stl = config.styles
 
+  ---Clears nvim's default highlighting for a highlight-group and allows
+  ---falling-back to another hl-group when multiple highlights/groups are
+  ---assigned/stacked at a particular screen position. This is just an empty
+  ---table.
+  ---
+  ---NOTE: assigning this to a group is different from explicitly setting a
+  ---group's foreground color to the global/default foreground color. When
+  ---multiple highlights are stacked/assigned to the same screen position, this
+  ---will allow the other highlights/groups to take effect, whereas explicitly
+  ---setting a hl-group's `fg` will not. In some cases, this effect is desirable
+  ---(e.g. `['@constructor.ecma'] = NONE` which allows the `constructor` in
+  ---`constructor() {}` to fallback to the `@method` hl-group), while in other
+  ---cases, it may not be.
+  ---
+  ---|                           Setting                            | Fallback |
+  ---| ------------------------------------------------------------ | -------- |
+  ---| `GROUP = FALLBACK_OR_NONE` (i.e. set to this variable) (Lua) |   true   |
+  ---| Link to `@none`, `Fg`, or `NONE`                             |   true   |
+  ---| `GROUP = { fg = DEFAULT_FG }` (Lua)                          |   false  |
+  ---| `hi! clear GROUP` (Vim command)                              |   false  |
+  ---| `hi! GROUP NONE` (Vim command)                               |   false  |
+  local FALLBACK_OR_NONE = setmetatable({}, {
+    __newindex = function()
+      error('attempt to set index of readonly table', 2)
+    end,
+  })
+
   -- TODO:
   -- (1) add Commented style settings in config module
   -- stylua: ignore
@@ -39,6 +66,7 @@ function M.get(spec, config)
     -- Structure      = { link = 'Type' }, -- struct, union, enum, etc.
     -- Typedef        = { link = 'Type' }, -- A typedef
 
+    Special        = { fg = spec.fg1 }, -- (preferred) any special symbol
     -- Special        = { fg = syn.ident }, -- (preferred) any special symbol
     -- SpecialChar    = { link = 'Special' }, -- special character in a constant
     -- Tag            = { link = 'Special' }, -- you can use CTRL-] on this

lua/github-theme/palette/github_dark.lua

@@ -5,6 +5,11 @@ local meta = {
   light = false,
 }
 
+local primitives =
+  require('github-theme.palette.primitives.' .. meta.name:gsub('^github%W*', '', 1))
+
+local pl = primitives.prettylights
+
 ---Github Dark scale variables
 ---source: https://github.com/primer/primitives/blob/main/data/colors/themes/dark.ts
 -- stylua: ignore
@@ -192,18 +197,18 @@ local function generate_spec(pal)
     conditional = pal.scale.red[4],                  -- Conditional and loop
     const       = pal.scale.blue[3],                 -- Constants, imports and booleans
     dep         = pal.scale.red[3],                  -- Deprecated
-    field       = pal.scale.purple[3],               -- Field
+    field       = pl.syntax.constant,                -- Field
     func        = pal.scale.purple[2],               -- Functions and Titles
     ident       = pal.scale.blue[3],                 -- Identifiers
     keyword     = pal.scale.red[4],                  -- Keywords
     number      = pal.scale.blue[3],                 -- Numbers
-    operator    = pal.scale.red[4],                  -- Operators
-    param       = pal.scale.green[2],                -- Parameters
+    operator    = pl.syntax.constant,                -- Operators
+    param       = spec.fg1,                          -- Parameters
     preproc     = pal.scale.red[4],                  -- PreProc
     regex       = pal.scale.blue[3],                 -- Regex
     statement   = pal.scale.red[4],                  -- Statements
     string      = pal.scale.blue[2],                 -- Strings
-    type        = pal.scale.red[4],                  -- Types
+    type        = pl.syntax.variable,                -- Types
     tag         = pal.scale.green[2],                -- Tags
     variable    = spec.fg1,                          -- Variables
   }
@@ -241,4 +246,9 @@ local function generate_spec(pal)
   return spec
 end
 
-return { meta = meta, palette = palette, generate_spec = generate_spec }
+return {
+  meta = meta,
+  primitives = primitives,
+  palette = palette,
+  generate_spec = generate_spec,
+}

lua/github-theme/palette/github_dark_colorblind.lua

@@ -5,6 +5,11 @@ local meta = {
   light = false,
 }
 
+local primitives =
+  require('github-theme.palette.primitives.' .. meta.name:gsub('^github%W*', '', 1))
+
+local pl = primitives.prettylights
+
 ---Github Dark Colorblind scale variables
 ---source: https://github.com/primer/primitives/blob/main/data/colors/themes/dark_colorblind.ts
 -- stylua: ignore
@@ -192,18 +197,18 @@ local function generate_spec(pal)
     conditional = pal.scale.red[4],                  -- Conditional and loop
     const       = pal.scale.blue[3],                 -- Constants, imports and booleans
     dep         = pal.scale.red[3],                  -- Deprecated
-    field       = pal.scale.orange[3],               -- Field
+    field       = pl.syntax.constant,                -- Field
     func        = pal.scale.purple[3],               -- Functions and Titles
     ident       = pal.scale.blue[3],                 -- Identifiers
     keyword     = pal.scale.red[4],                  -- Keywords
     number      = pal.scale.blue[3],                 -- Numbers
-    operator    = pal.scale.red[4],                  -- Operators
-    param       = pal.scale.orange[2],               -- Parameters
+    operator    = pl.syntax.constant,                -- Operators
+    param       = spec.fg1,                          -- Parameters
     preproc     = pal.scale.red[4],                  -- PreProc
     regex       = pal.scale.blue[3],                 -- Regex
     statement   = pal.scale.red[4],                  -- Statements
     string      = pal.scale.blue[2],                 -- Strings
-    type        = pal.scale.orange[3],               -- Types
+    type        = pl.syntax.variable,                -- Types
     tag         = pal.scale.blue[3],                 -- Tags
     variable    = spec.fg1,                          -- Variables
   }
@@ -241,4 +246,9 @@ local function generate_spec(pal)
   return spec
 end
 
-return { meta = meta, palette = palette, generate_spec = generate_spec }
+return {
+  meta = meta,
+  primitives = primitives,
+  palette = palette,
+  generate_spec = generate_spec,
+}

lua/github-theme/palette/github_dark_dimmed.lua

@@ -5,6 +5,11 @@ local meta = {
   light = false,
 }
 
+local primitives =
+  require('github-theme.palette.primitives.' .. meta.name:gsub('^github%W*', '', 1))
+
+local pl = primitives.prettylights
+
 ---Github Dark Dimmed scale variables
 ---source: https://github.com/primer/primitives/blob/main/data/colors/themes/dark_dimmed.ts
 -- stylua: ignore
@@ -184,26 +189,26 @@ local function generate_spec(pal)
   }
 
   spec.syntax = {
-    bracket     = pal.scale.green[4],                -- Brackets and Punctuation
+    bracket     = spec.fg1,                          -- Brackets and Punctuation
     builtin0    = pal.scale.red[4],                  -- Builtin variable (Return Keywords, Regex, etc.)
     builtin1    = pal.scale.red[4],                  -- Builtin type
     builtin2    = pal.scale.blue[3],                 -- Builtin const
     comment     = pal.scale.gray[5],                 -- Comment
     conditional = pal.scale.red[4],                  -- Conditional and loop
     const       = pal.scale.blue[3],                 -- Constants, imports and booleans
     dep         = pal.scale.red[3],                  -- Deprecated
-    field       = pal.scale.purple[3],               -- Field
+    field       = pl.syntax.constant,                -- Field
     func        = pal.scale.purple[2],               -- Functions and Titles
     ident       = pal.scale.blue[3],                 -- Identifiers
     keyword     = pal.scale.red[4],                  -- Keywords
     number      = pal.scale.blue[3],                 -- Numbers
-    operator    = pal.scale.red[4],                  -- Operators
-    param       = pal.scale.orange[3],               -- Parameters
+    operator    = pl.syntax.constant,                -- Operators
+    param       = spec.fg1,                          -- Parameters
     preproc     = pal.scale.red[4],                  -- PreProc
     regex       = pal.scale.blue[3],                 -- Regex
     statement   = pal.scale.red[4],                  -- Statements
     string      = pal.scale.blue[2],                 -- Strings
-    type        = pal.scale.red[4],                  -- Types
+    type        = pl.syntax.variable,                -- Types
     tag         = pal.scale.green[2],                -- Tags
     variable    = spec.fg1,                          -- Variables
   }
@@ -241,4 +246,9 @@ local function generate_spec(pal)
   return spec
 end
 
-return { meta = meta, palette = palette, generate_spec = generate_spec }
+return {
+  meta = meta,
+  primitives = primitives,
+  palette = palette,
+  generate_spec = generate_spec,
+}

lua/github-theme/palette/github_dark_high_contrast.lua

@@ -5,6 +5,11 @@ local meta = {
   light = false,
 }
 
+local primitives =
+  require('github-theme.palette.primitives.' .. meta.name:gsub('^github%W*', '', 1))
+
+local pl = primitives.prettylights
+
 ---Github Dark High Contrast scale variables
 ---source: https://github.com/primer/primitives/blob/main/data/colors/themes/dark_high_contrast.ts
 -- stylua: ignore
@@ -192,18 +197,18 @@ local function generate_spec(pal)
     conditional = pal.scale.red[4],                  -- Conditional and loop
     const       = pal.scale.blue[3],                 -- Constants, imports and booleans
     dep         = pal.scale.red[3],                  -- Deprecated
-    field       = pal.scale.purple[3],               -- Field
+    field       = pl.syntax.constant,                -- Field
     func        = pal.scale.purple[2],               -- Functions and Titles
     ident       = pal.scale.blue[3],                 -- Identifiers
     keyword     = pal.scale.red[4],                  -- Keywords
     number      = pal.scale.blue[3],                 -- Numbers
-    operator    = pal.scale.red[4],                  -- Operators
-    param       = pal.scale.orange[3],               -- Parameters
+    operator    = pl.syntax.constant,                -- Operators
+    param       = spec.fg1,                          -- Parameters
     preproc     = pal.scale.red[4],                  -- PreProc
     regex       = pal.scale.blue[3],                 -- Regex
     statement   = pal.scale.red[4],                  -- Statements
     string      = pal.scale.blue[2],                 -- Strings
-    type        = pal.scale.red[4],                  -- Types
+    type        = pl.syntax.variable,                -- Types
     tag         = pal.scale.green[2],                -- Tags
     variable    = spec.fg1,                          -- Variables
   }
@@ -241,4 +246,9 @@ local function generate_spec(pal)
   return spec
 end
 
-return { meta = meta, palette = palette, generate_spec = generate_spec }
+return {
+  meta = meta,
+  primitives = primitives,
+  palette = palette,
+  generate_spec = generate_spec,
+}

lua/github-theme/palette/github_dark_tritanopia.lua

@@ -5,6 +5,11 @@ local meta = {
   light = false,
 }
 
+local primitives =
+  require('github-theme.palette.primitives.' .. meta.name:gsub('^github%W*', '', 1))
+
+local pl = primitives.prettylights
+
 ---Github Dark Tritanopia scale variables
 ---source: https://github.com/primer/primitives/blob/main/data/colors/themes/dark_tritanopia.ts
 -- stylua: ignore
@@ -192,18 +197,18 @@ local function generate_spec(pal)
     conditional = pal.scale.red[4],                  -- Conditional and loop
     const       = pal.scale.blue[3],                 -- Constants, imports and booleans
     dep         = pal.scale.red[3],                  -- Deprecated
-    field       = pal.scale.orange[3],               -- Field
+    field       = pl.syntax.constant,                -- Field
     func        = pal.scale.purple[3],               -- Functions and Titles
     ident       = pal.scale.blue[3],                 -- Identifiers
     keyword     = pal.scale.red[4],                  -- Keywords
     number      = pal.scale.blue[3],                 -- Numbers
-    operator    = pal.scale.red[4],                  -- Operators
-    param       = pal.scale.orange[2],               -- Parameters
+    operator    = pl.syntax.constant,                -- Operators
+    param       = spec.fg1,                          -- Parameters
     preproc     = pal.scale.red[4],                  -- PreProc
     regex       = pal.scale.blue[3],                 -- Regex
     statement   = pal.scale.red[4],                  -- Statements
     string      = pal.scale.blue[2],                 -- Strings
-    type        = pal.scale.orange[3],               -- Types
+    type        = pl.syntax.variable,                -- Types
     tag         = pal.scale.blue[3],                 -- Tags
     variable    = spec.fg1,                          -- Variables
   }
@@ -241,4 +246,9 @@ local function generate_spec(pal)
   return spec
 end
 
-return { meta = meta, palette = palette, generate_spec = generate_spec }
+return {
+  meta = meta,
+  primitives = primitives,
+  palette = palette,
+  generate_spec = generate_spec,
+}

lua/github-theme/palette/github_light.lua

@@ -5,6 +5,11 @@ local meta = {
   light = true,
 }
 
+local primitives =
+  require('github-theme.palette.primitives.' .. meta.name:gsub('^github%W*', '', 1))
+
+local pl = primitives.prettylights
+
 ---Github Light scale variables
 ---source: https://github.com/primer/primitives/blob/main/data/colors/themes/light.ts
 -- stylua: ignore
@@ -185,26 +190,26 @@ local function generate_spec(pal)
   }
 
   spec.syntax = {
-    bracket     = pal.scale.orange[5],                  -- Brackets and Punctuation
+    bracket     = spec.fg1,                             -- Brackets and Punctuation
     builtin0    = pal.scale.red[6],                     -- Builtin variable
     builtin1    = pal.scale.red[6],                     -- Builtin type
     builtin2    = pal.scale.blue[7],                    -- Builtin const
     comment     = pal.scale.gray[6],                    -- Comment
     conditional = pal.scale.red[6],                     -- Conditional and loop
     const       = pal.scale.blue[6],                    -- Constants, imports and booleans
     dep         = pal.scale.red[8],                     -- Deprecated
-    field       = spec.fg1,                             -- Field
+    field       = pl.syntax.constant,                   -- Field
     func        = pal.scale.purple[6],                  -- Functions and Titles
     ident       = pal.scale.blue[9],                    -- Identifiers
     keyword     = pal.scale.red[6],                     -- Keywords
     number      = pal.scale.blue[7],                    -- Numbers
-    operator    = pal.scale.red[6],                     -- Operators
-    param       = pal.scale.orange[5],                  -- PreProc
+    operator    = pl.syntax.constant,                   -- Operators
+    param       = spec.fg1,                             -- Parameters
     preproc     = pal.scale.red[6],                     -- PreProc
     regex       = pal.scale.blue[9],                    -- Regex
     statement   = pal.scale.red[6],                     -- Statements
     string      = pal.scale.blue[8],                    -- Strings
-    type        = pal.scale.red[6],                     -- Types
+    type        = pl.syntax.variable,                   -- Types
     tag         = pal.scale.green[6],                   -- Tags
     variable    = spec.fg1,                             -- Variables
   }
@@ -242,4 +247,9 @@ local function generate_spec(pal)
   return spec
 end
 
-return { meta = meta, palette = palette, generate_spec = generate_spec }
+return {
+  meta = meta,
+  primitives = primitives,
+  palette = palette,
+  generate_spec = generate_spec,
+}

lua/github-theme/palette/github_light_colorblind.lua

@@ -5,6 +5,11 @@ local meta = {
   light = true,
 }
 
+local primitives =
+  require('github-theme.palette.primitives.' .. meta.name:gsub('^github%W*', '', 1))
+
+local pl = primitives.prettylights
+
 ---Github Light scale variables
 ---source: https://github.com/primer/primitives/blob/main/data/colors/themes/light_colorblind.ts
 -- stylua: ignore
@@ -193,18 +198,18 @@ local function generate_spec(pal)
     conditional = pal.scale.red[6],                     -- Conditional and loop
     const       = pal.scale.blue[6],                    -- Constants, imports and booleans
     dep         = pal.scale.red[8],                     -- Deprecated
-    field       = pal.scale.orange[8],                  -- Field
+    field       = pl.syntax.constant,                   -- Field
     func        = pal.scale.purple[6],                  -- Functions and Titles
     ident       = pal.scale.blue[9],                    -- Identifiers
     keyword     = pal.scale.red[6],                     -- Keywords
     number      = pal.scale.blue[7],                    -- Numbers
-    operator    = pal.scale.red[6],                     -- Operators
-    param       = pal.scale.orange[5],                  -- PreProc
+    operator    = pl.syntax.constant,                   -- Operators
+    param       = spec.fg1,                             -- Parameters
     preproc     = pal.scale.red[6],                     -- PreProc
     regex       = pal.scale.blue[9],                    -- Regex
     statement   = pal.scale.red[6],                     -- Statements
     string      = pal.scale.blue[8],                    -- Strings
-    type        = pal.scale.orange[5],                  -- Types
+    type        = pl.syntax.variable,                   -- Types
     tag         = pal.scale.green[6],                   -- Tags
     variable    = spec.fg1,                             -- Variables
   }
@@ -242,4 +247,9 @@ local function generate_spec(pal)
   return spec
 end
 
-return { meta = meta, palette = palette, generate_spec = generate_spec }
+return {
+  meta = meta,
+  primitives = primitives,
+  palette = palette,
+  generate_spec = generate_spec,
+}