diff --git a/components/style/gecko/conversions.rs b/components/style/gecko/conversions.rs
index c00420e7b1d..7b89cb0cefb 100644
--- a/components/style/gecko/conversions.rs
+++ b/components/style/gecko/conversions.rs
@@ -18,7 +18,7 @@ use gecko_bindings::sugar::ns_style_coord::{CoordDataValue, CoordData, CoordData
 use std::f32::consts::PI;
 use stylesheets::{Origin, RulesMutateError};
 use values::computed::{Angle, CalcLengthOrPercentage, Gradient, Image};
-use values::computed::{LengthOrPercentage, LengthOrPercentageOrAuto, Percentage};
+use values::computed::{Integer, LengthOrPercentage, LengthOrPercentageOrAuto, Percentage};
 use values::generics::box_::VerticalAlign;
 use values::generics::grid::{TrackListValue, TrackSize};
 use values::generics::image::{CompatMode, Image as GenericImage, GradientItem};
@@ -896,7 +896,7 @@ impl TrackSize<LengthOrPercentage> {
     }
 }
 
-impl TrackListValue<LengthOrPercentage> {
+impl TrackListValue<LengthOrPercentage, Integer> {
     /// Return TrackSize from given two nsStyleCoord
     pub fn from_gecko_style_coords<T: CoordData>(gecko_min: &T, gecko_max: &T) -> Self {
         TrackListValue::TrackSize(TrackSize::from_gecko_style_coords(gecko_min, gecko_max))
diff --git a/components/style/properties/gecko.mako.rs b/components/style/properties/gecko.mako.rs
index fb59b00c704..a2d01bbf4ca 100644
--- a/components/style/properties/gecko.mako.rs
+++ b/components/style/properties/gecko.mako.rs
@@ -1700,7 +1700,7 @@ fn static_assert() {
         if let Some(integer) = v.line_num {
             // clamping the integer between a range
             self.gecko.${value.gecko}.mInteger = cmp::max(nsStyleGridLine_kMinLine,
-                cmp::min(integer.value(), nsStyleGridLine_kMaxLine));
+                cmp::min(integer, nsStyleGridLine_kMaxLine));
         }
     }
 
@@ -1717,7 +1717,6 @@ fn static_assert() {
     pub fn clone_${value.name}(&self) -> longhands::${value.name}::computed_value::T {
         use gecko_bindings::structs::{nsStyleGridLine_kMinLine, nsStyleGridLine_kMaxLine};
         use string_cache::Atom;
-        use values::specified::Integer;
 
         longhands::${value.name}::computed_value::T {
             is_span: self.gecko.${value.gecko}.mHasSpan,
@@ -1735,7 +1734,7 @@ fn static_assert() {
                 } else {
                     debug_assert!(nsStyleGridLine_kMinLine <= self.gecko.${value.gecko}.mInteger);
                     debug_assert!(self.gecko.${value.gecko}.mInteger <= nsStyleGridLine_kMaxLine);
-                    Some(Integer::new(self.gecko.${value.gecko}.mInteger))
+                    Some(self.gecko.${value.gecko}.mInteger)
                 },
         }
     }
diff --git a/components/style/properties/shorthand/position.mako.rs b/components/style/properties/shorthand/position.mako.rs
index 667462f6b05..6a4661c4f56 100644
--- a/components/style/properties/shorthand/position.mako.rs
+++ b/components/style/properties/shorthand/position.mako.rs
@@ -147,7 +147,7 @@
         let end = if input.try(|i| i.expect_delim('/')).is_ok() {
             GridLine::parse(context, input)?
         } else {
-            let mut line = GridLine::default();
+            let mut line = GridLine::auto();
             if start.line_num.is_none() && !start.is_span {
                 line.ident = start.ident.clone();       // ident from start value should be taken
             }
@@ -182,7 +182,7 @@
     pub fn parse_value<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>)
                                -> Result<Longhands, ParseError<'i>> {
         fn line_with_ident_from(other: &GridLine) -> GridLine {
-            let mut this = GridLine::default();
+            let mut this = GridLine::auto();
             if other.line_num.is_none() && !other.is_span {
                 this.ident = other.ident.clone();
             }
diff --git a/components/style/values/computed/mod.rs b/components/style/values/computed/mod.rs
index a1ca7b8422b..304fee4bba9 100644
--- a/components/style/values/computed/mod.rs
+++ b/components/style/values/computed/mod.rs
@@ -21,9 +21,9 @@ use std::sync::Arc;
 use style_traits::ToCss;
 use super::{CSSFloat, CSSInteger};
 use super::generics::{GreaterThanOrEqualToOne, NonNegative};
-use super::generics::grid::{TrackBreadth as GenericTrackBreadth, TrackSize as GenericTrackSize};
+use super::generics::grid::{GridLine as GenericGridLine, TrackBreadth as GenericTrackBreadth};
+use super::generics::grid::{TrackSize as GenericTrackSize, TrackList as GenericTrackList};
 use super::generics::grid::GridTemplateComponent as GenericGridTemplateComponent;
-use super::generics::grid::TrackList as GenericTrackList;
 use super::specified;
 
 pub use app_units::Au;
@@ -44,7 +44,6 @@ pub use self::gecko::ScrollSnapPoint;
 pub use self::rect::LengthOrNumberRect;
 pub use super::{Auto, Either, None_};
 pub use super::specified::BorderStyle;
-pub use super::generics::grid::GridLine;
 pub use self::length::{CalcLengthOrPercentage, Length, LengthOrNone, LengthOrNumber, LengthOrPercentage};
 pub use self::length::{LengthOrPercentageOrAuto, LengthOrPercentageOrNone, MaxLength, MozLength};
 pub use self::length::NonNegativeLengthOrPercentage;
@@ -502,10 +501,13 @@ pub type TrackSize = GenericTrackSize<LengthOrPercentage>;
 
 /// The computed value of a grid `<track-list>`
 /// (could also be `<auto-track-list>` or `<explicit-track-list>`)
-pub type TrackList = GenericTrackList<LengthOrPercentage>;
+pub type TrackList = GenericTrackList<LengthOrPercentage, Integer>;
+
+/// The computed value of a `<grid-line>`.
+pub type GridLine = GenericGridLine<Integer>;
 
 /// `<grid-template-rows> | <grid-template-columns>`
-pub type GridTemplateComponent = GenericGridTemplateComponent<LengthOrPercentage>;
+pub type GridTemplateComponent = GenericGridTemplateComponent<LengthOrPercentage, Integer>;
 
 impl ClipRectOrAuto {
     /// Return an auto (default for clip-rect and image-region) value
diff --git a/components/style/values/generics/grid.rs b/components/style/values/generics/grid.rs
index a70c0e7c4c3..5a05b318733 100644
--- a/components/style/values/generics/grid.rs
+++ b/components/style/values/generics/grid.rs
@@ -11,15 +11,15 @@ use std::{fmt, mem, usize};
 use style_traits::{ToCss, ParseError, StyleParseError};
 use values::{CSSFloat, CustomIdent, serialize_dimension};
 use values::computed::{ComputedValueAsSpecified, Context, ToComputedValue};
-use values::specified::Integer;
+use values::specified;
 use values::specified::grid::parse_line_names;
 
-#[derive(Clone, Debug, PartialEq)]
+#[derive(Clone, Debug, Default, PartialEq, ToComputedValue)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 /// A `<grid-line>` type.
 ///
 /// https://drafts.csswg.org/css-grid/#typedef-grid-row-start-grid-line
-pub struct GridLine {
+pub struct GridLine<Integer> {
     /// Flag to check whether it's a `span` keyword.
     pub is_span: bool,
     /// A custom identifier for named lines.
@@ -30,24 +30,26 @@ pub struct GridLine {
     pub line_num: Option<Integer>,
 }
 
-impl GridLine {
+impl<Integer> GridLine<Integer> {
+    /// The `auto` value.
+    pub fn auto() -> Self {
+        Self {
+            is_span: false,
+            line_num: None,
+            ident: None,
+        }
+    }
+
     /// Check whether this `<grid-line>` represents an `auto` value.
     pub fn is_auto(&self) -> bool {
         self.ident.is_none() && self.line_num.is_none() && !self.is_span
     }
 }
 
-impl Default for GridLine {
-    fn default() -> Self {
-        GridLine {
-            is_span: false,
-            ident: None,
-            line_num: None,
-        }
-    }
-}
-
-impl ToCss for GridLine {
+impl<Integer> ToCss for GridLine<Integer>
+where
+    Integer: ToCss,
+{
     fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
         if self.is_auto() {
             return dest.write_str("auto")
@@ -57,9 +59,9 @@ impl ToCss for GridLine {
             dest.write_str("span")?;
         }
 
-        if let Some(i) = self.line_num {
+        if let Some(ref i) = self.line_num {
             dest.write_str(" ")?;
-            i.value().to_css(dest)?;
+            i.to_css(dest)?;
         }
 
         if let Some(ref s) = self.ident {
@@ -71,9 +73,9 @@ impl ToCss for GridLine {
     }
 }
 
-impl Parse for GridLine {
+impl Parse for GridLine<specified::Integer> {
     fn parse<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
-        let mut grid_line = Default::default();
+        let mut grid_line = Self::auto();
         if input.try(|i| i.expect_ident_matching("auto")).is_ok() {
             return Ok(grid_line)
         }
@@ -95,7 +97,8 @@ impl Parse for GridLine {
                 }
 
                 grid_line.is_span = true;
-            } else if let Ok(i) = input.try(|i| Integer::parse(context, i)) {
+            } else if let Ok(i) = input.try(|i| specified::Integer::parse(context, i)) {
+                // FIXME(emilio): Probably shouldn't reject if it's calc()...
                 if i.value() == 0 || val_before_span || grid_line.line_num.is_some() {
                     return Err(StyleParseError::UnspecifiedError.into())
                 }
@@ -129,8 +132,6 @@ impl Parse for GridLine {
     }
 }
 
-impl ComputedValueAsSpecified for GridLine {}
-
 define_css_keyword_enum!{ TrackKeyword:
     "auto" => Auto,
     "max-content" => MaxContent,
@@ -316,9 +317,15 @@ impl<L: ToComputedValue> ToComputedValue for TrackSize<L> {
 
 /// Helper function for serializing identifiers with a prefix and suffix, used
 /// for serializing <line-names> (in grid).
-pub fn concat_serialize_idents<W>(prefix: &str, suffix: &str,
-                                  slice: &[CustomIdent], sep: &str, dest: &mut W) -> fmt::Result
-    where W: fmt::Write
+pub fn concat_serialize_idents<W>(
+    prefix: &str,
+    suffix: &str,
+    slice: &[CustomIdent],
+    sep: &str,
+    dest: &mut W,
+) -> fmt::Result
+where
+    W: fmt::Write
 {
     if let Some((ref first, rest)) = slice.split_first() {
         dest.write_str(prefix)?;
@@ -338,8 +345,8 @@ pub fn concat_serialize_idents<W>(prefix: &str, suffix: &str,
 ///
 /// https://drafts.csswg.org/css-grid/#typedef-track-repeat
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
-#[derive(Clone, Copy, Debug, PartialEq, ToCss)]
-pub enum RepeatCount {
+#[derive(Clone, Copy, Debug, PartialEq, ToComputedValue, ToCss)]
+pub enum RepeatCount<Integer> {
     /// A positive integer. This is allowed only for `<track-repeat>` and `<fixed-repeat>`
     Number(Integer),
     /// An `<auto-fill>` keyword allowed only for `<auto-repeat>`
@@ -348,19 +355,15 @@ pub enum RepeatCount {
     AutoFit,
 }
 
-impl Parse for RepeatCount {
+impl Parse for RepeatCount<specified::Integer> {
     fn parse<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
         // Maximum number of repeat is 10000. The greater numbers should be clamped.
         const MAX_LINE: i32 = 10000;
-        if let Ok(mut i) = input.try(|i| Integer::parse(context, i)) {
-            if i.value() > 0 {
-                if i.value() > MAX_LINE {
-                    i = Integer::new(MAX_LINE);
-                }
-                Ok(RepeatCount::Number(i))
-            } else {
-                Err(StyleParseError::UnspecifiedError.into())
+        if let Ok(mut i) = input.try(|i| specified::Integer::parse_positive(context, i)) {
+            if i.value() > MAX_LINE {
+                i = specified::Integer::new(MAX_LINE);
             }
+            Ok(RepeatCount::Number(i))
         } else {
             try_match_ident_ignore_ascii_case! { input.expect_ident()?,
                 "auto-fill" => Ok(RepeatCount::AutoFill),
@@ -370,17 +373,15 @@ impl Parse for RepeatCount {
     }
 }
 
-impl ComputedValueAsSpecified for RepeatCount {}
-
 /// The structure containing `<line-names>` and `<track-size>` values.
 ///
 /// It can also hold `repeat()` function parameters, which expands into the respective
 /// values in its computed form.
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 #[derive(Clone, Debug, PartialEq, ToComputedValue)]
-pub struct TrackRepeat<L> {
+pub struct TrackRepeat<L, I> {
     /// The number of times for the value to be repeated (could also be `auto-fit` or `auto-fill`)
-    pub count: RepeatCount,
+    pub count: RepeatCount<I>,
     /// `<line-names>` accompanying `<track_size>` values.
     ///
     /// If there's no `<line-names>`, then it's represented by an empty vector.
@@ -392,7 +393,7 @@ pub struct TrackRepeat<L> {
     pub track_sizes: Vec<TrackSize<L>>,
 }
 
-impl<L: ToCss> ToCss for TrackRepeat<L> {
+impl<L: ToCss, I: ToCss> ToCss for TrackRepeat<L, I> {
     fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
         dest.write_str("repeat(")?;
         self.count.to_css(dest)?;
@@ -418,7 +419,7 @@ impl<L: ToCss> ToCss for TrackRepeat<L> {
         Ok(())
     }
 }
-impl<L: Clone> TrackRepeat<L> {
+impl<L: Clone> TrackRepeat<L, specified::Integer> {
     /// If the repeat count is numeric, then expand the values and merge accordingly.
     pub fn expand(&self) -> Self {
         if let RepeatCount::Number(num) = self.count {
@@ -460,11 +461,11 @@ impl<L: Clone> TrackRepeat<L> {
 /// Track list values. Can be <track-size> or <track-repeat>
 #[derive(Clone, Debug, PartialEq, ToComputedValue, ToCss)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
-pub enum TrackListValue<T> {
+pub enum TrackListValue<LengthOrPercentage, Integer> {
     /// A <track-size> value.
-    TrackSize(TrackSize<T>),
+    TrackSize(TrackSize<LengthOrPercentage>),
     /// A <track-repeat> value.
-    TrackRepeat(TrackRepeat<T>),
+    TrackRepeat(TrackRepeat<LengthOrPercentage, Integer>),
 }
 
 /// The type of a `<track-list>` as determined during parsing.
@@ -497,14 +498,14 @@ impl ComputedValueAsSpecified for TrackListType {}
 /// https://drafts.csswg.org/css-grid/#typedef-track-list
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 #[derive(Clone, Debug, PartialEq)]
-pub struct TrackList<T> {
+pub struct TrackList<LengthOrPercentage, Integer> {
     /// The type of this `<track-list>` (auto, explicit or general).
     ///
     /// In order to avoid parsing the same value multiple times, this does a single traversal
     /// and arrives at the type of value it has parsed (or bails out gracefully with an error).
     pub list_type: TrackListType,
     /// A vector of `<track-size> | <track-repeat>` values.
-    pub values: Vec<TrackListValue<T>>,
+    pub values: Vec<TrackListValue<LengthOrPercentage, Integer>>,
     /// `<line-names>` accompanying `<track-size> | <track-repeat>` values.
     ///
     /// If there's no `<line-names>`, then it's represented by an empty vector.
@@ -512,10 +513,10 @@ pub struct TrackList<T> {
     /// length is always one value more than that of the `<track-size>`.
     pub line_names: Box<[Box<[CustomIdent]>]>,
     /// `<auto-repeat>` value. There can only be one `<auto-repeat>` in a TrackList.
-    pub auto_repeat: Option<TrackRepeat<T>>,
+    pub auto_repeat: Option<TrackRepeat<LengthOrPercentage, Integer>>,
 }
 
-impl<T: ToCss> ToCss for TrackList<T> {
+impl<L: ToCss, I: ToCss> ToCss for TrackList<L, I> {
     fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
         let auto_idx = match self.list_type {
             TrackListType::Auto(i) => i as usize,
@@ -661,16 +662,16 @@ impl ComputedValueAsSpecified for LineNameList {}
 /// But it's implemented in gecko, so we have to as well.
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 #[derive(Clone, Debug, PartialEq, ToComputedValue, ToCss)]
-pub enum GridTemplateComponent<L> {
+pub enum GridTemplateComponent<L, I> {
     /// `none` value.
     None,
     /// The grid `<track-list>`
-    TrackList(TrackList<L>),
+    TrackList(TrackList<L, I>),
     /// A `subgrid <line-name-list>?`
     Subgrid(LineNameList),
 }
 
-impl<L> GridTemplateComponent<L> {
+impl<L, I> GridTemplateComponent<L, I> {
     /// Returns length of the <track-list>s <track-size>
     pub fn track_list_len(&self) -> usize {
         match *self {
diff --git a/components/style/values/specified/grid.rs b/components/style/values/specified/grid.rs
index f68325f9c27..72e6ebec5d8 100644
--- a/components/style/values/specified/grid.rs
+++ b/components/style/values/specified/grid.rs
@@ -14,7 +14,7 @@ use values::{CSSFloat, CustomIdent};
 use values::computed::{self, Context, ToComputedValue};
 use values::generics::grid::{GridTemplateComponent, RepeatCount, TrackBreadth, TrackKeyword, TrackRepeat};
 use values::generics::grid::{LineNameList, TrackSize, TrackList, TrackListType, TrackListValue};
-use values::specified::LengthOrPercentage;
+use values::specified::{LengthOrPercentage, Integer};
 
 /// Parse a single flexible length.
 pub fn parse_flex<'i, 't>(input: &mut Parser<'i, 't>) -> Result<CSSFloat, ParseError<'i>> {
@@ -97,9 +97,11 @@ enum RepeatType {
     Fixed,
 }
 
-impl TrackRepeat<LengthOrPercentage> {
-    fn parse_with_repeat_type<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>)
-                                      -> Result<(TrackRepeat<LengthOrPercentage>, RepeatType), ParseError<'i>> {
+impl TrackRepeat<LengthOrPercentage, Integer> {
+    fn parse_with_repeat_type<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<(Self, RepeatType), ParseError<'i>> {
         input.try(|i| i.expect_function_matching("repeat").map_err(|e| e.into())).and_then(|_| {
             input.parse_nested_block(|input| {
                 let count = RepeatCount::parse(context, input)?;
@@ -165,7 +167,7 @@ impl TrackRepeat<LengthOrPercentage> {
     }
 }
 
-impl Parse for TrackList<LengthOrPercentage> {
+impl Parse for TrackList<LengthOrPercentage, Integer> {
     fn parse<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
         let mut current_names = vec![];
         let mut names = vec![];
@@ -248,8 +250,8 @@ impl Parse for TrackList<LengthOrPercentage> {
     }
 }
 
-impl ToComputedValue for TrackList<LengthOrPercentage> {
-    type ComputedValue = TrackList<computed::LengthOrPercentage>;
+impl ToComputedValue for TrackList<LengthOrPercentage, Integer> {
+    type ComputedValue = TrackList<computed::LengthOrPercentage, computed::Integer>;
 
     #[inline]
     fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
@@ -321,7 +323,7 @@ impl ToComputedValue for TrackList<LengthOrPercentage> {
     }
 }
 
-impl Parse for GridTemplateComponent<LengthOrPercentage> {
+impl Parse for GridTemplateComponent<LengthOrPercentage, Integer> {
     // FIXME: Derive Parse (probably with None_)
     fn parse<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
         if input.try(|i| i.expect_ident_matching("none")).is_ok() {
@@ -332,10 +334,12 @@ impl Parse for GridTemplateComponent<LengthOrPercentage> {
     }
 }
 
-impl GridTemplateComponent<LengthOrPercentage> {
+impl GridTemplateComponent<LengthOrPercentage, Integer> {
     /// Parses a `GridTemplateComponent<LengthOrPercentage>` except `none` keyword.
-    pub fn parse_without_none<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>)
-                                      -> Result<Self, ParseError<'i>> {
+    pub fn parse_without_none<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
         if let Ok(t) = input.try(|i| TrackList::parse(context, i)) {
             return Ok(GridTemplateComponent::TrackList(t))
         }
diff --git a/components/style/values/specified/mod.rs b/components/style/values/specified/mod.rs
index ecceede0156..7c91096bb8b 100644
--- a/components/style/values/specified/mod.rs
+++ b/components/style/values/specified/mod.rs
@@ -19,8 +19,8 @@ use style_traits::values::specified::AllowedNumericType;
 use super::{Auto, CSSFloat, CSSInteger, Either, None_};
 use super::computed::{Context, ToComputedValue};
 use super::generics::{GreaterThanOrEqualToOne, NonNegative};
-use super::generics::grid::{TrackBreadth as GenericTrackBreadth, TrackSize as GenericTrackSize};
-use super::generics::grid::TrackList as GenericTrackList;
+use super::generics::grid::{GridLine as GenericGridLine, TrackBreadth as GenericTrackBreadth};
+use super::generics::grid::{TrackSize as GenericTrackSize, TrackList as GenericTrackList};
 use values::computed::ComputedValueAsSpecified;
 use values::specified::calc::CalcNode;
 
@@ -52,7 +52,6 @@ pub use self::svg::{SVGLength, SVGOpacity, SVGPaint, SVGPaintKind, SVGStrokeDash
 pub use self::text::{InitialLetter, LetterSpacing, LineHeight, WordSpacing};
 pub use self::time::Time;
 pub use self::transform::{TimingFunction, TransformOrigin};
-pub use super::generics::grid::GridLine;
 pub use super::generics::grid::GridTemplateComponent as GenericGridTemplateComponent;
 
 #[cfg(feature = "gecko")]
@@ -356,9 +355,11 @@ impl ToComputedValue for Opacity {
     }
 }
 
+/// An specified `<integer>`, optionally coming from a `calc()` expression.
+///
+/// https://drafts.csswg.org/css-values/#integers
 #[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
-#[allow(missing_docs)]
 pub struct Integer {
     value: CSSInteger,
     was_calc: bool,
@@ -387,7 +388,6 @@ impl Integer {
     }
 }
 
-
 impl Parse for Integer {
     fn parse<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
         parse_integer(context, input)
@@ -395,25 +395,37 @@ impl Parse for Integer {
 }
 
 impl Integer {
-    #[allow(missing_docs)]
-    pub fn parse_with_minimum<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>, min: i32)
-                                      -> Result<Integer, ParseError<'i>> {
+    /// Parse an integer value which is at least `min`.
+    pub fn parse_with_minimum<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        min: i32
+    ) -> Result<Integer, ParseError<'i>> {
         match parse_integer(context, input) {
+            // FIXME(emilio): The spec asks us to avoid rejecting it at parse
+            // time except until computed value time.
+            //
+            // It's not totally clear it's worth it though, and no other browser
+            // does this.
             Ok(value) if value.value() >= min => Ok(value),
             Ok(_value) => Err(StyleParseError::UnspecifiedError.into()),
             Err(e) => Err(e),
         }
     }
 
-    #[allow(missing_docs)]
-    pub fn parse_non_negative<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>)
-                                      -> Result<Integer, ParseError<'i>> {
+    /// Parse a non-negative integer.
+    pub fn parse_non_negative<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Integer, ParseError<'i>> {
         Integer::parse_with_minimum(context, input, 0)
     }
 
-    #[allow(missing_docs)]
-    pub fn parse_positive<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>)
-                                  -> Result<Integer, ParseError<'i>> {
+    /// Parse a positive integer (>= 1).
+    pub fn parse_positive<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>
+    ) -> Result<Integer, ParseError<'i>> {
         Integer::parse_with_minimum(context, input, 1)
     }
 }
@@ -484,10 +496,13 @@ pub type TrackSize = GenericTrackSize<LengthOrPercentage>;
 
 /// The specified value of a grid `<track-list>`
 /// (could also be `<auto-track-list>` or `<explicit-track-list>`)
-pub type TrackList = GenericTrackList<LengthOrPercentage>;
+pub type TrackList = GenericTrackList<LengthOrPercentage, Integer>;
+
+/// The specified value of a `<grid-line>`.
+pub type GridLine = GenericGridLine<Integer>;
 
 /// `<grid-template-rows> | <grid-template-columns>`
-pub type GridTemplateComponent = GenericGridTemplateComponent<LengthOrPercentage>;
+pub type GridTemplateComponent = GenericGridTemplateComponent<LengthOrPercentage, Integer>;
 
 /// <length> | <percentage> | <number>
 pub type LengthOrPercentageOrNumber = Either<Number, LengthOrPercentage>;