feat: implement requires directives

naga/src/front/wgsl/error.rs

@@ -1,6 +1,9 @@
 use crate::front::wgsl::parse::directive::enable_extension::{
     EnableExtension, UnimplementedEnableExtension,
 };
+use crate::front::wgsl::parse::directive::language_extension::{
+    LanguageExtension, UnimplementedLanguageExtension,
+};
 use crate::front::wgsl::parse::directive::{DirectiveKind, UnimplementedDirectiveKind};
 use crate::front::wgsl::parse::lexer::Token;
 use crate::front::wgsl::Scalar;
@@ -190,6 +193,7 @@ pub(crate) enum Error<'a> {
     UnknownStorageFormat(Span),
     UnknownConservativeDepth(Span),
     UnknownEnableExtension(Span, &'a str),
+    UnknownLanguageExtension(Span, &'a str),
     SizeAttributeTooLow(Span, u32),
     AlignAttributeTooLow(Span, Alignment),
     NonPowerOfTwoAlignAttribute(Span),
@@ -287,6 +291,10 @@ pub(crate) enum Error<'a> {
         kind: EnableExtension,
         span: Span,
     },
+    LanguageExtensionNotYetImplemented {
+        kind: UnimplementedLanguageExtension,
+        span: Span,
+    },
 }
 
 #[derive(Clone, Debug)]
@@ -545,6 +553,15 @@ impl<'a> Error<'a> {
                         .into(),
                 ],
             },
+            Error::UnknownLanguageExtension(span, name) => ParseError {
+                message: format!("unknown language extension `{name}`"),
+                labels: vec![(span, "".into())],
+                notes: vec![concat!(
+                    "See available extensions at ",
+                    "<https://www.w3.org/TR/WGSL/#language-extensions-sec>."
+                )
+                .into()],
+            },
             Error::SizeAttributeTooLow(bad_span, min_size) => ParseError {
                 message: format!("struct member size must be at least {min_size}"),
                 labels: vec![(bad_span, format!("must be at least {min_size}").into())],
@@ -976,6 +993,21 @@ impl<'a> Error<'a> {
                     vec![]
                 },
             },
+            Error::LanguageExtensionNotYetImplemented { kind, span } => ParseError {
+                message: format!(
+                    "the `{}` language extension is not yet supported",
+                    LanguageExtension::Unimplemented(kind).to_ident()
+                ),
+                labels: vec![(span, "".into())],
+                notes: vec![format!(
+                    concat!(
+                        "Let Naga maintainers know that you ran into this at ",
+                        "<https://github.com/gfx-rs/wgpu/issues/{}>, ",
+                        "so they can prioritize it!"
+                    ),
+                    kind.tracking_issue_num()
+                )],
+            },
         }
     }
 }

naga/src/front/wgsl/parse/directive.rs

@@ -3,12 +3,14 @@
 //! See also <https://www.w3.org/TR/WGSL/#directives>.
 
 pub mod enable_extension;
+pub(crate) mod language_extension;
 
 /// A parsed sentinel word indicating the type of directive to be parsed next.
 #[derive(Clone, Copy, Debug, Hash, Eq, PartialEq)]
 pub enum DirectiveKind {
     /// An [`enable_extension`].
     Enable,
+    Requires,
     Unimplemented(UnimplementedDirectiveKind),
 }
 
@@ -22,7 +24,7 @@ impl DirectiveKind {
         Some(match s {
             Self::DIAGNOSTIC => Self::Unimplemented(UnimplementedDirectiveKind::Diagnostic),
             Self::ENABLE => Self::Enable,
-            Self::REQUIRES => Self::Unimplemented(UnimplementedDirectiveKind::Requires),
+            Self::REQUIRES => Self::Requires,
             _ => return None,
         })
     }
@@ -31,9 +33,9 @@ impl DirectiveKind {
     pub const fn to_ident(self) -> &'static str {
         match self {
             Self::Enable => Self::ENABLE,
+            Self::Requires => Self::REQUIRES,
             Self::Unimplemented(kind) => match kind {
                 UnimplementedDirectiveKind::Diagnostic => Self::DIAGNOSTIC,
-                UnimplementedDirectiveKind::Requires => Self::REQUIRES,
             },
         }
     }
@@ -51,14 +53,12 @@ impl DirectiveKind {
 #[cfg_attr(test, derive(strum::EnumIter))]
 pub enum UnimplementedDirectiveKind {
     Diagnostic,
-    Requires,
 }
 
 impl UnimplementedDirectiveKind {
     pub const fn tracking_issue_num(self) -> u16 {
         match self {
             Self::Diagnostic => 5320,
-            Self::Requires => 6350,
         }
     }
 }
@@ -88,19 +88,6 @@ error: `diagnostic` is not yet implemented
   │
   = note: Let Naga maintainers know that you ran into this at <https://github.com/gfx-rs/wgpu/issues/5320>, so they can prioritize it!
 
-";
-                }
-                UnimplementedDirectiveKind::Requires => {
-                    shader = "requires readonly_and_readwrite_storage_textures";
-                    expected_msg = "\
-error: `requires` is not yet implemented
-  ┌─ wgsl:1:1
-  │
-1 │ requires readonly_and_readwrite_storage_textures
-  │ ^^^^^^^^ this global directive is standard, but not yet implemented
-  │
-  = note: Let Naga maintainers know that you ran into this at <https://github.com/gfx-rs/wgpu/issues/6350>, so they can prioritize it!
-
 ";
                 }
             };
@@ -141,7 +128,7 @@ error: expected global declaration, but found a global directive
 
 ";
                 }
-                DirectiveKind::Unimplemented(UnimplementedDirectiveKind::Requires) => {
+                DirectiveKind::Requires => {
                     directive = "requires readonly_and_readwrite_storage_textures";
                     expected_msg = "\
 error: expected global declaration, but found a global directive

naga/src/front/wgsl/parse/directive/language_extension.rs

@@ -0,0 +1,85 @@
+//! `requires …;` extensions in WGSL.
+//!
+//! The focal point of this module is the [`LanguageExtension`] API.
+
+/// A shader language extension not guaranteed to be present in all environments.
+///
+/// WGSL spec.: <https://www.w3.org/TR/WGSL/#language-extensions-sec>
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+pub(crate) enum LanguageExtension {
+    #[allow(unused)]
+    Implemented(ImplementedLanguageExtension),
+    Unimplemented(UnimplementedLanguageExtension),
+}
+
+impl LanguageExtension {
+    const READONLY_AND_READWRITE_STORAGE_TEXTURES: &'static str =
+        "readonly_and_readwrite_storage_textures";
+    const PACKED4X8_INTEGER_DOT_PRODUCT: &'static str = "packed_4x8_integer_dot_product";
+    const UNRESTRICTED_POINTER_PARAMETERS: &'static str = "unrestricted_pointer_parameters";
+    const POINTER_COMPOSITE_ACCESS: &'static str = "pointer_composite_access";
+
+    /// Convert from a sentinel word in WGSL into its associated [`LanguageExtension`], if possible.
+    pub fn from_ident(s: &str) -> Option<Self> {
+        Some(match s {
+            Self::READONLY_AND_READWRITE_STORAGE_TEXTURES => Self::Unimplemented(
+                UnimplementedLanguageExtension::ReadOnlyAndReadWriteStorageTextures,
+            ),
+            Self::PACKED4X8_INTEGER_DOT_PRODUCT => {
+                Self::Unimplemented(UnimplementedLanguageExtension::Packed4x8IntegerDotProduct)
+            }
+            Self::UNRESTRICTED_POINTER_PARAMETERS => {
+                Self::Unimplemented(UnimplementedLanguageExtension::UnrestrictedPointerParameters)
+            }
+            Self::POINTER_COMPOSITE_ACCESS => {
+                Self::Unimplemented(UnimplementedLanguageExtension::PointerCompositeAccess)
+            }
+            _ => return None,
+        })
+    }
+
+    /// Maps this [`LanguageExtension`] into the sentinel word associated with it in WGSL.
+    pub fn to_ident(self) -> &'static str {
+        match self {
+            Self::Implemented(kind) => match kind {},
+            Self::Unimplemented(kind) => match kind {
+                UnimplementedLanguageExtension::ReadOnlyAndReadWriteStorageTextures => {
+                    Self::READONLY_AND_READWRITE_STORAGE_TEXTURES
+                }
+                UnimplementedLanguageExtension::Packed4x8IntegerDotProduct => {
+                    Self::PACKED4X8_INTEGER_DOT_PRODUCT
+                }
+                UnimplementedLanguageExtension::UnrestrictedPointerParameters => {
+                    Self::UNRESTRICTED_POINTER_PARAMETERS
+                }
+                UnimplementedLanguageExtension::PointerCompositeAccess => {
+                    Self::POINTER_COMPOSITE_ACCESS
+                }
+            },
+        }
+    }
+}
+
+/// A variant of [`LanguageExtension::Implemented`].
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+pub(crate) enum ImplementedLanguageExtension {}
+
+/// A variant of [`LanguageExtension::Unimplemented`].
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+pub(crate) enum UnimplementedLanguageExtension {
+    ReadOnlyAndReadWriteStorageTextures,
+    Packed4x8IntegerDotProduct,
+    UnrestrictedPointerParameters,
+    PointerCompositeAccess,
+}
+
+impl UnimplementedLanguageExtension {
+    pub(crate) fn tracking_issue_num(self) -> u16 {
+        match self {
+            Self::ReadOnlyAndReadWriteStorageTextures => 6204,
+            Self::Packed4x8IntegerDotProduct => 6445,
+            Self::UnrestrictedPointerParameters => 5158,
+            Self::PointerCompositeAccess => 6192,
+        }
+    }
+}

naga/src/front/wgsl/parse/mod.rs

@@ -2,6 +2,7 @@ use crate::front::wgsl::error::{Error, ExpectedToken};
 use crate::front::wgsl::parse::directive::enable_extension::{
     EnableExtension, EnableExtensions, UnimplementedEnableExtension,
 };
+use crate::front::wgsl::parse::directive::language_extension::LanguageExtension;
 use crate::front::wgsl::parse::directive::DirectiveKind;
 use crate::front::wgsl::parse::lexer::{Lexer, Token};
 use crate::front::wgsl::parse::number::Number;
@@ -2544,6 +2545,23 @@ impl Parser {
                             Ok(())
                         })?;
                     }
+                    DirectiveKind::Requires => {
+                        self.directive_ident_list(&mut lexer, |ident, span| {
+                            match LanguageExtension::from_ident(ident) {
+                                Some(LanguageExtension::Implemented(_kind)) => {
+                                    // NOTE: No further validation is needed for an extension, so
+                                    // just throw parsed information away. If we ever want to apply
+                                    // what we've parsed to diagnostics, maybe we'll want to refer
+                                    // to enabled extensions later?
+                                    Ok(())
+                                }
+                                Some(LanguageExtension::Unimplemented(kind)) => {
+                                    Err(Error::LanguageExtensionNotYetImplemented { kind, span })
+                                }
+                                None => Err(Error::UnknownLanguageExtension(span, ident)),
+                            }
+                        })?;
+                    }
                     DirectiveKind::Unimplemented(kind) => {
                         return Err(Error::DirectiveNotYetImplemented { kind, span })
                     }