[naga wgsl] Move diagnostics definitions into their own module.

In `naga::common::wgsl`, move `DisplayFilterableTriggeringRule` and
diagnostics-related impls into a new sub-module, `diagonostics`.

This change is only code motion; there should be no change in
behavior.

naga/src/common/wgsl/diagnostics.rs

@@ -0,0 +1,69 @@
+//! WGSL diagnostic filters and severities.
+
+use core::fmt::{self, Display, Formatter};
+
+use crate::diagnostic_filter::{
+    FilterableTriggeringRule, Severity, StandardFilterableTriggeringRule,
+};
+
+impl Severity {
+    const ERROR: &'static str = "error";
+    const WARNING: &'static str = "warning";
+    const INFO: &'static str = "info";
+    const OFF: &'static str = "off";
+
+    /// Convert from a sentinel word in WGSL into its associated [`Severity`], if possible.
+    pub fn from_wgsl_ident(s: &str) -> Option<Self> {
+        Some(match s {
+            Self::ERROR => Self::Error,
+            Self::WARNING => Self::Warning,
+            Self::INFO => Self::Info,
+            Self::OFF => Self::Off,
+            _ => return None,
+        })
+    }
+}
+
+pub struct DisplayFilterableTriggeringRule<'a>(&'a FilterableTriggeringRule);
+
+impl Display for DisplayFilterableTriggeringRule<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        let &Self(inner) = self;
+        match *inner {
+            FilterableTriggeringRule::Standard(rule) => write!(f, "{}", rule.to_wgsl_ident()),
+            FilterableTriggeringRule::Unknown(ref rule) => write!(f, "{rule}"),
+            FilterableTriggeringRule::User(ref rules) => {
+                let &[ref seg1, ref seg2] = rules.as_ref();
+                write!(f, "{seg1}.{seg2}")
+            }
+        }
+    }
+}
+
+impl FilterableTriggeringRule {
+    /// [`Display`] this rule's identifiers in WGSL.
+    pub const fn display_wgsl_ident(&self) -> impl Display + '_ {
+        DisplayFilterableTriggeringRule(self)
+    }
+}
+
+impl StandardFilterableTriggeringRule {
+    const DERIVATIVE_UNIFORMITY: &'static str = "derivative_uniformity";
+
+    /// Convert from a sentinel word in WGSL into its associated
+    /// [`StandardFilterableTriggeringRule`], if possible.
+    pub fn from_wgsl_ident(s: &str) -> Option<Self> {
+        Some(match s {
+            Self::DERIVATIVE_UNIFORMITY => Self::DerivativeUniformity,
+            _ => return None,
+        })
+    }
+
+    /// Maps this [`StandardFilterableTriggeringRule`] into the sentinel word associated with it in
+    /// WGSL.
+    pub const fn to_wgsl_ident(self) -> &'static str {
+        match self {
+            Self::DerivativeUniformity => Self::DERIVATIVE_UNIFORMITY,
+        }
+    }
+}

naga/src/common/wgsl/mod.rs

@@ -1,77 +1,11 @@
 //! Code shared between the WGSL front and back ends.
 
+mod diagnostics;
 mod types;
 
-use core::fmt::{self, Display, Formatter};
-
-use crate::diagnostic_filter::{
-    FilterableTriggeringRule, Severity, StandardFilterableTriggeringRule,
-};
-
+pub use diagnostics::DisplayFilterableTriggeringRule;
 pub use types::TypeContext;
 
-impl Severity {
-    const ERROR: &'static str = "error";
-    const WARNING: &'static str = "warning";
-    const INFO: &'static str = "info";
-    const OFF: &'static str = "off";
-
-    /// Convert from a sentinel word in WGSL into its associated [`Severity`], if possible.
-    pub fn from_wgsl_ident(s: &str) -> Option<Self> {
-        Some(match s {
-            Self::ERROR => Self::Error,
-            Self::WARNING => Self::Warning,
-            Self::INFO => Self::Info,
-            Self::OFF => Self::Off,
-            _ => return None,
-        })
-    }
-}
-
-struct DisplayFilterableTriggeringRule<'a>(&'a FilterableTriggeringRule);
-
-impl Display for DisplayFilterableTriggeringRule<'_> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        let &Self(inner) = self;
-        match *inner {
-            FilterableTriggeringRule::Standard(rule) => write!(f, "{}", rule.to_wgsl_ident()),
-            FilterableTriggeringRule::Unknown(ref rule) => write!(f, "{rule}"),
-            FilterableTriggeringRule::User(ref rules) => {
-                let &[ref seg1, ref seg2] = rules.as_ref();
-                write!(f, "{seg1}.{seg2}")
-            }
-        }
-    }
-}
-
-impl FilterableTriggeringRule {
-    /// [`Display`] this rule's identifiers in WGSL.
-    pub const fn display_wgsl_ident(&self) -> impl Display + '_ {
-        DisplayFilterableTriggeringRule(self)
-    }
-}
-
-impl StandardFilterableTriggeringRule {
-    const DERIVATIVE_UNIFORMITY: &'static str = "derivative_uniformity";
-
-    /// Convert from a sentinel word in WGSL into its associated
-    /// [`StandardFilterableTriggeringRule`], if possible.
-    pub fn from_wgsl_ident(s: &str) -> Option<Self> {
-        Some(match s {
-            Self::DERIVATIVE_UNIFORMITY => Self::DerivativeUniformity,
-            _ => return None,
-        })
-    }
-
-    /// Maps this [`StandardFilterableTriggeringRule`] into the sentinel word associated with it in
-    /// WGSL.
-    pub const fn to_wgsl_ident(self) -> &'static str {
-        match self {
-            Self::DerivativeUniformity => Self::DERIVATIVE_UNIFORMITY,
-        }
-    }
-}
-
 /// Types that can return the WGSL source representation of their
 /// values as a `'static` string.
 ///