intrinsic_table.def: Support [[deprecated]] on fn

And produce a warning if these are used. Hard to test, as we don't want to introduce fake functions in our definition file.

Also add missing cast in EnumMatcher.

Bug: tint:806
Change-Id: I21f189e4befe419f6d5544acfc52387d9a5da782
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/54001
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: David Neto <dneto@google.com>

tools/src/cmd/intrinsic-gen/gen/intrinsic_table.go

@@ -98,6 +98,8 @@ type Overload struct {
 	ReturnMatcherIndicesOffset *int
 	// StageUses describes the stages an overload can be used in
 	CanBeUsedInStage sem.StageUses
+	// True if the overload is marked as deprecated
+	IsDeprecated bool
 }
 
 // Function is used to create the C++ IntrinsicInfo structure
@@ -196,6 +198,7 @@ func (b *intrinsicTableBuilder) buildOverload(o *sem.Overload) (Overload, error)
 		ParametersOffset:           b.lut.parameters.Add(ob.parameters),
 		ReturnMatcherIndicesOffset: ob.returnTypeMatcherIndicesOffset,
 		CanBeUsedInStage:           o.CanBeUsedInStage,
+		IsDeprecated:               o.IsDeprecated,
 	}, nil
 }
 

tools/src/cmd/intrinsic-gen/resolver/resolve.go

@@ -275,6 +275,12 @@ func (r *resolver) function(a ast.FunctionDecl) error {
 			Compute:  true,
 		}
 	}
+	if deprecated := a.Decorations.Take("deprecated"); deprecated != nil {
+		overload.IsDeprecated = true
+		if len(deprecated.Values) != 0 {
+			return fmt.Errorf("%v unexpected value for deprecated decoration", deprecated.Source)
+		}
+	}
 	if len(a.Decorations) != 0 {
 		return fmt.Errorf("%v unknown decoration", a.Decorations[0].Source)
 	}

tools/src/cmd/intrinsic-gen/sem/sem.go

@@ -137,6 +137,7 @@ type Overload struct {
 	ReturnType       *FullyQualifiedName
 	Parameters       []Parameter
 	CanBeUsedInStage StageUses
+	IsDeprecated     bool // True if this overload is deprecated
 }
 
 // StageUses describes the stages an overload can be used in