diff --git a/rust/binary.go b/rust/binary.go
index 860dc94..5e7e922 100644
--- a/rust/binary.go
+++ b/rust/binary.go
@@ -137,12 +137,7 @@
 	fileName := binary.getStem(ctx) + ctx.toolchain().ExecutableSuffix()
 	outputFile := android.PathForModuleOut(ctx, fileName)
 	ret := buildOutput{outputFile: outputFile}
-	var crateRootPath android.Path
-	if binary.baseCompiler.Properties.Crate_root == nil {
-		crateRootPath, _ = srcPathFromModuleSrcs(ctx, binary.baseCompiler.Properties.Srcs)
-	} else {
-		crateRootPath = android.PathForModuleSrc(ctx, *binary.baseCompiler.Properties.Crate_root)
-	}
+	crateRootPath := crateRootPath(ctx, binary)
 
 	flags.RustFlags = append(flags.RustFlags, deps.depFlags...)
 	flags.LinkFlags = append(flags.LinkFlags, deps.depLinkFlags...)
diff --git a/rust/builder.go b/rust/builder.go
index 162d1aa..c855cfb 100644
--- a/rust/builder.go
+++ b/rust/builder.go
@@ -196,7 +196,7 @@
 	}
 
 	if len(deps.SrcDeps) > 0 {
-		moduleGenDir := ctx.RustModule().compiler.CargoOutDir()
+		moduleGenDir := ctx.RustModule().compiler.cargoOutDir()
 		// We must calculate an absolute path for OUT_DIR since Rust's include! macro (which normally consumes this)
 		// assumes that paths are relative to the source file.
 		var outDirPrefix string
@@ -215,13 +215,13 @@
 
 	envVars = append(envVars, "ANDROID_RUST_VERSION="+config.GetRustVersion(ctx))
 
-	if ctx.RustModule().compiler.CargoEnvCompat() {
+	if ctx.RustModule().compiler.cargoEnvCompat() {
 		if bin, ok := ctx.RustModule().compiler.(*binaryDecorator); ok {
 			envVars = append(envVars, "CARGO_BIN_NAME="+bin.getStem(ctx))
 		}
 		envVars = append(envVars, "CARGO_CRATE_NAME="+ctx.RustModule().CrateName())
 		envVars = append(envVars, "CARGO_PKG_NAME="+ctx.RustModule().CrateName())
-		pkgVersion := ctx.RustModule().compiler.CargoPkgVersion()
+		pkgVersion := ctx.RustModule().compiler.cargoPkgVersion()
 		if pkgVersion != "" {
 			envVars = append(envVars, "CARGO_PKG_VERSION="+pkgVersion)
 
@@ -327,7 +327,7 @@
 	orderOnly = append(orderOnly, deps.SharedLibs...)
 
 	if len(deps.SrcDeps) > 0 {
-		moduleGenDir := ctx.RustModule().compiler.CargoOutDir()
+		moduleGenDir := ctx.RustModule().compiler.cargoOutDir()
 		var outputs android.WritablePaths
 
 		for _, genSrc := range deps.SrcDeps {
diff --git a/rust/compiler.go b/rust/compiler.go
index 4c7961d..d453a5d 100644
--- a/rust/compiler.go
+++ b/rust/compiler.go
@@ -16,6 +16,7 @@
 
 import (
 	"android/soong/cc"
+	"errors"
 	"fmt"
 	"path/filepath"
 	"strings"
@@ -34,6 +35,48 @@
 	DylibLinkage
 )
 
+type compiler interface {
+	initialize(ctx ModuleContext)
+	compilerFlags(ctx ModuleContext, flags Flags) Flags
+	cfgFlags(ctx ModuleContext, flags Flags) Flags
+	featureFlags(ctx ModuleContext, flags Flags) Flags
+	compilerProps() []interface{}
+	compile(ctx ModuleContext, flags Flags, deps PathDeps) buildOutput
+	compilerDeps(ctx DepsContext, deps Deps) Deps
+	crateName() string
+	edition() string
+	features() []string
+	rustdoc(ctx ModuleContext, flags Flags, deps PathDeps) android.OptionalPath
+
+	// Output directory in which source-generated code from dependencies is
+	// copied. This is equivalent to Cargo's OUT_DIR variable.
+	cargoOutDir() android.OptionalPath
+
+	// cargoPkgVersion returns the value of the Cargo_pkg_version property.
+	cargoPkgVersion() string
+
+	// cargoEnvCompat returns whether Cargo environment variables should be used.
+	cargoEnvCompat() bool
+
+	inData() bool
+	install(ctx ModuleContext)
+	relativeInstallPath() string
+	everInstallable() bool
+
+	nativeCoverage() bool
+
+	Disabled() bool
+	SetDisabled()
+
+	stdLinkage(ctx *depsContext) RustLinkage
+	noStdlibs() bool
+
+	unstrippedOutputFilePath() android.Path
+	strippedOutputFilePath() android.OptionalPath
+
+	checkedCrateRootPath() (android.Path, error)
+}
+
 func (compiler *baseCompiler) edition() string {
 	return proptools.StringDefault(compiler.Properties.Edition, config.DefaultEdition)
 }
@@ -204,7 +247,16 @@
 
 	// If a crate has a source-generated dependency, a copy of the source file
 	// will be available in cargoOutDir (equivalent to Cargo OUT_DIR).
-	cargoOutDir android.ModuleOutPath
+	// This is stored internally because it may not be available during
+	// singleton-generation passes like rustdoc/rust_project.json, but should
+	// be stashed during initial generation.
+	cachedCargoOutDir android.ModuleOutPath
+	// Calculated crate root cached internally because ModuleContext is not
+	// available to singleton targets like rustdoc/rust_project.json
+	cachedCrateRootPath android.Path
+	// If cachedCrateRootPath is nil after initialization, this will contain
+	// an explanation of why
+	cachedCrateRootError error
 }
 
 func (compiler *baseCompiler) Disabled() bool {
@@ -257,9 +309,13 @@
 	return flags
 }
 
+func (compiler *baseCompiler) features() []string {
+	return compiler.Properties.Features
+}
+
 func (compiler *baseCompiler) featuresToFlags() []string {
 	flags := []string{}
-	for _, feature := range compiler.Properties.Features {
+	for _, feature := range compiler.features() {
 		flags = append(flags, "--cfg 'feature=\""+feature+"\"'")
 	}
 
@@ -355,18 +411,24 @@
 }
 
 func (compiler *baseCompiler) initialize(ctx ModuleContext) {
-	compiler.cargoOutDir = android.PathForModuleOut(ctx, genSubDir)
+	compiler.cachedCargoOutDir = android.PathForModuleOut(ctx, genSubDir)
+	if compiler.Properties.Crate_root == nil {
+		compiler.cachedCrateRootPath, compiler.cachedCrateRootError = srcPathFromModuleSrcs(ctx, compiler.Properties.Srcs)
+	} else {
+		compiler.cachedCrateRootPath = android.PathForModuleSrc(ctx, *compiler.Properties.Crate_root)
+		compiler.cachedCrateRootError = nil
+	}
 }
 
-func (compiler *baseCompiler) CargoOutDir() android.OptionalPath {
-	return android.OptionalPathForPath(compiler.cargoOutDir)
+func (compiler *baseCompiler) cargoOutDir() android.OptionalPath {
+	return android.OptionalPathForPath(compiler.cachedCargoOutDir)
 }
 
-func (compiler *baseCompiler) CargoEnvCompat() bool {
+func (compiler *baseCompiler) cargoEnvCompat() bool {
 	return Bool(compiler.Properties.Cargo_env_compat)
 }
 
-func (compiler *baseCompiler) CargoPkgVersion() string {
+func (compiler *baseCompiler) cargoPkgVersion() string {
 	return String(compiler.Properties.Cargo_pkg_version)
 }
 
@@ -496,12 +558,20 @@
 	return String(compiler.Properties.Relative_install_path)
 }
 
-// Returns the Path for the main source file along with Paths for generated source files from modules listed in srcs.
-func srcPathFromModuleSrcs(ctx ModuleContext, srcs []string) (android.Path, android.Paths) {
-	if len(srcs) == 0 {
-		ctx.PropertyErrorf("srcs", "srcs must not be empty")
-	}
+func (compiler *baseCompiler) checkedCrateRootPath() (android.Path, error) {
+	return compiler.cachedCrateRootPath, compiler.cachedCrateRootError
+}
 
+func crateRootPath(ctx ModuleContext, compiler compiler) android.Path {
+	root, err := compiler.checkedCrateRootPath()
+	if err != nil {
+		ctx.PropertyErrorf("srcs", err.Error())
+	}
+	return root
+}
+
+// Returns the Path for the main source file along with Paths for generated source files from modules listed in srcs.
+func srcPathFromModuleSrcs(ctx ModuleContext, srcs []string) (android.Path, error) {
 	// The srcs can contain strings with prefix ":".
 	// They are dependent modules of this module, with android.SourceDepTag.
 	// They are not the main source file compiled by rustc.
@@ -514,19 +584,22 @@
 		}
 	}
 	if numSrcs > 1 {
-		ctx.PropertyErrorf("srcs", incorrectSourcesError)
+		return nil, errors.New(incorrectSourcesError)
 	}
 
 	// If a main source file is not provided we expect only a single SourceProvider module to be defined
 	// within srcs, with the expectation that the first source it provides is the entry point.
 	if srcIndex != 0 {
-		ctx.PropertyErrorf("srcs", "main source file must be the first in srcs")
+		return nil, errors.New("main source file must be the first in srcs")
 	} else if numSrcs > 1 {
-		ctx.PropertyErrorf("srcs", "only a single generated source module can be defined without a main source file.")
+		return nil, errors.New("only a single generated source module can be defined without a main source file.")
 	}
 
 	// TODO: b/297264540 - once all modules are sandboxed, we need to select the proper
 	// entry point file from Srcs rather than taking the first one
 	paths := android.PathsForModuleSrc(ctx, srcs)
-	return paths[srcIndex], paths[1:]
+	if len(paths) == 0 {
+		return nil, errors.New("srcs must not be empty")
+	}
+	return paths[srcIndex], nil
 }
diff --git a/rust/compiler_test.go b/rust/compiler_test.go
index ec6829a..89f4d1a 100644
--- a/rust/compiler_test.go
+++ b/rust/compiler_test.go
@@ -67,6 +67,7 @@
 func TestEnforceSingleSourceFile(t *testing.T) {
 
 	singleSrcError := "srcs can only contain one path for a rust file and source providers prefixed by \":\""
+	prebuiltSingleSrcError := "prebuilt libraries can only have one entry in srcs"
 
 	// Test libraries
 	testRustError(t, singleSrcError, `
@@ -90,7 +91,7 @@
 		}`)
 
 	// Test prebuilts
-	testRustError(t, singleSrcError, `
+	testRustError(t, prebuiltSingleSrcError, `
 		rust_prebuilt_dylib {
 			name: "foo-bar-prebuilt",
 			srcs: ["liby.so", "libz.so"],
diff --git a/rust/library.go b/rust/library.go
index 18bf0a0..c0ff741 100644
--- a/rust/library.go
+++ b/rust/library.go
@@ -15,6 +15,7 @@
 package rust
 
 import (
+	"errors"
 	"fmt"
 	"regexp"
 	"strings"
@@ -489,7 +490,7 @@
 	var outputFile android.ModuleOutPath
 	var ret buildOutput
 	var fileName string
-	crateRootPath := library.crateRootPath(ctx, deps)
+	crateRootPath := crateRootPath(ctx, library)
 
 	if library.sourceProvider != nil {
 		deps.srcProviderFiles = append(deps.srcProviderFiles, library.sourceProvider.Srcs()...)
@@ -584,15 +585,16 @@
 	return ret
 }
 
-func (library *libraryDecorator) crateRootPath(ctx ModuleContext, _ PathDeps) android.Path {
+func (library *libraryDecorator) checkedCrateRootPath() (android.Path, error) {
 	if library.sourceProvider != nil {
+		srcs := library.sourceProvider.Srcs()
+		if len(srcs) == 0 {
+			return nil, errors.New("Source provider generated 0 sources")
+		}
 		// Assume the first source from the source provider is the library entry point.
-		return library.sourceProvider.Srcs()[0]
-	} else if library.baseCompiler.Properties.Crate_root == nil {
-		path, _ := srcPathFromModuleSrcs(ctx, library.baseCompiler.Properties.Srcs)
-		return path
+		return srcs[0], nil
 	} else {
-		return android.PathForModuleSrc(ctx, *library.baseCompiler.Properties.Crate_root)
+		return library.baseCompiler.checkedCrateRootPath()
 	}
 }
 
@@ -607,7 +609,7 @@
 		return android.OptionalPath{}
 	}
 
-	return android.OptionalPathForPath(Rustdoc(ctx, library.crateRootPath(ctx, deps),
+	return android.OptionalPathForPath(Rustdoc(ctx, crateRootPath(ctx, library),
 		deps, flags))
 }
 
diff --git a/rust/prebuilt.go b/rust/prebuilt.go
index fe9d0b5..e35e510 100644
--- a/rust/prebuilt.go
+++ b/rust/prebuilt.go
@@ -76,6 +76,17 @@
 var _ exportedFlagsProducer = (*prebuiltProcMacroDecorator)(nil)
 var _ rustPrebuilt = (*prebuiltProcMacroDecorator)(nil)
 
+func prebuiltPath(ctx ModuleContext, prebuilt rustPrebuilt) android.Path {
+	srcs := android.PathsForModuleSrc(ctx, prebuilt.prebuiltSrcs())
+	if len(srcs) == 0 {
+		ctx.PropertyErrorf("srcs", "srcs must not be empty")
+	}
+	if len(srcs) > 1 {
+		ctx.PropertyErrorf("srcs", "prebuilt libraries can only have one entry in srcs (the prebuilt path)")
+	}
+	return srcs[0]
+}
+
 func PrebuiltLibraryFactory() android.Module {
 	module, _ := NewPrebuiltLibrary(android.HostAndDeviceSupported)
 	return module.Init()
@@ -148,11 +159,7 @@
 func (prebuilt *prebuiltLibraryDecorator) compile(ctx ModuleContext, flags Flags, deps PathDeps) buildOutput {
 	prebuilt.flagExporter.exportLinkDirs(android.PathsForModuleSrc(ctx, prebuilt.Properties.Link_dirs).Strings()...)
 	prebuilt.flagExporter.setProvider(ctx)
-
-	srcPath, paths := srcPathFromModuleSrcs(ctx, prebuilt.prebuiltSrcs())
-	if len(paths) > 0 {
-		ctx.PropertyErrorf("srcs", "prebuilt libraries can only have one entry in srcs (the prebuilt path)")
-	}
+	srcPath := prebuiltPath(ctx, prebuilt)
 	prebuilt.baseCompiler.unstrippedOutputFile = srcPath
 	return buildOutput{outputFile: srcPath}
 }
@@ -205,11 +212,7 @@
 func (prebuilt *prebuiltProcMacroDecorator) compile(ctx ModuleContext, flags Flags, deps PathDeps) buildOutput {
 	prebuilt.flagExporter.exportLinkDirs(android.PathsForModuleSrc(ctx, prebuilt.Properties.Link_dirs).Strings()...)
 	prebuilt.flagExporter.setProvider(ctx)
-
-	srcPath, paths := srcPathFromModuleSrcs(ctx, prebuilt.prebuiltSrcs())
-	if len(paths) > 0 {
-		ctx.PropertyErrorf("srcs", "prebuilt libraries can only have one entry in srcs (the prebuilt path)")
-	}
+	srcPath := prebuiltPath(ctx, prebuilt)
 	prebuilt.baseCompiler.unstrippedOutputFile = srcPath
 	return buildOutput{outputFile: srcPath}
 }
diff --git a/rust/proc_macro.go b/rust/proc_macro.go
index b93b24f..c18d5ec 100644
--- a/rust/proc_macro.go
+++ b/rust/proc_macro.go
@@ -78,8 +78,7 @@
 func (procMacro *procMacroDecorator) compile(ctx ModuleContext, flags Flags, deps PathDeps) buildOutput {
 	fileName := procMacro.getStem(ctx) + ctx.toolchain().ProcMacroSuffix()
 	outputFile := android.PathForModuleOut(ctx, fileName)
-
-	srcPath, _ := srcPathFromModuleSrcs(ctx, procMacro.baseCompiler.Properties.Srcs)
+	srcPath := crateRootPath(ctx, procMacro)
 	ret := TransformSrctoProcMacro(ctx, srcPath, deps, flags, outputFile)
 	procMacro.baseCompiler.unstrippedOutputFile = outputFile
 	return ret
diff --git a/rust/project_json.go b/rust/project_json.go
index 40aa7c7..83c16ca 100644
--- a/rust/project_json.go
+++ b/rust/project_json.go
@@ -17,7 +17,6 @@
 import (
 	"encoding/json"
 	"fmt"
-	"path"
 
 	"android/soong/android"
 )
@@ -60,8 +59,9 @@
 
 // crateInfo is used during the processing to keep track of the known crates.
 type crateInfo struct {
-	Idx  int            // Index of the crate in rustProjectJson.Crates slice.
-	Deps map[string]int // The keys are the module names and not the crate names.
+	Idx    int            // Index of the crate in rustProjectJson.Crates slice.
+	Deps   map[string]int // The keys are the module names and not the crate names.
+	Device bool           // True if the crate at idx was a device crate
 }
 
 type projectGeneratorSingleton struct {
@@ -77,85 +77,6 @@
 	android.RegisterParallelSingletonType("rust_project_generator", rustProjectGeneratorSingleton)
 }
 
-// sourceProviderVariantSource returns the path to the source file if this
-// module variant should be used as a priority.
-//
-// SourceProvider modules may have multiple variants considered as source
-// (e.g., x86_64 and armv8). For a module available on device, use the source
-// generated for the target. For a host-only module, use the source generated
-// for the host.
-func sourceProviderVariantSource(ctx android.SingletonContext, rModule *Module) (string, bool) {
-	rustLib, ok := rModule.compiler.(*libraryDecorator)
-	if !ok {
-		return "", false
-	}
-	if rustLib.source() {
-		switch rModule.hod {
-		case android.HostSupported, android.HostSupportedNoCross:
-			if rModule.Target().String() == ctx.Config().BuildOSTarget.String() {
-				src := rustLib.sourceProvider.Srcs()[0]
-				return src.String(), true
-			}
-		default:
-			if rModule.Target().String() == ctx.Config().AndroidFirstDeviceTarget.String() {
-				src := rustLib.sourceProvider.Srcs()[0]
-				return src.String(), true
-			}
-		}
-	}
-	return "", false
-}
-
-// sourceProviderSource finds the main source file of a source-provider crate.
-func sourceProviderSource(ctx android.SingletonContext, rModule *Module) (string, bool) {
-	rustLib, ok := rModule.compiler.(*libraryDecorator)
-	if !ok {
-		return "", false
-	}
-	if rustLib.source() {
-		// This is a source-variant, check if we are the right variant
-		// depending on the module configuration.
-		if src, ok := sourceProviderVariantSource(ctx, rModule); ok {
-			return src, true
-		}
-	}
-	foundSource := false
-	sourceSrc := ""
-	// Find the variant with the source and return its.
-	ctx.VisitAllModuleVariants(rModule, func(variant android.Module) {
-		if foundSource {
-			return
-		}
-		// All variants of a source provider library are libraries.
-		rVariant, _ := variant.(*Module)
-		variantLib, _ := rVariant.compiler.(*libraryDecorator)
-		if variantLib.source() {
-			sourceSrc, ok = sourceProviderVariantSource(ctx, rVariant)
-			if ok {
-				foundSource = true
-			}
-		}
-	})
-	if !foundSource {
-		ctx.Errorf("No valid source for source provider found: %v\n", rModule)
-	}
-	return sourceSrc, foundSource
-}
-
-// crateSource finds the main source file (.rs) for a crate.
-func crateSource(ctx android.SingletonContext, rModule *Module, comp *baseCompiler) (string, bool) {
-	// Basic libraries, executables and tests.
-	srcs := comp.Properties.Srcs
-	if len(srcs) != 0 {
-		return path.Join(ctx.ModuleDir(rModule), srcs[0]), true
-	}
-	// SourceProvider libraries.
-	if rModule.sourceProvider != nil {
-		return sourceProviderSource(ctx, rModule)
-	}
-	return "", false
-}
-
 // mergeDependencies visits all the dependencies for module and updates crate and deps
 // with any new dependency.
 func (singleton *projectGeneratorSingleton) mergeDependencies(ctx android.SingletonContext,
@@ -167,7 +88,7 @@
 			return
 		}
 		// Skip unsupported modules.
-		rChild, compChild, ok := isModuleSupported(ctx, child)
+		rChild, ok := isModuleSupported(ctx, child)
 		if !ok {
 			return
 		}
@@ -175,7 +96,7 @@
 		var childId int
 		cInfo, known := singleton.knownCrates[rChild.Name()]
 		if !known {
-			childId, ok = singleton.addCrate(ctx, rChild, compChild)
+			childId, ok = singleton.addCrate(ctx, rChild, make(map[string]int))
 			if !ok {
 				return
 			}
@@ -191,41 +112,22 @@
 	})
 }
 
-// isModuleSupported returns the RustModule and baseCompiler if the module
+// isModuleSupported returns the RustModule if the module
 // should be considered for inclusion in rust-project.json.
-func isModuleSupported(ctx android.SingletonContext, module android.Module) (*Module, *baseCompiler, bool) {
+func isModuleSupported(ctx android.SingletonContext, module android.Module) (*Module, bool) {
 	rModule, ok := module.(*Module)
 	if !ok {
-		return nil, nil, false
+		return nil, false
 	}
-	if rModule.compiler == nil {
-		return nil, nil, false
-	}
-	var comp *baseCompiler
-	switch c := rModule.compiler.(type) {
-	case *libraryDecorator:
-		comp = c.baseCompiler
-	case *binaryDecorator:
-		comp = c.baseCompiler
-	case *testDecorator:
-		comp = c.binaryDecorator.baseCompiler
-	case *procMacroDecorator:
-		comp = c.baseCompiler
-	case *toolchainLibraryDecorator:
-		comp = c.baseCompiler
-	default:
-		return nil, nil, false
-	}
-	return rModule, comp, true
+	return rModule, true
 }
 
 // addCrate adds a crate to singleton.project.Crates ensuring that required
 // dependencies are also added. It returns the index of the new crate in
 // singleton.project.Crates
-func (singleton *projectGeneratorSingleton) addCrate(ctx android.SingletonContext, rModule *Module, comp *baseCompiler) (int, bool) {
-	rootModule, ok := crateSource(ctx, rModule, comp)
-	if !ok {
-		ctx.Errorf("Unable to find source for valid module: %v", rModule)
+func (singleton *projectGeneratorSingleton) addCrate(ctx android.SingletonContext, rModule *Module, deps map[string]int) (int, bool) {
+	rootModule, err := rModule.compiler.checkedCrateRootPath()
+	if err != nil {
 		return 0, false
 	}
 
@@ -233,28 +135,33 @@
 
 	crate := rustProjectCrate{
 		DisplayName: rModule.Name(),
-		RootModule:  rootModule,
-		Edition:     comp.edition(),
+		RootModule:  rootModule.String(),
+		Edition:     rModule.compiler.edition(),
 		Deps:        make([]rustProjectDep, 0),
 		Cfg:         make([]string, 0),
 		Env:         make(map[string]string),
 		ProcMacro:   procMacro,
 	}
 
-	if comp.CargoOutDir().Valid() {
-		crate.Env["OUT_DIR"] = comp.CargoOutDir().String()
+	if rModule.compiler.cargoOutDir().Valid() {
+		crate.Env["OUT_DIR"] = rModule.compiler.cargoOutDir().String()
 	}
 
-	for _, feature := range comp.Properties.Features {
+	for _, feature := range rModule.compiler.features() {
 		crate.Cfg = append(crate.Cfg, "feature=\""+feature+"\"")
 	}
 
-	deps := make(map[string]int)
 	singleton.mergeDependencies(ctx, rModule, &crate, deps)
 
-	idx := len(singleton.project.Crates)
-	singleton.knownCrates[rModule.Name()] = crateInfo{Idx: idx, Deps: deps}
-	singleton.project.Crates = append(singleton.project.Crates, crate)
+	var idx int
+	if cInfo, ok := singleton.knownCrates[rModule.Name()]; ok {
+		idx = cInfo.Idx
+		singleton.project.Crates[idx] = crate
+	} else {
+		idx = len(singleton.project.Crates)
+		singleton.project.Crates = append(singleton.project.Crates, crate)
+	}
+	singleton.knownCrates[rModule.Name()] = crateInfo{Idx: idx, Deps: deps, Device: rModule.Device()}
 	return idx, true
 }
 
@@ -262,18 +169,23 @@
 // It visits the dependencies of the module depth-first so the dependency ID can be added to the current module. If the
 // current module is already in singleton.knownCrates, its dependencies are merged.
 func (singleton *projectGeneratorSingleton) appendCrateAndDependencies(ctx android.SingletonContext, module android.Module) {
-	rModule, comp, ok := isModuleSupported(ctx, module)
+	rModule, ok := isModuleSupported(ctx, module)
 	if !ok {
 		return
 	}
 	// If we have seen this crate already; merge any new dependencies.
 	if cInfo, ok := singleton.knownCrates[module.Name()]; ok {
+		// If we have a new device variant, override the old one
+		if !cInfo.Device && rModule.Device() {
+			singleton.addCrate(ctx, rModule, cInfo.Deps)
+			return
+		}
 		crate := singleton.project.Crates[cInfo.Idx]
 		singleton.mergeDependencies(ctx, rModule, &crate, cInfo.Deps)
 		singleton.project.Crates[cInfo.Idx] = crate
 		return
 	}
-	singleton.addCrate(ctx, rModule, comp)
+	singleton.addCrate(ctx, rModule, make(map[string]int))
 }
 
 func (singleton *projectGeneratorSingleton) GenerateBuildActions(ctx android.SingletonContext) {
diff --git a/rust/rust.go b/rust/rust.go
index 15144ac..d4d33c7 100644
--- a/rust/rust.go
+++ b/rust/rust.go
@@ -487,44 +487,6 @@
 	CrateName string
 }
 
-type compiler interface {
-	initialize(ctx ModuleContext)
-	compilerFlags(ctx ModuleContext, flags Flags) Flags
-	cfgFlags(ctx ModuleContext, flags Flags) Flags
-	featureFlags(ctx ModuleContext, flags Flags) Flags
-	compilerProps() []interface{}
-	compile(ctx ModuleContext, flags Flags, deps PathDeps) buildOutput
-	compilerDeps(ctx DepsContext, deps Deps) Deps
-	crateName() string
-	rustdoc(ctx ModuleContext, flags Flags, deps PathDeps) android.OptionalPath
-
-	// Output directory in which source-generated code from dependencies is
-	// copied. This is equivalent to Cargo's OUT_DIR variable.
-	CargoOutDir() android.OptionalPath
-
-	// CargoPkgVersion returns the value of the Cargo_pkg_version property.
-	CargoPkgVersion() string
-
-	// CargoEnvCompat returns whether Cargo environment variables should be used.
-	CargoEnvCompat() bool
-
-	inData() bool
-	install(ctx ModuleContext)
-	relativeInstallPath() string
-	everInstallable() bool
-
-	nativeCoverage() bool
-
-	Disabled() bool
-	SetDisabled()
-
-	stdLinkage(ctx *depsContext) RustLinkage
-	noStdlibs() bool
-
-	unstrippedOutputFilePath() android.Path
-	strippedOutputFilePath() android.OptionalPath
-}
-
 type exportedFlagsProducer interface {
 	exportLinkDirs(...string)
 	exportLinkObjects(...string)