compiler: fix import alias handling

pkg/compiler/analysis.go

@@ -246,7 +246,11 @@ func (c *codegen) analyzeFuncUsage() funcUsage {
 			case *ast.CallExpr:
 				switch t := n.Fun.(type) {
 				case *ast.Ident:
-					usage[c.getIdentName("", t.Name)] = true
+					var pkgPath string
+					if !isMain {
+						pkgPath = pkg.Path()
+					}
+					usage[c.getIdentName(pkgPath, t.Name)] = true
 				case *ast.SelectorExpr:
 					name, _ := c.getFuncNameFromSelector(t)
 					usage[name] = true
@@ -254,7 +258,7 @@ func (c *codegen) analyzeFuncUsage() funcUsage {
 			case *ast.FuncDecl:
 				// exported functions are always assumed to be used
 				if isMain && n.Name.IsExported() {
-					usage[c.getFuncNameFromDecl(pkg.Path(), n)] = true
+					usage[c.getFuncNameFromDecl("", n)] = true
 				}
 			}
 			return true

pkg/compiler/codegen.go

@@ -1986,7 +1986,11 @@ func (c *codegen) compile(info *buildInfo, pkg *loader.PackageInfo) error {
 			case *ast.FuncDecl:
 				// Don't convert the function if it's not used. This will save a lot
 				// of bytecode space.
-				name := c.getFuncNameFromDecl(pkg.Path(), n)
+				pkgPath := ""
+				if pkg != c.mainPkg.Pkg { // not a main package
+					pkgPath = pkg.Path()
+				}
+				name := c.getFuncNameFromDecl(pkgPath, n)
 				if !isInitFunc(n) && !isDeployFunc(n) && funUsage.funcUsed(name) &&
 					(!isInteropPath(pkg.Path()) && !canInline(pkg.Path())) {
 					c.convertFuncDecl(f, n, pkg)

pkg/compiler/import_test.go

@@ -48,3 +48,16 @@ func TestMultipleDirFileImport(t *testing.T) {
 	`
 	eval(t, src, big.NewInt(1))
 }
+
+func TestImportNameSameAsOwn(t *testing.T) {
+	src := `package foo
+	import "github.com/nspcc-dev/neo-go/pkg/compiler/testdata/foo"
+	func get3() int { return 3 }
+	func Main() int {
+		return get3()
+	}
+	func unused() int {
+		return foo.Bar()
+	}`
+	eval(t, src, big.NewInt(3))
+}