Allow stable rust (#118)

This pr introduces some cargo features. For `swc_common` and `swc_ecma_ast`, it introduces a feature flag `fold`.
`Fold` and `Visit` traits exist only if the feature is enabled.

For `swc_ecma_parser`, flag called `verify` is added. When disabled, we skip checking of validity of some expressions.

e.g. `{foo = bar}`

Verification is disabled by default it requires nightly compiler

Author: kdy1

.cargo/config

@@ -2,10 +2,8 @@
 [build]
 rustflags = [
     "--cfg", "procmacro2_semver_exempt",
-    "--cfg", "parallel_queries",
 ]
 
 rustdocflags = [
     "--cfg", "procmacro2_semver_exempt",
-    "--cfg", "parallel_queries",
 ]

common/Cargo.toml

@@ -1,17 +1,30 @@
 [package]
 name = "swc_common"
-version = "0.1.4"
+version = "0.2.0"
 authors = ["강동윤 <[email protected]>"]
 license = "Apache-2.0/MIT"
 repository = "https://github.com/swc-project/swc.git"
 documentation = "https://swc-project.github.io/rustdoc/swc_common/"
 description = "Common utilities for the swc project."
 
+[features]
+default = []
+# Enable folder and visitor. Requires nightly compiler.
+fold = ["ast_node/fold"]
+
+
 [dependencies]
-ast_node = { version = "0.2", path = "../macros/ast_node" }
+ast_node = { version = "0.3", path = "../macros/ast_node" }
 string_cache = "0.7"
 either = "1.5"
-rustc-ap-rustc_errors = "313"
-rustc-ap-syntax = "313"
-rustc-ap-rustc_data_structures = "313"
-rustc-ap-syntax_pos = "313"
+scoped-tls = { version = "0.1.1", features = ["nightly"] }
+unicode-width = "0.1.4"
+cfg-if = "0.1.2"
+log = "0.4"
+atty = "0.2"
+parking_lot = "0.6"
+fxhash = "0.2"
+termcolor = "1.0"
+rayon = "1"
+rayon-core = "1"
+owning_ref = "0.4"