Change to no_smartstring feature.

Cargo.toml

@@ -19,10 +19,12 @@ categories = ["no-std", "embedded", "wasm", "parser-implementations"]
 smallvec = { version = "1.6", default-features = false, features = ["union"] }
 ahash = { version = "0.7", default-features = false }
 num-traits = { version = "0.2", default_features = false }
+#smartstring = { version = "0.2.6" }
+smartstring = { git = "https://github.com/okready/smartstring", branch = "fix-no_std-builds", default_features = false }
 rhai_codegen = { version = "0.3.4", path = "codegen", features = ["metadata"] }
 
 [features]
-default = ["smartstring"]
+default = []
 unchecked = []                  # unchecked arithmetic
 sync = []                       # restrict to only types that implement Send + Sync
 no_optimize = []                # no script optimizer
@@ -40,6 +42,7 @@ internals = []                  # expose internal data structures
 unicode-xid-ident = ["unicode-xid"] # allow Unicode Standard Annex #31 for identifiers.
 metadata = ["serde_json"]       # enable exporting functions metadata
 
+no_smartstring = []             # set Identifier=ImmutableString
 no_std = ["smallvec/union", "num-traits/libm", "core-error", "libm", "ahash/compile-time-rng"]
 
 # compiling for WASM
@@ -75,10 +78,6 @@ default_features = false
 features = ["alloc"]
 optional = true
 
-[dependencies.smartstring]
-version = "0.2.6"
-optional = true
-
 [dependencies.unicode-xid]
 version = "0.2"
 default_features = false