cranelift-isle: no_std support (#12236)

* cranelift-isle: no_std support

* add extern crate alloc, and remove unnessesary imports

* allow unused imports

* remove extern crate alloc

* add an import of core::marker::PhantomData

* add extern crate alloc and core

Author: the-ssd

cranelift/isle/isle/isle_examples/link/borrows_main.rs

@@ -1,3 +1,6 @@
+extern crate alloc;
+extern crate core;
+
 mod borrows;
 
 #[derive(Clone)]

cranelift/isle/isle/isle_examples/link/iflets_main.rs

@@ -1,3 +1,6 @@
+extern crate alloc;
+extern crate core;
+
 mod iflets;
 
 struct Context;

cranelift/isle/isle/isle_examples/link/multi_constructor_main.rs

@@ -1,3 +1,6 @@
+extern crate alloc;
+extern crate core;
+
 mod multi_constructor;
 use multi_constructor::{ContextIter, IntoContextIter};
 

cranelift/isle/isle/isle_examples/link/multi_extractor_main.rs

@@ -1,3 +1,6 @@
+extern crate alloc;
+extern crate core;
+
 mod multi_extractor;
 
 use multi_extractor::{ContextIter, IntoContextIter};

cranelift/isle/isle/isle_examples/link/test_main.rs

@@ -1,3 +1,6 @@
+extern crate alloc;
+extern crate core;
+
 mod test;
 
 struct Context;

cranelift/isle/isle/isle_examples/run/iconst_main.rs

@@ -1,3 +1,6 @@
+extern crate alloc;
+extern crate core;
+
 mod iconst;
 
 struct Context;

cranelift/isle/isle/isle_examples/run/let_shadowing_main.rs

@@ -1,3 +1,6 @@
+extern crate alloc;
+extern crate core;
+
 mod let_shadowing;
 
 struct Context;

cranelift/isle/isle/src/codegen.rs

@@ -166,7 +166,7 @@ impl<'a> Codegen<'a> {
         }
 
         writeln!(code, "\nuse super::*;  // Pulls in all external types.").unwrap();
-        writeln!(code, "use std::marker::PhantomData;").unwrap();
+        writeln!(code, "use core::marker::PhantomData;").unwrap();
     }
 
     fn generate_trait_sig(&self, code: &mut String, indent: &str, sig: &ExternalSig) {
@@ -271,38 +271,38 @@ pub trait Length {{
     fn len(&self) -> usize;
 }}
 
-impl<T> Length for std::vec::Vec<T> {{
+impl<T> Length for alloc::vec::Vec<T> {{
     fn len(&self) -> usize {{
-        std::vec::Vec::len(self)
+        alloc::vec::Vec::len(self)
     }}
 }}
 
 pub struct ContextIterWrapper<I, C> {{
     iter: I,
-    _ctx: std::marker::PhantomData<C>,
+    _ctx: core::marker::PhantomData<C>,
 }}
 impl<I: Default, C> Default for ContextIterWrapper<I, C> {{
     fn default() -> Self {{
         ContextIterWrapper {{
             iter: I::default(),
-            _ctx: std::marker::PhantomData
+            _ctx: core::marker::PhantomData
         }}
     }}
 }}
-impl<I, C> std::ops::Deref for ContextIterWrapper<I, C> {{
+impl<I, C> core::ops::Deref for ContextIterWrapper<I, C> {{
     type Target = I;
     fn deref(&self) -> &I {{
         &self.iter
     }}
 }}
-impl<I, C> std::ops::DerefMut for ContextIterWrapper<I, C> {{
+impl<I, C> core::ops::DerefMut for ContextIterWrapper<I, C> {{
     fn deref_mut(&mut self) -> &mut I {{
         &mut self.iter
     }}
 }}
 impl<I: Iterator, C: Context> From<I> for ContextIterWrapper<I, C> {{
     fn from(iter: I) -> Self {{
-        Self {{ iter, _ctx: std::marker::PhantomData }}
+        Self {{ iter, _ctx: core::marker::PhantomData }}
     }}
 }}
 impl<I: Iterator, C: Context> ContextIter for ContextIterWrapper<I, C> {{
@@ -322,7 +322,7 @@ impl<I: IntoIterator, C: Context> IntoContextIter for ContextIterWrapper<I, C> {
     fn into_context_iter(self) -> Self::IntoIter {{
         ContextIterWrapper {{
             iter: self.iter.into_iter(),
-            _ctx: std::marker::PhantomData
+            _ctx: core::marker::PhantomData
         }}
     }}
 }}