Add tests to allocation methods and fix is_null()

compiler/stable_mir/src/mir/body.rs

@@ -21,7 +21,7 @@ pub struct Body {
     pub(super) arg_count: usize,
 
     /// Debug information pertaining to user variables, including captures.
-    pub(super) var_debug_info: Vec<VarDebugInfo>,
+    pub var_debug_info: Vec<VarDebugInfo>,
 }
 
 pub type BasicBlockIdx = usize;
@@ -616,6 +616,24 @@ pub struct VarDebugInfo {
     pub argument_index: Option<u16>,
 }
 
+impl VarDebugInfo {
+    /// Return a local variable if this info is related to one.
+    pub fn local(&self) -> Option<Local> {
+        match &self.value {
+            VarDebugInfoContents::Place(place) if place.projection.is_empty() => Some(place.local),
+            VarDebugInfoContents::Place(_) | VarDebugInfoContents::Const(_) => None,
+        }
+    }
+
+    /// Return a constant if this info is related to one.
+    pub fn constant(&self) -> Option<&ConstOperand> {
+        match &self.value {
+            VarDebugInfoContents::Place(_) => None,
+            VarDebugInfoContents::Const(const_op) => Some(const_op),
+        }
+    }
+}
+
 pub type SourceScope = u32;
 
 #[derive(Clone, Debug, Eq, PartialEq)]

compiler/stable_mir/src/ty.rs

@@ -901,6 +901,7 @@ impl Allocation {
         read_target_uint(&raw)
     }
 
+    /// Read this allocation and try to convert it to an unassigned integer.
     pub fn read_uint(&self) -> Result<u128, Error> {
         if self.bytes.len() > 16 {
             return Err(error!("Allocation is bigger than largest integer"));
@@ -909,6 +910,7 @@ impl Allocation {
         read_target_uint(&raw)
     }
 
+    /// Read this allocation and try to convert it to a signed integer.
     pub fn read_int(&self) -> Result<i128, Error> {
         if self.bytes.len() > 16 {
             return Err(error!("Allocation is bigger than largest integer"));
@@ -917,6 +919,7 @@ impl Allocation {
         read_target_int(&raw)
     }
 
+    /// Read this allocation and try to convert it to a boolean.
     pub fn read_bool(&self) -> Result<bool, Error> {
         match self.read_int()? {
             0 => Ok(false),
@@ -925,13 +928,14 @@ impl Allocation {
         }
     }
 
+    /// Read this allocation as a pointer and return whether it represents a `null` pointer.
     pub fn is_null(&self) -> Result<bool, Error> {
         let len = self.bytes.len();
         let ptr_len = MachineInfo::target_pointer_width().bytes();
         if len != ptr_len {
             return Err(error!("Expected width of pointer (`{ptr_len}`), but found: `{len}`"));
         }
-        Ok(self.read_uint()? == 0)
+        Ok(self.read_uint()? == 0 && self.provenance.ptrs.is_empty())
     }
 }