Remove thiserror dependency from cranelift_codegen

cranelift/codegen/src/isa/mod.rs

@@ -69,7 +69,6 @@ use core::fmt;
 use core::fmt::{Debug, Formatter};
 use core::hash::Hasher;
 use target_lexicon::{triple, Architecture, OperatingSystem, PointerWidth, Triple};
-use thiserror::Error;
 
 #[cfg(feature = "riscv")]
 mod riscv;
@@ -178,17 +177,28 @@ pub fn lookup_by_name(name: &str) -> Result<Builder, LookupError> {
 }
 
 /// Describes reason for target lookup failure
-#[derive(Error, PartialEq, Eq, Copy, Clone, Debug)]
+#[derive(PartialEq, Eq, Copy, Clone, Debug)]
 pub enum LookupError {
     /// Support for this target was disabled in the current build.
-    #[error("Support for this target is disabled")]
     SupportDisabled,
 
     /// Support for this target has not yet been implemented.
-    #[error("Support for this target has not been implemented yet")]
     Unsupported,
 }
 
+impl std::error::Error for LookupError {}
+
+impl fmt::Display for LookupError {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        match self {
+            LookupError::SupportDisabled => write!(f, "Support for this target is disabled"),
+            LookupError::Unsupported => {
+                write!(f, "Support for this target has not been implemented yet")
+            }
+        }
+    }
+}
+
 /// Builder for a `TargetIsa`.
 /// Modify the ISA-specific settings before creating the `TargetIsa` trait object with `finish`.
 #[derive(Clone)]

cranelift/codegen/src/isa/unwind/systemv.rs

@@ -6,7 +6,6 @@ use crate::isa::unwind::UnwindInst;
 use crate::result::{CodegenError, CodegenResult};
 use alloc::vec::Vec;
 use gimli::write::{Address, FrameDescriptionEntry};
-use thiserror::Error;
 
 #[cfg(feature = "enable-serde")]
 use serde::{Deserialize, Serialize};
@@ -15,16 +14,30 @@ type Register = u16;
 
 /// Enumerate the errors possible in mapping Cranelift registers to their DWARF equivalent.
 #[allow(missing_docs)]
-#[derive(Error, Debug, PartialEq, Eq)]
+#[derive(Debug, PartialEq, Eq)]
 pub enum RegisterMappingError {
-    #[error("unable to find bank for register info")]
     MissingBank,
-    #[error("register mapping is currently only implemented for x86_64")]
     UnsupportedArchitecture,
-    #[error("unsupported register bank: {0}")]
     UnsupportedRegisterBank(&'static str),
 }
 
+impl std::error::Error for RegisterMappingError {}
+
+impl std::fmt::Display for RegisterMappingError {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        match self {
+            RegisterMappingError::MissingBank => write!(f, "unable to find bank for register info"),
+            RegisterMappingError::UnsupportedArchitecture => write!(
+                f,
+                "register mapping is currently only implemented for x86_64"
+            ),
+            RegisterMappingError::UnsupportedRegisterBank(bank) => {
+                write!(f, "unsupported register bank: {}", bank)
+            }
+        }
+    }
+}
+
 // This mirrors gimli's CallFrameInstruction, but is serializable
 // This excludes CfaExpression, Expression, ValExpression due to
 // https://github.com/gimli-rs/gimli/issues/513.