[naga spv-out] Make write_block and its types private.

Make `naga:🔙:spv::BlockContext::write_block` private to
`naga:🔙:spv::block`. Introduce a new `pub(super)` function,
`write_function_body`, for `Writer::write_function` to call.

Make `BlockExit` private to `naga:🔙:spv::block`.

Move `LoopContext` from `naga:🔙:spv` into
`naga:🔙:spv::block`, and make it private.

naga/src/back/spv/block.rs

@@ -4,8 +4,7 @@ Implementations for `BlockContext` methods.
 
 use super::{
     helpers, index::BoundsCheckResult, make_local, selection::Selection, Block, BlockContext,
-    Dimension, Error, Instruction, LocalType, LookupType, LoopContext, ResultMember, Writer,
-    WriterFlags,
+    Dimension, Error, Instruction, LocalType, LookupType, ResultMember, Writer, WriterFlags,
 };
 use crate::{arena::Handle, proc::TypeResolution, Statement};
 use spirv::Word;
@@ -39,7 +38,7 @@ enum ExpressionPointer {
 }
 
 /// The termination statement to be added to the end of the block
-pub enum BlockExit {
+enum BlockExit {
     /// Generates an OpReturn (void return)
     Return,
     /// Generates an OpBranch to the specified block
@@ -60,6 +59,12 @@ pub enum BlockExit {
     },
 }
 
+#[derive(Clone, Copy, Default)]
+struct LoopContext {
+    continuing_id: Option<Word>,
+    break_id: Option<Word>,
+}
+
 #[derive(Debug)]
 pub(crate) struct DebugInfoInner<'a> {
     pub source_code: &'a str,
@@ -2060,7 +2065,7 @@ impl<'w> BlockContext<'w> {
         }
     }
 
-    pub(super) fn write_block(
+    fn write_block(
         &mut self,
         label_id: Word,
         naga_block: &crate::Block,
@@ -2721,4 +2726,20 @@ impl<'w> BlockContext<'w> {
         self.function.consume(block, termination);
         Ok(())
     }
+
+    pub(super) fn write_function_body(
+        &mut self,
+        entry_id: Word,
+        debug_info: Option<&DebugInfoInner>,
+    ) -> Result<(), Error> {
+        self.write_block(
+            entry_id,
+            &self.ir_function.body,
+            super::block::BlockExit::Return,
+            LoopContext::default(),
+            debug_info,
+        )?;
+
+        Ok(())
+    }
 }

naga/src/back/spv/mod.rs

@@ -665,12 +665,6 @@ impl BlockContext<'_> {
     }
 }
 
-#[derive(Clone, Copy, Default)]
-struct LoopContext {
-    continuing_id: Option<Word>,
-    break_id: Option<Word>,
-}
-
 pub struct Writer {
     physical_layout: PhysicalLayout,
     logical_layout: LogicalLayout,

naga/src/back/spv/writer.rs

@@ -3,7 +3,7 @@ use super::{
     helpers::{contains_builtin, global_needs_wrapper, map_storage_class},
     make_local, Block, BlockContext, CachedConstant, CachedExpressions, DebugInfo,
     EntryPointContext, Error, Function, FunctionArgument, GlobalVariable, IdGenerator, Instruction,
-    LocalType, LocalVariable, LogicalLayout, LookupFunctionType, LookupType, LoopContext, Options,
+    LocalType, LocalVariable, LogicalLayout, LookupFunctionType, LookupType, Options,
     PhysicalLayout, PipelineOptions, ResultMember, Writer, WriterFlags, BITS_PER_BYTE,
 };
 use crate::{
@@ -756,13 +756,7 @@ impl Writer {
             next_id
         };
 
-        context.write_block(
-            main_id,
-            &ir_function.body,
-            super::block::BlockExit::Return,
-            LoopContext::default(),
-            debug_info.as_ref(),
-        )?;
+        context.write_function_body(main_id, debug_info.as_ref())?;
 
         // Consume the `BlockContext`, ending its borrows and letting the
         // `Writer` steal back its cached expression table and temp_list.