stage2: implement error notes and regress -femit-zir

 * Implement error notes
   - note: other symbol exported here
   - note: previous else prong is here
   - note: previous '_' prong is here
 * Add Compilation.CObject.ErrorMsg. This object properly converts to
   AllErrors.Message when the time comes.
 * Add Compilation.CObject.failure_retryable. Properly handles
   out-of-memory and other transient failures.
 * Introduce Module.SrcLoc which has not only a byte offset but also
   references the file which the byte offset applies to.
 * Scope.Block now contains both a pointer to the "owner" Decl and the
   "source" Decl. As an example, during inline function call, the
   "owner" will be the Decl of the caller and the "source" will be the
   Decl of the callee.
 * Module.ErrorMsg now sports a `file_scope` field so that notes can
   refer to source locations in a file other than the parent error
   message.
 * Some instances where a `*Scope` was stored, now store a
   `*Scope.Container`.
 * Some methods in the `Scope` namespace were moved to the more specific
   type, since there was only an implementation for one particular tag.
   - `removeDecl` moved to `Scope.Container`
   - `destroy` moved to `Scope.File`
 * Two kinds of Scope deleted:
   - zir_module
   - decl
 * astgen: properly use DeclVal / DeclRef. DeclVal was incorrectly
   changed to be a reference; this commit fixes it. Fewer ZIR
   instructions processed as a result.
   - declval_in_module is renamed to declval
   - previous declval ZIR instruction is deleted; it was only for .zir
     files.
 * Test harness: friendlier diagnostics when an unexpected set of errors
   is encountered.
 * zir_sema: fix analyzeInstBlockFlat by properly calling resolvingInst
   on the last zir instruction in the block.

Compile log implementation:
 * Write to a buffer rather than directly to stderr.
 * Only keep track of 1 callsite per Decl.
 * No longer mutate the ZIR Inst struct data.
 * "Compile log statement found" errors are only emitted when there are
   no other compile errors.

-femit-zir and support for .zir source files is regressed. If we wanted
to support this again, outputting .zir would need to be done as yet
another backend rather than in the haphazard way it was previously
implemented.

For parsing .zir, it was implemented previously in a way that was not
helpful for debugging. We need tighter integration with the test harness
for it to be useful; so clearly a rewrite is needed. Given that a
rewrite is needed, and it was getting in the way of progress and
organization of the rest of stage2, I regressed the feature.

1 files changed, 14 insertions, 33 deletions

diff --git a/src/main.zig b/src/main.zig
index 867aa348b1..13bea13a5e 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -221,7 +221,6 @@ const usage_build_generic =
     \\
     \\Supported file types:
     \\                    .zig    Zig source code
-    \\                    .zir    Zig Intermediate Representation code
     \\                      .o    ELF object file
     \\                      .o    MACH-O (macOS) object file
     \\                    .obj    COFF (Windows) object file
@@ -245,8 +244,6 @@ const usage_build_generic =
     \\  -fno-emit-bin             Do not output machine code
     \\  -femit-asm[=path]         Output .s (assembly code)
     \\  -fno-emit-asm             (default) Do not output .s (assembly code)
-    \\  -femit-zir[=path]         Produce a .zir file with Zig IR
-    \\  -fno-emit-zir             (default) Do not produce a .zir file with Zig IR
     \\  -femit-llvm-ir[=path]     Produce a .ll file with LLVM IR (requires LLVM extensions)
     \\  -fno-emit-llvm-ir         (default) Do not produce a .ll file with LLVM IR
     \\  -femit-h[=path]           Generate a C header file (.h)
@@ -1631,18 +1628,12 @@ fn buildOutputType(
     var emit_docs_resolved = try emit_docs.resolve("docs");
     defer emit_docs_resolved.deinit();
 
-    const zir_out_path: ?[]const u8 = switch (emit_zir) {
-        .no => null,
-        .yes_default_path => blk: {
-            if (root_src_file) |rsf| {
-                if (mem.endsWith(u8, rsf, ".zir")) {
-                    break :blk try std.fmt.allocPrint(arena, "{s}.out.zir", .{root_name});
-                }
-            }
-            break :blk try std.fmt.allocPrint(arena, "{s}.zir", .{root_name});
+    switch (emit_zir) {
+        .no => {},
+        .yes_default_path, .yes => {
+            fatal("The -femit-zir implementation has been intentionally deleted so that it can be rewritten as a proper backend.", .{});
         },
-        .yes => |p| p,
-    };
+    }
 
     const root_pkg: ?*Package = if (root_src_file) |src_path| blk: {
         if (main_pkg_path) |p| {
@@ -1753,7 +1744,7 @@ fn buildOutputType(
         .dll_export_fns = dll_export_fns,
         .object_format = object_format,
         .optimize_mode = optimize_mode,
-        .keep_source_files_loaded = zir_out_path != null,
+        .keep_source_files_loaded = false,
         .clang_argv = clang_argv.items,
         .lld_argv = lld_argv.items,
         .lib_dirs = lib_dirs.items,
@@ -1845,7 +1836,7 @@ fn buildOutputType(
         }
     };
 
-    updateModule(gpa, comp, zir_out_path, hook) catch |err| switch (err) {
+    updateModule(gpa, comp, hook) catch |err| switch (err) {
         error.SemanticAnalyzeFail => if (!watch) process.exit(1),
         else => |e| return e,
     };
@@ -1980,7 +1971,7 @@ fn buildOutputType(
                 if (output_mode == .Exe) {
                     try comp.makeBinFileWritable();
                 }
-                updateModule(gpa, comp, zir_out_path, hook) catch |err| switch (err) {
+                updateModule(gpa, comp, hook) catch |err| switch (err) {
                     error.SemanticAnalyzeFail => continue,
                     else => |e| return e,
                 };
@@ -2003,7 +1994,7 @@ const AfterUpdateHook = union(enum) {
     update: []const u8,
 };
 
-fn updateModule(gpa: *Allocator, comp: *Compilation, zir_out_path: ?[]const u8, hook: AfterUpdateHook) !void {
+fn updateModule(gpa: *Allocator, comp: *Compilation, hook: AfterUpdateHook) !void {
     try comp.update();
 
     var errors = try comp.getAllErrorsAlloc();
@@ -2013,6 +2004,10 @@ fn updateModule(gpa: *Allocator, comp: *Compilation, zir_out_path: ?[]const u8,
         for (errors.list) |full_err_msg| {
             full_err_msg.renderToStdErr();
         }
+        const log_text = comp.getCompileLogOutput();
+        if (log_text.len != 0) {
+            std.debug.print("\nCompile Log Output:\n{s}", .{log_text});
+        }
         return error.SemanticAnalyzeFail;
     } else switch (hook) {
         .none => {},
@@ -2024,20 +2019,6 @@ fn updateModule(gpa: *Allocator, comp: *Compilation, zir_out_path: ?[]const u8,
             .{},
         ),
     }
-
-    if (zir_out_path) |zop| {
-        const module = comp.bin_file.options.module orelse
-            fatal("-femit-zir with no zig source code", .{});
-        var new_zir_module = try zir.emit(gpa, module);
-        defer new_zir_module.deinit(gpa);
-
-        const baf = try io.BufferedAtomicFile.create(gpa, fs.cwd(), zop, .{});
-        defer baf.destroy();
-
-        try new_zir_module.writeToStream(gpa, baf.writer());
-
-        try baf.finish();
-    }
 }
 
 fn cmdTranslateC(comp: *Compilation, arena: *Allocator, enable_cache: bool) !void {
@@ -2506,7 +2487,7 @@ pub fn cmdBuild(gpa: *Allocator, arena: *Allocator, args: []const []const u8) !v
         };
         defer comp.destroy();
 
-        try updateModule(gpa, comp, null, .none);
+        try updateModule(gpa, comp, .none);
         try comp.makeBinFileExecutable();
 
         child_argv.items[argv_index_exe] = try comp.bin_file.options.emit.?.directory.join(