link: remove union types which are now internal to backends

src/Module.zig

@@ -328,8 +328,6 @@ pub const ErrorInt = u32;
 pub const Export = struct {
     options: std.builtin.ExportOptions,
     src: LazySrcLoc,
-    /// Represents the position of the export, if any, in the output file.
-    link: link.File.Export,
     /// The Decl that performs the export. Note that this is *not* the Decl being exported.
     owner_decl: Decl.Index,
     /// The Decl containing the export statement.  Inline function calls
@@ -533,16 +531,8 @@ pub const Decl = struct {
     /// What kind of a declaration is this.
     kind: Kind,
 
-    /// Represents the position of the code in the output file.
-    /// This is populated regardless of semantic analysis and code generation.
-    link: link.File.LinkBlock,
-
-    /// Represents the function in the linked output file, if the `Decl` is a function.
-    /// This is stored here and not in `Fn` because `Decl` survives across updates but
-    /// `Fn` does not.
-    /// TODO Look into making `Fn` a longer lived structure and moving this field there
-    /// to save on memory usage.
-    fn_link: link.File.LinkFn,
+    /// TODO remove this once Wasm backend catches up
+    fn_link: ?link.File.Wasm.FnData = null,
 
     /// The shallow set of other decls whose typed_value could possibly change if this Decl's
     /// typed_value is modified.
@@ -5258,27 +5248,9 @@ pub fn clearDecl(
         if (decl.ty.isFnOrHasRuntimeBits()) {
             mod.comp.bin_file.freeDecl(decl_index);
 
-            // TODO instead of a union, put this memory trailing Decl objects,
-            // and allow it to be variably sized.
-            decl.link = switch (mod.comp.bin_file.tag) {
-                .coff => .{ .coff = {} },
-                .elf => .{ .elf = {} },
-                .macho => .{ .macho = {} },
-                .plan9 => .{ .plan9 = {} },
-                .c => .{ .c = {} },
-                .wasm => .{ .wasm = {} },
-                .spirv => .{ .spirv = {} },
-                .nvptx => .{ .nvptx = {} },
-            };
             decl.fn_link = switch (mod.comp.bin_file.tag) {
-                .coff => .{ .coff = {} },
-                .elf => .{ .elf = {} },
-                .macho => .{ .macho = {} },
-                .plan9 => .{ .plan9 = {} },
-                .c => .{ .c = {} },
-                .wasm => .{ .wasm = link.File.Wasm.FnData.empty },
-                .spirv => .{ .spirv = {} },
-                .nvptx => .{ .nvptx = {} },
+                .wasm => link.File.Wasm.FnData.empty,
+                else => null,
             };
         }
         if (decl.getInnerNamespace()) |namespace| {
@@ -5680,25 +5652,9 @@ pub fn allocateNewDecl(
         .deletion_flag = false,
         .zir_decl_index = 0,
         .src_scope = src_scope,
-        .link = switch (mod.comp.bin_file.tag) {
-            .coff => .{ .coff = {} },
-            .elf => .{ .elf = {} },
-            .macho => .{ .macho = {} },
-            .plan9 => .{ .plan9 = {} },
-            .c => .{ .c = {} },
-            .wasm => .{ .wasm = {} },
-            .spirv => .{ .spirv = {} },
-            .nvptx => .{ .nvptx = {} },
-        },
         .fn_link = switch (mod.comp.bin_file.tag) {
-            .coff => .{ .coff = {} },
-            .elf => .{ .elf = {} },
-            .macho => .{ .macho = {} },
-            .plan9 => .{ .plan9 = {} },
-            .c => .{ .c = {} },
-            .wasm => .{ .wasm = link.File.Wasm.FnData.empty },
-            .spirv => .{ .spirv = {} },
-            .nvptx => .{ .nvptx = {} },
+            .wasm => link.File.Wasm.FnData.empty,
+            else => null,
         },
         .generation = 0,
         .is_pub = false,

src/Sema.zig

@@ -5564,16 +5564,6 @@ pub fn analyzeExport(
             .visibility = borrowed_options.visibility,
         },
         .src = src,
-        .link = switch (mod.comp.bin_file.tag) {
-            .coff => .{ .coff = {} },
-            .elf => .{ .elf = {} },
-            .macho => .{ .macho = {} },
-            .plan9 => .{ .plan9 = {} },
-            .c => .{ .c = {} },
-            .wasm => .{ .wasm = {} },
-            .spirv => .{ .spirv = {} },
-            .nvptx => .{ .nvptx = {} },
-        },
         .owner_decl = sema.owner_decl_index,
         .src_decl = block.src_decl,
         .exported_decl = exported_decl_index,

src/arch/wasm/CodeGen.zig

@@ -1194,7 +1194,7 @@ fn genFunc(func: *CodeGen) InnerError!void {
     const fn_info = func.decl.ty.fnInfo();
     var func_type = try genFunctype(func.gpa, fn_info.cc, fn_info.param_types, fn_info.return_type, func.target);
     defer func_type.deinit(func.gpa);
-    func.decl.fn_link.wasm.type_index = try func.bin_file.putOrGetFuncType(func_type);
+    func.decl.fn_link.?.type_index = try func.bin_file.putOrGetFuncType(func_type);
 
     var cc_result = try func.resolveCallingConventionValues(func.decl.ty);
     defer cc_result.deinit(func.gpa);
@@ -2129,12 +2129,12 @@ fn airCall(func: *CodeGen, inst: Air.Inst.Index, modifier: std.builtin.CallModif
             defer func_type.deinit(func.gpa);
             const atom_index = try func.bin_file.getOrCreateAtomForDecl(extern_fn.data.owner_decl);
             const atom = func.bin_file.getAtomPtr(atom_index);
-            ext_decl.fn_link.wasm.type_index = try func.bin_file.putOrGetFuncType(func_type);
+            ext_decl.fn_link.?.type_index = try func.bin_file.putOrGetFuncType(func_type);
             try func.bin_file.addOrUpdateImport(
                 mem.sliceTo(ext_decl.name, 0),
                 atom.getSymbolIndex().?,
                 ext_decl.getExternFn().?.lib_name,
-                ext_decl.fn_link.wasm.type_index,
+                ext_decl.fn_link.?.type_index,
             );
             break :blk extern_fn.data.owner_decl;
         } else if (func_val.castTag(.decl_ref)) |decl_ref| {

src/link.zig

@@ -261,39 +261,6 @@ pub const File = struct {
     /// of this linking operation.
     lock: ?Cache.Lock = null,
 
-    pub const LinkBlock = union {
-        elf: void,
-        coff: void,
-        macho: void,
-        plan9: void,
-        c: void,
-        wasm: void,
-        spirv: void,
-        nvptx: void,
-    };
-
-    pub const LinkFn = union {
-        elf: void,
-        coff: void,
-        macho: void,
-        plan9: void,
-        c: void,
-        wasm: Wasm.FnData,
-        spirv: void,
-        nvptx: void,
-    };
-
-    pub const Export = union {
-        elf: void,
-        coff: void,
-        macho: void,
-        plan9: void,
-        c: void,
-        wasm: void,
-        spirv: void,
-        nvptx: void,
-    };
-
     /// Attempts incremental linking, if the file already exists. If
     /// incremental linking fails, falls back to truncating the file and
     /// rewriting it. A malicious file is detected as incremental link failure

src/link/Wasm.zig

@@ -2829,7 +2829,7 @@ pub fn flushModule(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Nod
             if (decl.isExtern()) continue;
             const atom_index = entry.value_ptr.*;
             if (decl.ty.zigTypeTag() == .Fn) {
-                try wasm.parseAtom(atom_index, .{ .function = decl.fn_link.wasm });
+                try wasm.parseAtom(atom_index, .{ .function = decl.fn_link.? });
             } else if (decl.getVariable()) |variable| {
                 if (!variable.is_mutable) {
                     try wasm.parseAtom(atom_index, .{ .data = .read_only });