Sema: explain why comptime is needed

src/Module.zig

@@ -4065,18 +4065,6 @@ pub fn semaFile(mod: *Module, file: *File) SemaError!void {
         var wip_captures = try WipCaptureScope.init(gpa, new_decl_arena_allocator, null);
         defer wip_captures.deinit();
 
-        var block_scope: Sema.Block = .{
-            .parent = null,
-            .sema = &sema,
-            .src_decl = new_decl_index,
-            .namespace = &struct_obj.namespace,
-            .wip_capture_scope = wip_captures.scope,
-            .instructions = .{},
-            .inlining = null,
-            .is_comptime = true,
-        };
-        defer block_scope.instructions.deinit(gpa);
-
         if (sema.analyzeStructDecl(new_decl, main_struct_inst, struct_obj)) |_| {
             try wip_captures.finalize();
             new_decl.analysis = .complete;
@@ -4185,7 +4173,7 @@ fn semaDecl(mod: *Module, decl_index: Decl.Index) !bool {
     const result_ref = (try sema.analyzeBodyBreak(&block_scope, body)).?.operand;
     try wip_captures.finalize();
     const src = LazySrcLoc.nodeOffset(0);
-    const decl_tv = try sema.resolveInstValue(&block_scope, src, result_ref);
+    const decl_tv = try sema.resolveInstValue(&block_scope, .unneeded, result_ref, undefined);
     const decl_align: u32 = blk: {
         const align_ref = decl.zirAlignRef();
         if (align_ref == .none) break :blk 0;
@@ -4194,7 +4182,7 @@ fn semaDecl(mod: *Module, decl_index: Decl.Index) !bool {
     const decl_linksection: ?[*:0]const u8 = blk: {
         const linksection_ref = decl.zirLinksectionRef();
         if (linksection_ref == .none) break :blk null;
-        const bytes = try sema.resolveConstString(&block_scope, src, linksection_ref);
+        const bytes = try sema.resolveConstString(&block_scope, src, linksection_ref, "linksection must be comptime known");
         break :blk (try decl_arena_allocator.dupeZ(u8, bytes)).ptr;
     };
     const target = sema.mod.getTarget();

test/cases/compile_errors/asm_at_compile_time.zig

@@ -14,5 +14,5 @@ fn doSomeAsm() void {
 // backend=llvm
 // target=native
 //
-// :6:5: error: unable to resolve comptime value
+// :6:5: error: unable to evalutate comptime expression
 // :2:14: note: called from here

test/cases/compile_errors/call method on bound fn referring to var instance.zig

@@ -17,4 +17,4 @@ fn bad(ok: bool) void {
 // target=native
 // backend=stage2
 //
-// :12:18: error: unable to resolve comptime value
+// :12:18: error: cannot load runtime value in comptime block

test/cases/compile_errors/int-float_conversion_to_comptime_int-float.zig

@@ -12,4 +12,6 @@ export fn bar() void {
 // target=native
 //
 // :3:35: error: unable to resolve comptime value
+// :3:35: note: value being casted to 'comptime_int' must be comptime known
 // :7:37: error: unable to resolve comptime value
+// :7:37: note: value being casted to 'comptime_float' must be comptime known

test/cases/compile_errors/non-const_expression_function_call_with_struct_return_value_outside_function.zig

@@ -14,5 +14,5 @@ export fn entry() usize { return @sizeOf(@TypeOf(a)); }
 // backend=stage2
 // target=native
 //
-// :6:26: error: unable to resolve comptime value
+// :6:26: error: cannot store to runtime value in comptime block
 // :4:17: note: called from here

test/cases/compile_errors/non-pure_function_returns_type.zig

@@ -21,5 +21,5 @@ export fn function_with_return_type_type() void {
 // backend=stage2
 // target=native
 //
-// :3:7: error: unable to resolve comptime value
+// :3:7: error: cannot load runtime value in comptime block
 // :16:19: note: called from here

test/cases/compile_errors/non_constant_expression_in_array_size.zig

@@ -10,5 +10,5 @@ export fn entry() usize { return @offsetOf(Foo, "y"); }
 // backend=stage2
 // target=native
 //
-// :5:25: error: unable to resolve comptime value
+// :5:25: error: cannot load runtime value in comptime block
 // :2:15: note: called from here

test/cases/extern_variable_has_no_type.0.zig

@@ -6,4 +6,4 @@ extern var foo: i32;
 
 // error
 //
-// :2:15: error: unable to resolve comptime value
+// :2:15: error: cannot load runtime value in comptime block

test/cases/x86_64-linux/assert_function.8.zig

@@ -22,3 +22,4 @@ pub fn assert(ok: bool) void {
 // error
 //
 // :3:21: error: unable to resolve comptime value
+// :3:21: note: condition in comptime branch must be comptime known

test/stage2/cbe.zig

@@ -51,8 +51,8 @@ pub fn addCases(ctx: *TestContext) !void {
             \\}
             \\var y: @import("std").builtin.CallingConvention = .C;
         , &.{
-            ":2:22: error: unable to resolve comptime value",
-            ":5:26: error: unable to resolve comptime value",
+            ":2:22: error: cannot load runtime value in comptime block",
+            ":5:26: error: cannot load runtime value in comptime block",
         });
     }