Prevent analysis of functions only referenced at comptime

The idea here is that there are two ways we can reference a function at runtime:

* Through a direct call, i.e. where the function is comptime-known
* Through a function pointer

This means we can easily perform a form of rudimentary escape analysis
on functions. If we ever see a `decl_ref` or `ref` of a function, we
have a function pointer, which could "leak" into runtime code, so we
emit the function; but for a plain `decl_val`, there's no need to.

This change means that `comptime { _ = f; }` no longer forces a function
to be emitted, which was used for some things (mainly tests). These use
sites have been replaced with `_ = &f;`, which still triggers analysis
of the function body, since you're taking a pointer to the function.

Resolves: #6256
Resolves: #15353

1 files changed, 2 insertions, 2 deletions

diff --git a/test/cases/compile_errors/noalias_on_non_pointer_param.zig b/test/cases/compile_errors/noalias_on_non_pointer_param.zig
index 806808820f..65e6e141ce 100644
--- a/test/cases/compile_errors/noalias_on_non_pointer_param.zig
+++ b/test/cases/compile_errors/noalias_on_non_pointer_param.zig
@@ -2,10 +2,10 @@ fn f(noalias x: i32) void { _ = x; }
 export fn entry() void { f(1234); }
 
 fn generic(comptime T: type, noalias _: [*]T, noalias _: [*]const T, _: usize) void  {}
-comptime { _ = generic; }
+comptime { _ = &generic; }
 
 fn slice(noalias _: []u8) void  {}
-comptime { _ = slice; }
+comptime { _ = &slice; }
 
 // error
 // backend=stage2