Sema: cleanup `coerceExtra`

 * remove unreachable code
 * remove already handled cases
 * avoid `InternPool.getCoerced`
 * add some undef checks
 * error when converting undef int to float

Closes #16987

2 files changed, 14 insertions, 0 deletions

diff --git a/test/behavior/cast.zig b/test/behavior/cast.zig
index 85d1b28a5a..482720d228 100644
--- a/test/behavior/cast.zig
+++ b/test/behavior/cast.zig
@@ -1155,6 +1155,8 @@ fn foobar(func: PFN_void) !void {
 }
 
 test "cast function with an opaque parameter" {
+    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
+
     const Container = struct {
         const Ctx = opaque {};
         ctx: *Ctx,
@@ -2494,3 +2496,14 @@ test "@intFromBool on vector" {
     try S.doTheTest();
     try comptime S.doTheTest();
 }
+
+test "numeric coercions with undefined" {
+    if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
+
+    const from: i32 = undefined;
+    var to: f32 = from;
+    to = @floatFromInt(from);
+    to = 42.0;
+    try expectEqual(@as(f32, 42.0), to);
+}
diff --git a/test/behavior/undefined.zig b/test/behavior/undefined.zig
index 6c99b4bbce..9f134b315f 100644
--- a/test/behavior/undefined.zig
+++ b/test/behavior/undefined.zig
@@ -1,6 +1,7 @@
 const std = @import("std");
 const builtin = @import("builtin");
 const expect = std.testing.expect;
+const expectEqual = std.testing.expectEqual;
 const mem = std.mem;
 
 fn initStaticArray() [10]i32 {