Sema: remove generic function from monomorphed_funcs on any error

Author: Vexu

src/Module.zig

@@ -3519,14 +3519,6 @@ pub fn deinit(mod: *Module) void {
 pub fn destroyDecl(mod: *Module, decl_index: Decl.Index) void {
     const gpa = mod.gpa;
     {
-        if (mod.failed_decls.contains(decl_index)) {
-            blk: {
-                const errs = mod.comp.getAllErrorsAlloc() catch break :blk;
-                for (errs.list) |err| Compilation.AllErrors.Message.renderToStdErr(err, .no_color);
-            }
-            // TODO restore test case triggering this panic
-            @panic("Zig compiler bug: attempted to destroy declaration with an attached error");
-        }
         const decl = mod.declPtr(decl_index);
         log.debug("destroy {*} ({s})", .{ decl, decl.name });
         _ = mod.test_functions.swapRemove(decl_index);

src/Sema.zig

@@ -7174,6 +7174,7 @@ fn instantiateGenericCall(
                 return err;
             },
             else => {
+                assert(mod.monomorphed_funcs.remove(new_module_func));
                 {
                     errdefer new_decl_arena.deinit();
                     try new_decl.finalizeNewArena(&new_decl_arena);

test/cases/compile_errors/generic_function_instantiation_inherits_parent_branch_quota.zig

@@ -0,0 +1,30 @@
+pub export fn entry1() void {
+    @setEvalBranchQuota(1001);
+    // Return type evaluation should inherit both the
+    // parent's branch quota and count meaning
+    // at least 2002 backwards branches are required.
+    comptime var i = 0;
+    inline while (i < 1000) : (i += 1) {}
+    _ = simple(10);
+}
+pub export fn entry2() void {
+    @setEvalBranchQuota(2001);
+    comptime var i = 0;
+    inline while (i < 1000) : (i += 1) {}
+    _ = simple(10);
+}
+fn simple(comptime n: usize) Type(n) {
+    return n;
+}
+fn Type(comptime n: usize) type {
+    if (n <= 1) return usize;
+    return Type(n - 1);
+}
+
+// error
+// backend=stage2
+// target=native
+//
+// :21:16: error: evaluation exceeded 1001 backwards branches
+// :21:16: note: use @setEvalBranchQuota() to raise the branch limit from 1001
+// :16:34: note: called from here