Canonicalize names of nested functions by keeping a more fine grained counter -- per (module, method name) pair (#53719)

As mentioned in #53716, we've
been noticing that `precompile` statements lists from one version of our
codebase often don't apply cleanly in a slightly different version.

That's because a lot of nested and anonymous function names have a
global numeric suffix which is incremented every time a new name is
generated, and these numeric suffixes are not very stable across
codebase changes.

To solve this, this PR makes the numeric suffixes a bit more fine
grained: every pair of (module, top-level/outermost function name) will
have its own counter, which should make nested function names a bit more
stable across different versions.

This PR applies @JeffBezanson's idea of making the symbol name changes
directly in `current-julia-module-counter`.

Here is an example:

```Julia
julia> function foo(x)
           function bar(y)
               return x + y
           end
       end
foo (generic function with 1 method)

julia> f = foo(42)
(::var"#bar#foo##0"{Int64}) (generic function with 1 method)
```

Author: d-netto

doc/src/manual/functions.md

@@ -292,12 +292,12 @@ syntaxes:
 
 ```jldoctest
 julia> x -> x^2 + 2x - 1
-#1 (generic function with 1 method)
+#2 (generic function with 1 method)
 
 julia> function (x)
            x^2 + 2x - 1
        end
-#3 (generic function with 1 method)
+#5 (generic function with 1 method)
 ```
 
 Each statement creates a function taking one argument `x` and returning the value of the polynomial `x^2 +

src/ast.c

@@ -7,6 +7,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+
 #ifdef _OS_WINDOWS_
 #include <malloc.h>
 #endif
@@ -215,11 +216,46 @@ static value_t fl_nothrow_julia_global(fl_context_t *fl_ctx, value_t *args, uint
         decode_restriction_value(pku) : jl_atomic_load_relaxed(&b->value)) != NULL ? fl_ctx->T : fl_ctx->F;
 }
 
-static value_t fl_current_module_counter(fl_context_t *fl_ctx, value_t *args, uint32_t nargs) JL_NOTSAFEPOINT
+// Used to generate a unique suffix for a given symbol (e.g. variable or type name)
+// first argument contains a stack of method definitions seen so far by `closure-convert` in flisp.
+// if the top of the stack is non-NIL, we use it to augment the suffix so that it becomes
+// of the form $top_level_method_name##$counter, where `counter` is the smallest integer
+// such that the resulting name is not already defined in the current module's bindings.
+// If the top of the stack is NIL, we simply return the current module's counter.
+// This ensures that precompile statements are a bit more stable across different versions
+// of a codebase. see #53719
+static value_t fl_module_unique_name(fl_context_t *fl_ctx, value_t *args, uint32_t nargs)
 {
+    argcount(fl_ctx, "julia-module-unique-name", nargs, 1);
     jl_ast_context_t *ctx = jl_ast_ctx(fl_ctx);
-    assert(ctx->module);
-    return fixnum(jl_module_next_counter(ctx->module));
+    jl_module_t *m = ctx->module;
+    assert(m != NULL);
+    // Get the outermost function name from the `parsed_method_stack` top
+    char *funcname = NULL;
+    value_t parsed_method_stack = args[0];
+    if (parsed_method_stack != fl_ctx->NIL) {
+        value_t bottom_stack_symbol = fl_applyn(fl_ctx, 1, symbol_value(symbol(fl_ctx, "last")), parsed_method_stack);
+        funcname = tosymbol(fl_ctx, bottom_stack_symbol, "julia-module-unique-name")->name;
+    }
+    size_t sz = funcname != NULL ? strlen(funcname) + 32 : 32; // 32 is enough for the suffix
+    char *buf = (char*)alloca(sz);
+    if (funcname != NULL && strchr(funcname, '#') == NULL) {
+        for (int i = 0; ; i++) {
+            snprintf(buf, sz, "%s##%d", funcname, i);
+            jl_sym_t *sym = jl_symbol(buf);
+            JL_LOCK(&m->lock);
+            if (jl_get_module_binding(m, sym, 0) == NULL) { // make sure this name is not already taken
+                jl_get_module_binding(m, sym, 1); // create the binding
+                JL_UNLOCK(&m->lock);
+                return symbol(fl_ctx, buf);
+            }
+            JL_UNLOCK(&m->lock);
+        }
+    }
+    else {
+        snprintf(buf, sz, "%d", jl_module_next_counter(m));
+    }
+    return symbol(fl_ctx, buf);
 }
 
 static int jl_is_number(jl_value_t *v)
@@ -252,7 +288,7 @@ static jl_value_t *scm_to_julia_(fl_context_t *fl_ctx, value_t e, jl_module_t *m
 static const builtinspec_t julia_flisp_ast_ext[] = {
     { "defined-julia-global", fl_defined_julia_global }, // TODO: can we kill this safepoint
     { "nothrow-julia-global", fl_nothrow_julia_global },
-    { "current-julia-module-counter", fl_current_module_counter },
+    { "current-julia-module-counter", fl_module_unique_name },
     { "julia-scalar?", fl_julia_scalar },
     { NULL, NULL }
 };

src/datatype.c

@@ -20,23 +20,21 @@ extern "C" {
 
 // allocating TypeNames -----------------------------------------------------------
 
-static int is10digit(char c) JL_NOTSAFEPOINT
-{
-    return (c >= '0' && c <= '9');
-}
-
 static jl_sym_t *jl_demangle_typename(jl_sym_t *s) JL_NOTSAFEPOINT
 {
     char *n = jl_symbol_name(s);
     if (n[0] != '#')
         return s;
-    char *end = strrchr(n, '#');
+    char *end = strchr(&n[1], '#');
+    // handle `#f...##...#...`
+    if (end != NULL && end[1] == '#')
+        end = strchr(&end[2], '#');
     int32_t len;
-    if (end == n || end == n+1)
+    if (end == NULL || end == n+1)
         len = strlen(n) - 1;
     else
         len = (end-n) - 1;  // extract `f` from `#f#...`
-    if (is10digit(n[1]))
+    if (isdigit(n[1]) || is_canonicalized_anonfn_typename(n))
         return _jl_symbol(n, len+1);
     return _jl_symbol(&n[1], len);
 }

src/flisp/flisp.h

@@ -158,7 +158,7 @@ value_t fl_cons(fl_context_t *fl_ctx, value_t a, value_t b) JL_NOTSAFEPOINT;
 value_t fl_list2(fl_context_t *fl_ctx, value_t a, value_t b) JL_NOTSAFEPOINT;
 value_t fl_listn(fl_context_t *fl_ctx, size_t n, ...) JL_NOTSAFEPOINT;
 value_t symbol(fl_context_t *fl_ctx, const char *str) JL_NOTSAFEPOINT;
-char *symbol_name(fl_context_t *fl_ctx, value_t v);
+char *symbol_name(fl_context_t *fl_ctx, value_t v) JL_NOTSAFEPOINT;
 int fl_is_keyword_name(const char *str, size_t len);
 value_t alloc_vector(fl_context_t *fl_ctx, size_t n, int init);
 size_t llength(value_t v);