Merge pull request #21182 from JuliaLang/jb/fix21178

fix #21178, lowering of static params with `<:T` syntax

Author: JeffBezanson

src/julia-syntax.scm

@@ -228,15 +228,16 @@
 
 ;; extract static parameter names from a (method ...) expression
 (define (method-expr-static-parameters m)
-  (if (eq? (car (caddr m)) 'block)
-      (let ((lst '()))
-        (pattern-replace
-         (pattern-set
-          (pattern-lambda (= v (call (core (-/ TypeVar)) (quote T) ...))
-                          (begin (set! lst (cons T lst)) __)))
-         (butlast (cdr (caddr m))))
-        (reverse! lst))
-      '()))
+  (let ((type-ex (caddr m)))
+    (if (eq? (car type-ex) 'block)
+        ;; extract ssavalue labels of sparams from the svec-of-sparams argument to `method`
+        (let ((sp-ssavals (cddr (last (last type-ex)))))
+          (map (lambda (a)  ;; extract T from (= v (call (core TypeVar) (quote T) ...))
+                 (cadr (caddr (caddr a))))
+               (filter (lambda (e)
+                         (and (pair? e) (eq? (car e) '=) (member (cadr e) sp-ssavals)))
+                       (cdr type-ex))))
+        '())))
 
 ;; expressions of the form a.b.c... where everything is a symbol
 (define (sym-ref? e)

test/core.jl

@@ -4782,3 +4782,8 @@ let a = Array{Core.TypeofBottom, 1}(2)
     @test a[1] == Union{}
     @test a == [Union{}, Union{}]
 end
+
+# issue #21178
+struct F21178{A,B} end
+b21178(::F1,::F2) where {B1,B2,F1<:F21178{B1,<:Any},F2<:F21178{B2}} = F1,F2,B1,B2
+@test b21178(F21178{1,2}(),F21178{1,2}()) == (F21178{1,2}, F21178{1,2}, 1, 1)