fix some cases of dot syntax lowering

fix #26739, error for `sum.[1]`
fix #26873, should have no error for `f."a"`

src/julia-syntax.scm

@@ -1738,12 +1738,12 @@
             `(fuse ,(to-lambda f args kws) ,args_))))
     (if (and (pair? e) (eq? (car e) '|.|))
         (let ((f (cadr e)) (x (caddr e)))
-          (cond ((or (eq? (car x) 'quote) (eq? (car x) 'inert) (eq? (car x) '$))
+          (cond ((or (atom? x) (eq? (car x) 'quote) (eq? (car x) 'inert) (eq? (car x) '$))
                  `(call (top getproperty) ,f ,x))
                 ((eq? (car x) 'tuple)
                  (make-fuse f (cdr x)))
                 (else
-                 (error (string "invalid syntax " (deparse e))))))
+                 (error (string "invalid syntax \"" (deparse e) "\"")))))
         (if (and (pair? e) (eq? (car e) 'call) (dotop? (cadr e)))
             (make-fuse (undotop (cadr e)) (cddr e))
             e)))

src/toplevel.c

@@ -641,9 +641,8 @@ jl_value_t *jl_toplevel_eval_flex(jl_module_t *m, jl_value_t *e, int fast, int e
             jl_error("syntax: malformed \".\" expression");
         jl_value_t *lhs = jl_exprarg(ex, 0);
         jl_value_t *rhs = jl_exprarg(ex, 1);
-        // ('.' f (tuple args...)) is a broadcast instead, which doesn't
-        // go through this fast path.
-        if (!jl_is_expr(rhs) || ((jl_expr_t*)rhs)->head != tuple_sym)
+        // only handle `a.b` syntax here
+        if (jl_is_quotenode(rhs) && jl_is_symbol(jl_fieldref(rhs,0)))
             return jl_eval_dot_expr(m, lhs, rhs, fast);
     }
     if (ptls->in_pure_callback) {

test/syntax.jl

@@ -939,8 +939,8 @@ g21054(>:) = >:2
 @test g21054(-) == -2
 
 # issue #21168
-@test Meta.lower(Main, :(a.[1])) == Expr(:error, "invalid syntax a.[1]")
-@test Meta.lower(Main, :(a.{1})) == Expr(:error, "invalid syntax a.{1}")
+@test Meta.lower(Main, :(a.[1])) == Expr(:error, "invalid syntax \"a.[1]\"")
+@test Meta.lower(Main, :(a.{1})) == Expr(:error, "invalid syntax \"a.{1}\"")
 
 # Issue #21225
 let abstr = Meta.parse("abstract type X end")
@@ -1406,3 +1406,16 @@ invalid assignment location "function (s, o...)
     end
 end\""""
 end
+
+# issue #26739
+@test_throws ErrorException("syntax: invalid syntax \"sin.[1]\"") eval(@__MODULE__, :(sin.[1]))
+
+# issue #26873
+f26873 = 0
+try
+    include_string(@__MODULE__, """f26873."a" """)
+    @test false
+catch e
+    @test e isa LoadError
+    @test e.error isa MethodError
+end