don't transform typed bracket exprs to `[]` calls in templates (#23175)

fixes #22775

It's pre-existing that [`prepareOperand` doesn't typecheck expressions
which have
types](https://github.com/nim-lang/Nim/blob/a4f3bf374238df96f0982b7106e3702da6b485b1/compiler/sigmatch.nim#L2444).
Templates can take typed subscript expressions, transform them into
calls to `[]`, and then have this `[]` not be resolved later if the
expression is nested inside of a call argument, which leaks an untyped
expression past semantic analysis. To prevent this, don't transform any
typed subscript expressions into calls to `[]` in templates. Ditto for
curly subscripts (with `{}`) and assignments to subscripts and curly
subscripts (with `[]=` and `{}=`).

1 files changed, 38 insertions, 0 deletions

diff --git a/tests/template/tnested.nim b/tests/template/tnested.nim
new file mode 100644
index 000000000..81e416a76
--- /dev/null
+++ b/tests/template/tnested.nim
@@ -0,0 +1,38 @@
+block: # issue #22775
+  proc h(c: int) = discard
+  template k(v: int) =
+    template p() = v.h()
+    p()
+  let a = @[0]
+  k(0 and not a[0])
+
+block: # issue #22775 case 2
+  proc h(c: int, q: int) = discard
+  template k(v: int) =
+    template p() = h(v, v)
+    p()
+  let a = [0]
+  k(0 and not a[0])
+
+block: # issue #22775 minimal cases
+  proc h(c: int) = discard
+  template k(v: int) =
+    template p() = h(v)
+    p()
+  let a = [0]
+  k(not a[0])
+  block:
+    k(-a[0])
+  block:
+    proc f(x: int): int = x
+    k(f a[0])
+
+block: # bracket assignment case of above tests
+  proc h(c: int) = discard
+  template k(v: int) =
+    template p() = h(v)
+    p()
+  var a = [0]
+  k(not (block:
+    a[0] = 1
+    1))