vim-patch:8.2.4883: string interpolation only works in heredoc

Problem:    String interpolation only works in heredoc.
Solution:   Support interpolated strings.  Use syntax for heredoc consistent
            with strings, similar to C#. (closes vim/vim#10327)

https://github.com/vim/vim/commit/2eaef106e4a7fc9dc74a7e672b5f550ec1f9786e

Cherry-pick Test_Debugger_breakadd_expr() from Vim.

Co-authored-by: LemonBoy <thatlemon@gmail.com>

1 files changed, 32 insertions, 1 deletions

diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index b240c36977..f8a9326703 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -3100,8 +3100,13 @@ static int eval7(char **arg, typval_T *rettv, evalarg_T *const evalarg, bool wan
     ret = eval_option((const char **)arg, rettv, evaluate);
     break;
   // Environment variable: $VAR.
+  // Interpolated string: $"string" or $'string'.
   case '$':
-    ret = eval_env_var(arg, rettv, evaluate);
+    if ((*arg)[1] == '"' || (*arg)[1] == '\'') {
+      ret = eval_interp_string(arg, rettv, evaluate);
+    } else {
+      ret = eval_env_var(arg, rettv, evaluate);
+    }
     break;
 
   // Register contents: @r.
@@ -4053,6 +4058,32 @@ static int eval_lit_string(char **arg, typval_T *rettv, int evaluate)
   return OK;
 }
 
+int eval_interp_string(char **arg, typval_T *rettv, int evaluate)
+{
+  // *arg is on the '$' character.
+  (*arg)++;
+
+  rettv->v_type = VAR_STRING;
+
+  typval_T tv;
+  int ret;
+  if (**arg == '"') {
+    ret = eval_string(arg, &tv, evaluate);
+  } else {
+    ret = eval_lit_string(arg, &tv, evaluate);
+  }
+
+  if (ret == FAIL || !evaluate) {
+    return ret;
+  }
+
+  rettv->vval.v_string = eval_all_expr_in_str(tv.vval.v_string);
+
+  tv_clear(&tv);
+
+  return rettv->vval.v_string != NULL ? OK : FAIL;
+}
+
 /// @return  the function name of the partial.
 char *partial_name(partial_T *pt)
   FUNC_ATTR_PURE