Improve checks for postfix suggestions

crates/ide/src/completion/complete_postfix.rs

@@ -211,9 +211,7 @@ pub(super) fn complete_postfix(acc: &mut Completions, ctx: &CompletionContext) {
     )
     .add_to(acc);
 
-    if ctx.is_string_literal {
-        add_format_like_completions(acc, ctx, &dot_receiver, cap, &receiver_text);
-    }
+    add_format_like_completions(acc, ctx, &dot_receiver, cap, &receiver_text);
 }
 
 fn get_receiver_text(receiver: &ast::Expr, receiver_is_ambiguous_float_literal: bool) -> String {

crates/ide/src/completion/complete_postfix/format_like.rs

@@ -27,7 +27,11 @@ pub(super) fn add_format_like_completions(
     cap: SnippetCap,
     receiver_text: &str,
 ) {
-    assert!(receiver_text.len() >= 2);
+    if !is_string_literal(receiver_text) {
+        // It's not a string literal, do not parse input.
+        return;
+    }
+
     let input = &receiver_text[1..receiver_text.len() - 1];
 
     let mut parser = FormatStrParser::new(input);
@@ -42,6 +46,20 @@ pub(super) fn add_format_like_completions(
     }
 }
 
+/// Checks whether provided item is a string literal.
+fn is_string_literal(item: &str) -> bool {
+    if item.len() < 2 {
+        return false;
+    }
+    if item.chars().nth(0) != Some('"') || item.chars().nth(item.len() - 1) != Some('"') {
+        return false;
+    }
+
+    true
+}
+
+/// Parser for a format-like string. It is more allowing in terms of string contents,
+/// as we expect variable placeholders to be filled with expressions.
 #[derive(Debug)]
 pub struct FormatStrParser {
     input: String,
@@ -127,7 +145,7 @@ impl FormatStrParser {
     pub fn parse(&mut self) -> Result<(), ()> {
         let mut current_expr = String::new();
 
-        let mut placeholders_count = 0;
+        let mut placeholder_id = 1;
 
         // Count of open braces inside of an expression.
         // We assume that user knows what they're doing, thus we treat it like a correct pattern, e.g.
@@ -163,8 +181,8 @@ impl FormatStrParser {
                 (State::MaybeExpr, '}') => {
                     // This is an empty sequence '{}'. Replace it with placeholder.
                     self.output.push(chr);
-                    self.extracted_expressions.push(format!("${}", placeholders_count));
-                    placeholders_count += 1;
+                    self.extracted_expressions.push(format!("${}", placeholder_id));
+                    placeholder_id += 1;
                     self.state = State::NotExpr;
                 }
                 (State::MaybeExpr, _) => {

crates/ide/src/completion/completion_context.rs

@@ -74,8 +74,6 @@ pub(crate) struct CompletionContext<'a> {
     pub(super) is_pattern_call: bool,
     /// If this is a macro call, i.e. the () are already there.
     pub(super) is_macro_call: bool,
-    /// If this is a string literal, like "lorem ipsum".
-    pub(super) is_string_literal: bool,
     pub(super) is_path_type: bool,
     pub(super) has_type_args: bool,
     pub(super) attribute_under_caret: Option<ast::Attr>,
@@ -158,7 +156,6 @@ impl<'a> CompletionContext<'a> {
             is_call: false,
             is_pattern_call: false,
             is_macro_call: false,
-            is_string_literal: false,
             is_path_type: false,
             has_type_args: false,
             dot_receiver_is_ambiguous_float_literal: false,
@@ -473,12 +470,6 @@ impl<'a> CompletionContext<'a> {
                 } else {
                     false
                 };
-
-            self.is_string_literal = if let Some(ast::Expr::Literal(l)) = &self.dot_receiver {
-                matches!(l.kind(), ast::LiteralKind::String { .. })
-            } else {
-                false
-            };
         }
         if let Some(method_call_expr) = ast::MethodCallExpr::cast(parent) {
             // As above