Show the right fct name in type error messages

crates/compiler/constrain/src/expr.rs

@@ -502,6 +502,7 @@ pub fn constrain_expr(
                 let reason = Reason::FnArg {
                     name: opt_symbol,
                     arg_index: HumanIndex::zero_based(index),
+                    called_via: *called_via,
                 };
                 let expected_arg =
                     constraints.push_expected_type(ForReason(reason, arg_type_index, region));

crates/compiler/module/src/called_via.rs

@@ -102,6 +102,15 @@ pub enum UnaryOp {
     Not,
 }
 
+impl std::fmt::Display for UnaryOp {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            UnaryOp::Negate => write!(f, "-"),
+            UnaryOp::Not => write!(f, "!"),
+        }
+    }
+}
+
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum BinOp {
     // highest precedence

crates/compiler/types/src/types.rs

@@ -3370,6 +3370,7 @@ pub enum Reason {
     FnArg {
         name: Option<Symbol>,
         arg_index: HumanIndex,
+        called_via: CalledVia,
     },
     TypedArg {
         name: Option<Symbol>,

crates/repl_test/src/tests.rs

@@ -658,17 +658,17 @@ fn too_few_args() {
 
 #[cfg(not(feature = "wasm"))] // TODO: mismatch is due to terminal control codes!
 #[test]
-fn type_problem() {
+fn type_problem_function() {
     expect_failure(
-        "1 + \"\"",
+        "Num.add 1 \"not a num\"",
         indoc!(
             r#"
                 ── TYPE MISMATCH ───────────────────────────────────────────────────────────────
 
                 This 2nd argument to add has an unexpected type:
 
-                4│      1 + ""
-                            ^^
+                4│      Num.add 1 "not a num"
+                                  ^^^^^^^^^^^
 
                 The argument is a string of type:
 
@@ -682,6 +682,84 @@ fn type_problem() {
     );
 }
 
+#[cfg(not(feature = "wasm"))] // TODO: mismatch is due to terminal control codes!
+#[test]
+fn type_problem_binary_operator() {
+    expect_failure(
+        "1 + \"\"",
+        indoc!(
+            r#"
+                ── TYPE MISMATCH ───────────────────────────────────────────────────────────────
+
+                This 2nd argument to + has an unexpected type:
+
+                4│      1 + ""
+                            ^^
+
+                The argument is a string of type:
+
+                    Str
+
+                But + needs its 2nd argument to be:
+
+                    Num *
+                "#
+        ),
+    );
+}
+
+#[cfg(not(feature = "wasm"))] // TODO: mismatch is due to terminal control codes!
+#[test]
+fn type_problem_unary_operator() {
+    expect_failure(
+        "!\"not a bool\"",
+        indoc!(
+            r#"
+                ── TYPE MISMATCH ───────────────────────────────────────────────────────────────
+
+                This 1st argument to ! has an unexpected type:
+
+                4│      !"not a bool"
+                         ^^^^^^^^^^^^
+
+                The argument is a string of type:
+
+                    Str
+
+                But ! needs its 1st argument to be:
+
+                    Bool
+                "#
+        ),
+    );
+}
+
+#[cfg(not(feature = "wasm"))] // TODO: mismatch is due to terminal control codes!
+#[test]
+fn type_problem_string_interpolation() {
+    expect_failure(
+        "\"This is not a string -> \\(1)\"",
+        indoc!(
+            r#"
+                ── TYPE MISMATCH ───────────────────────────────────────────────────────────────
+
+                This argument to this string interpolation has an unexpected type:
+
+                4│      "This is not a string -> \(1)"
+                                                   ^
+
+                The argument is a number of type:
+
+                    Num *
+
+                But this string interpolation needs its argument to be:
+
+                    Str
+                "#
+        ),
+    );
+}
+
 #[test]
 fn issue_2149_i8_ok() {
     expect_success(r#"Str.toI8 "127""#, "Ok 127 : Result I8 [InvalidNumStr]");

crates/reporting/src/error/type.rs

@@ -1273,12 +1273,24 @@ fn to_expr_report<'b>(
                     }
                 }
             },
-            Reason::FnArg { name, arg_index } => {
+            Reason::FnArg {
+                name,
+                arg_index,
+                called_via,
+            } => {
                 let ith = arg_index.ordinal();
 
-                let this_function = match name {
-                    None => alloc.text("this function"),
-                    Some(symbol) => alloc.symbol_unqualified(symbol),
+                let this_function = match (called_via, name) {
+                    (CalledVia::Space, Some(symbole)) => alloc.symbol_unqualified(symbole),
+                    (CalledVia::BinOp(op), _) => alloc.binop(op),
+                    (CalledVia::UnaryOp(op), _) => alloc.unop(op),
+                    (CalledVia::StringInterpolation, _) => alloc.text("this string interpolation"),
+                    _ => alloc.text("this function"),
+                };
+
+                let argument = match called_via {
+                    CalledVia::StringInterpolation => "argument".to_string(),
+                    _ => format!("{ith} argument"),
                 };
 
                 report_mismatch(
@@ -1292,7 +1304,7 @@ fn to_expr_report<'b>(
                     region,
                     Some(expr_region),
                     alloc.concat([
-                        alloc.string(format!("This {ith} argument to ")),
+                        alloc.string(format!("This {argument} to ")),
                         this_function.clone(),
                         alloc.text(" has an unexpected type:"),
                     ]),
@@ -1300,7 +1312,7 @@ fn to_expr_report<'b>(
                     alloc.concat([
                         alloc.text("But "),
                         this_function,
-                        alloc.string(format!(" needs its {ith} argument to be:")),
+                        alloc.string(format!(" needs its {argument} to be:")),
                     ]),
                     None,
                 )

crates/reporting/src/report.rs

@@ -490,6 +490,13 @@ impl<'a> RocDocAllocator<'a> {
         self.text(content.to_string()).annotate(Annotation::BinOp)
     }
 
+    pub fn unop(
+        &'a self,
+        content: roc_module::called_via::UnaryOp,
+    ) -> DocBuilder<'a, Self, Annotation> {
+        self.text(content.to_string()).annotate(Annotation::UnaryOp)
+    }
+
     /// Turns off backticks/colors in a block
     pub fn type_block(
         &'a self,
@@ -843,6 +850,7 @@ pub enum Annotation {
     Structure,
     Symbol,
     BinOp,
+    UnaryOp,
     Error,
     GutterBar,
     LineNumber,
@@ -1027,6 +1035,9 @@ where
             BinOp => {
                 self.write_str(self.palette.alias)?;
             }
+            UnaryOp => {
+                self.write_str(self.palette.alias)?;
+            }
             Symbol => {
                 self.write_str(self.palette.variable)?;
             }
@@ -1075,9 +1086,9 @@ where
         match self.style_stack.pop() {
             None => {}
             Some(annotation) => match annotation {
-                Emphasized | Url | TypeVariable | Alias | Symbol | BinOp | Error | GutterBar
-                | Ellipsis | Typo | TypoSuggestion | ParserSuggestion | Structure | CodeBlock
-                | PlainText | LineNumber | Tip | Module | Header | Keyword => {
+                Emphasized | Url | TypeVariable | Alias | Symbol | BinOp | UnaryOp | Error
+                | GutterBar | Ellipsis | Typo | TypoSuggestion | ParserSuggestion | Structure
+                | CodeBlock | PlainText | LineNumber | Tip | Module | Header | Keyword => {
                     self.write_str(self.palette.reset)?;
                 }