Slightly improve error messages.

Author: peterhuene

crates/wac-parser/src/resolution.rs

@@ -682,25 +682,27 @@ pub enum Error {
         span: SourceSpan,
     },
     /// An import is not in the target world.
-    #[error("import `{name}` is not present in target world `{world}`")]
+    #[error("target world `{world}` does not have an import named `{name}`")]
     ImportNotInTarget {
         /// The import name.
         name: String,
         /// The target world.
         world: String,
         /// The span where the error occurred.
-        #[label(primary, "import `{name}` is not in the target world")]
+        #[label(primary, "cannot have an import named `{name}`")]
         span: SourceSpan,
     },
     /// Missing an export for the target world.
-    #[error("missing export `{name}` for target world `{world}`")]
+    #[error("target world `{world}` requires an export named `{name}`")]
     MissingTargetExport {
         /// The export name.
         name: String,
+        /// The expected item kind.
+        kind: String,
         /// The target world.
         world: String,
         /// The span where the error occurred.
-        #[label(primary, "must export `{name}` to target this world")]
+        #[label(primary, "must export a {kind} named `{name}` to target this world")]
         span: SourceSpan,
     },
     /// An import or export has a mismatched type for the target world.

crates/wac-parser/src/resolution/ast.rs

@@ -2305,6 +2305,7 @@ impl<'a> AstResolver<'a> {
                 .ok_or_else(|| Error::MissingTargetExport {
                     name: name.clone(),
                     world: path.string.to_owned(),
+                    kind: expected.as_str(&self.definitions).to_string(),
                     span: path.span,
                 })?;
 

crates/wac-parser/tests/resolution/fail/missing-target-export.wac.result

@@ -1,8 +1,8 @@
 failed to resolve document
 
-  × missing export `hello` for target world `foo:bar/baz`
+  × target world `foo:bar/baz` requires an export named `hello`
    ╭─[tests/resolution/fail/missing-target-export.wac:1:27]
  1 │ package test:comp targets foo:bar/baz;
    ·                           ─────┬─────
-   ·                                ╰── must export `hello` to target this world
+   ·                                ╰── must export a function named `hello` to target this world
    ╰────

crates/wac-parser/tests/resolution/fail/target-extraneous-import.wac.result

@@ -1,9 +1,9 @@
 failed to resolve document
 
-  × import `bar` is not present in target world `test:comp/foo`
+  × target world `test:comp/foo` does not have an import named `bar`
    ╭─[tests/resolution/fail/target-extraneous-import.wac:7:8]
  6 │ 
  7 │ import bar: func();
    ·        ─┬─
-   ·         ╰── import `bar` is not in the target world
+   ·         ╰── cannot have an import named `bar`
    ╰────