Auto merge of rust-lang#87712 - est31:line-column-1-based, r=petrochenkov

Proc macro spans: make columns 1 based

This makes proc macro spans consistent with the `column!()` macro as well as `std::panic::Location`, as both are 1-based.

rust-lang#54725 (comment)

Author: bors

proc_macro/src/lib.rs

@@ -348,13 +348,13 @@ impl Span {
     /// Gets the starting line/column in the source file for this span.
     #[unstable(feature = "proc_macro_span", issue = "54725")]
     pub fn start(&self) -> LineColumn {
-        self.0.start()
+        self.0.start().add_1_to_column()
     }
 
     /// Gets the ending line/column in the source file for this span.
     #[unstable(feature = "proc_macro_span", issue = "54725")]
     pub fn end(&self) -> LineColumn {
-        self.0.end()
+        self.0.end().add_1_to_column()
     }
 
     /// Creates a new span encompassing `self` and `other`.
@@ -432,12 +432,18 @@ pub struct LineColumn {
     /// The 1-indexed line in the source file on which the span starts or ends (inclusive).
     #[unstable(feature = "proc_macro_span", issue = "54725")]
     pub line: usize,
-    /// The 0-indexed column (in UTF-8 characters) in the source file on which
-    /// the span starts or ends (inclusive).
+    /// The 1-indexed column (number of bytes in UTF-8 encoding) in the source
+    /// file on which the span starts or ends (inclusive).
     #[unstable(feature = "proc_macro_span", issue = "54725")]
     pub column: usize,
 }
 
+impl LineColumn {
+    fn add_1_to_column(self) -> Self {
+        LineColumn { line: self.line, column: self.column + 1 }
+    }
+}
+
 #[unstable(feature = "proc_macro_span", issue = "54725")]
 impl !Send for LineColumn {}
 #[unstable(feature = "proc_macro_span", issue = "54725")]